The Keto Diet Credo: Answer to Your Prayers or Nutrition Nightmare?
“Ketomania” is sweeping the globe, as more and more people claim their ketogenic diet plan is the best thing since sliced bread (but no more bread for you!). Is keto all it’s cracked up to be? Does keto work, how does keto work, and for what? How to start a keto diet get great results, safely? Not to fear, the Captain’s Crew is here to answer all those questions and more!
What is Ketosis anyway?
Ketosis is one of the human body’s most important hard-wired survival modes, designed to provide fuel to the brain during starvation. By fasting, or by consuming a diet very low in carbohydrates (less than 50g/day), the ketosis system can essentially be hacked. On average, this takes 3-4 days. As such, your body can maintain a constant state of ketosis without triggering other metabolic emergency switches associated with true starvation, which may be harmful in the long term.
Under normal conditions, your body’s preferred sources of fuel are glucose and fatty acids — glucose being the simplest form of sugar (a.k.a. carbohydrate) and fatty acids being the common currency of fat molecules. Note that, on a molecular level, both carbohydrates and fatty acids are made of carbon (C), hydrogen (H) and oxygen (O). Glucose tends to be used for quick-burning applications such as a sprint or power lift, whereas fat utilization occurs for sustained output such as a long walk or run. Fats ultimately yield more than twice as much energy as carbs (per gram), but the process takes longer. Protein can also be used to produce energy, whereby certain amino acids (protein building blocks) are converted to glucose, but this process is extremely inefficient and therefore only able to fulfill minor demands.
Your muscles have numerous different ways of producing the energy they need, including the use of blood glucose directly, breaking down stored glucose (glycogen) locally or by burning fat. Cells and tissues within the central nervous system (CNS) handle their energy needs a little differently, however, in at least two key ways. One, the CNS cannot store glucose as glycogen. And two, fatty acids cannot be imported as a fuel source as they are unable to cross the blood-brain barrier — a filtration system designed to protect the brain and spinal cord from toxins. Instead, a constant supply of glucose must be delivered to the CNS — unless of course, the body’s supply of glucose runs short for some reason. In the absence of sufficient glucose, ketogenesis kicks in to produce yet another set of carbon-hydrogen-oxygen molecules called ketone bodies or ketones, which may travel from the liver, cross the blood-brain barrier and fuel the brain, just like glucose does.
Keep in mind that a small amount of ketogenesis occurs all the time, but your body is not technically in “ketosis” unless significant numbers of ketones spill out into your blood and urine. More about this later in the section about measuring ketosis …
In the ketosis pathway, fatty acids undergo a chemical reaction in your liver to form acetoacetate (C4H6O3), which is a very unstable ketone. As a result, most acetoacetate is either spontaneously degraded to acetone (C3H6O) or enzymatically converted to beta-hydroxybutyrate (C4H8O3). Given that acetone is used as an industrial solvent, and is the active ingredient in nail polish remover, your body doesn’t have much use for it, so it’s dumped off via urine and exhaled breath. The latter often has a slightly sweet or fruity odor and is one of the tell-tale signs your body is either in ketosis or ketoacidosis, which are not the same and will be discussed in further detail shortly. The beta-hydroxybutyrate ketones are the good stuff, which can be distributed all over your body, including your brain, to provide energy in lieu of glucose (1, 2, 3).
If you’re a science nerd and would enjoy a full explanation of the physiology of ketosis, check out this video.
Not to be confused with ketoacidosis
Again, you can think about ketosis as an emergency backup system, like a gas generator that seamlessly provides power to your house when the electric grid fails. Hopefully, apart from maybe a flicker of lights, you won’t even notice. Well, by contrast, imagine ketoacidosis like a tornado siren warning you that possible death and destruction are headed your way!
In ketoacidosis, ketone levels in the blood are typically 2-3 times greater than even the most advanced phases of nutritional ketosis. Moreover, for various reasons the body has a difficult time utilizing them or otherwise disposing of them in a timely manner, making the person very sick. Common symptoms include (4):
- Excessive thirst
- Frequent urination
- Nausea and vomiting
- Abdominal pain
- Weakness or fatigue
- Shortness of breath
- Fruity-scented breath
The good news is unless you have diabetes, your risk of ever suffering ketoacidosis is very low. Most cases occur in those with type 1 diabetes, who are completely dependent on insulin to control their blood sugar — and who stop taking insulin and/or contract a secondary illness such as the flu or pneumonia, which can impair the function of insulin.
Ketogenic diets, then and now
High fat, low carbohydrate diets were originally used to treat epilepsy at the Mayo Clinic, as early as 1921. In the decades to follow, it gained favor with other medical centers such as Johns Hopkins, based on its demonstrated ability to help prevent seizures in children (5, 6).
The classic ketogenic diet plan is defined by it’s 4-to-1 ratio (4:1) of fat to carbohydrates plus protein, as measured in grams. In other words, you eat four times as much fat as you do carbohydrates and protein combined. This comes as a surprise to a lot of people, because they assume keto means you can have as much protein as you want, as long as carbs are restricted. Indeed, there are variants of keto that allow for more protein, but not in the classic keto meal plan.
In terms of calories and percentages, which is the way diets are typically described nowadays, this 4:1 ratio equates to 9:1. That is, your classic keto diet is 90% fat calories, while the remaining 10% is carbs and protein. Needless to say, this is a far cry from the orthodox advice given my most health and nutrition authorities, to consume no more than 30% of calories from fat (7).
To say the “ketogenic diet” has been widely interpreted and modified in recent years would be quite an understatement. Apart from the carbohydrate restriction, there tends to be little agreement about the best type of keto diet — and to be fair, this is probably because there’s NOT one optimal way to go keto. Not for everyone. What may work for you may not work for your brother, mother or best friend. The right fit will depend on many factors including your goals, health status, and personal food preferences.
Keto 2.0, Modern Variations on the classic
Let’s face it, consuming 90% of your calories as fat is no easy feat, any way you slice it. Therefore it’s no surprise that the definition of keto has been massaged and stretched in so many different ways, in order to make the diet easier to follow. For researchers, this brings the advantage of less dropouts from their experimental groups, and thus more statistical power to their studies. For marketers, authors, nutrition bloggers and the like, it means their offerings will appeal to a wider audience — and translate to more inspiring testimonials. Unfortunately, for the average person out there, it often means more confusion — so let’s break it all down, taking the most legitimate versions of the ketogenic diet one by one.
MCT Oil diet
Within the classic keto structure is a variant that incorporates medium-chain triglyceride (MCT) oil for a significant portion of the fat consumed. MCTs are metabolized in a more direct pathway than standard long-chain dietary fats — as they’re sent directly to the liver as opposed to entering the lymphatic system first. As a result, they are able to produce more ketones and thus reduce the total amount of fat required to maintain ketosis, although the exact amount of reduction may vary widely from person to person.
Aside from this advantage, MCTs have also been shown to promote healthier cholesterol profiles as compared to saturated fats, with high cholesterol of course being a major risk factor for cardiovascular disease. The main drawback of relying on MCT oil is that it’s expensive and not ideally suited for cooking, given it’s low smoke point. In terms of effectiveness, research shows the classic keto approach to be equally successful whether MCTs are used or not (8).
MCT oil diets may derive anywhere from 30-60% of total calories from MCT oil, depending on how aggressive an approach is desired and how well the MCT oil is tolerated. For many people, too much MCT oil will cause problems such as diarrhea, cramping or, in rare cases, nausea and vomiting. MCT oil contains about 130 calories per tablespoon, which means that for a diet totaling 1800 calories daily, 30% from MCT would equate to approximately four tablespoons, while 60% would be eight tablespoons. Again, the more MCT oil used means less fat needs to be consumed from other food sources such as butter, cream, and so on (9).
Modified Atkins diet
Cardiologist Robert Atkins began popularizing his low carb diet plan in the 1960s and 70s, and of course it eventually became a commercial juggernaut. There are now numerous different versions of Atkins tailored to different eating preferences and goals, but the overarching philosophy is extreme carb restriction — especially simple sugars — along with liberal intake of fats and protein.
For this reason, many still associate Atkins with eating as much bacon and other fatty foods as you want, though Atkins has evolved to embrace more of a Mediterranean style (i.e. lean meats, fish and healthy fats like olive oil). Atkins also helped mainstream the use of “net carbs” — which are defined in simplest terms as total carbs minus total fiber.
If you’re an insulin-dependent diabetic or otherwise wish to adopt a more precise method of counting net carbs, dietitian Madelyn L. Wheeler offers a detailed explanation here.
The classic Atkins plan suggests a limit of 20g net carbs per day for the first few weeks, followed by a gradual increase over subsequent months. Adjustments depend largely upon weight loss goals being reached and maintained. To be clear, the Atkins diet was not originally designed to be a ketogenic diet, per se, but purely a weight loss diet.
By contrast, the Modified Atkins diet is intended to achieve and maintain ketosis over time. Essentially you never leave Phase 1 of the classic plan, limiting net carbs to 20g per day for the duration of the diet, while eating protein and fat more or less freely. Although ideally your calories will be distributed as 65% fat, 25% protein and 10% carbs on Modified Atkins to maintain both ketosis and proper nutrition overall.
Liberalized Ketogenic diet
At the end of the day, just about any diet that includes less than 50 grams of net carbohydrates per day should be sufficient to reach and maintain ketosis. In other words, if you’re choosing keto for weight loss or some other general improvement in your health, both classic keto and modified Atkins are probably overkill.
Besides, they’re extremely hard to stick with for long periods of time, which is why most studies only last a year or two, at most. So when thinking about the other diet variants and the keto menu planning to follow, we suggest you make your daily carb goal 50 grams. Once you get going, it’s even possible you could maintain ketosis on as much as 80 grams, if you work up to it gradually.
Cyclical Ketogenic diet
This regimen alternates or “cycles” between keto days and non-keto days. In order to maintain adequate ketosis, the general recommendation is just one non-keto day per week, or a maximum of two if taken in succession (i.e., the weekend). The obvious advantage is that it helps prevent burnout on the keto menu, while the disadvantage is that your degree of ketosis will be lower on average, translating to diminished results (maybe).
Finally, keep in mind cyclical keto is not quite the same as carb cycling, which has also gained a lot of followers. Carb cycling also restricts carbs for 4-6 days a week, but usually not enough to promote nutritional ketosis (16).
Targeted Ketogenic diet
A favorite of fitness gurus, targeted keto is designed to enhance athletic performance by allowing a small amount of carbs prior to a workout or event. The theory is that these carbs will fuel the muscles directly during exertion without filling glycogen stores or significantly altering ketosis.
Keep in mind, this is a relatively untested, unstudied protocol, depending on a number of different factors for success. These include the strictness of your baseline keto diet and amount of carbs eaten prior to workout, not to mention the length and strenuousness of your workouts. So, needless to say, a lot of trial and error may be required for this one (17).
Intermittent fasting keto diet
This approach merges keto — however you may choose to do it — and intermittent fasting, which is really catching fire now as a weight loss program. There are two basic ways to do intermittent fasting. One way is to follow your normal dietary pattern for most of the week, typically six days, then fast for one full day — meaning you consume nothing but water and other sugar-free beverages (black coffee, tea, etc.) for hydration purposes.
The other more popular method, often called “time restricted eating,” does just that — you simply restrict your eating to a 6-12 hour time period and fast the remaining time. Thus far, research is suggesting a minimum of 14 hours fasting time daily for best results. For example, if you finish eating dinner by 7 pm, you would need to wait until at least 9 am for breakfast — or skip breakfast entirely (18).
Other pseudo-keto diets
Of course, there are dozens of popular low-carb diets that could result in mild ketosis, such as Paleo, Whole30, Dukan and South Beach, each with its own promotional hook. While they all have pros and cons, and may, in fact, help you achieve your particular health goals, they are not specifically designed to be ketogenic (19).
You may also choose to add more layers of restriction to any diet, based on your ethical or philosophical beliefs. Going “organic” or “clean” would be examples of this approach, and could be applied to any of the keto diet variants without undermining their effectiveness. Just don’t expect these add-ons to make keto more effective, safer or easier to sustain long-term.
Check out this video from Mayo Clinic for a “fair and balanced” discussion of ketogenic diets.
How to start a Keto diet
Before starting your ketogenic diet plan, it would be helpful to know what foods to eat on a keto diet, and what foods not to eat on keto — the natural place to start being carbohydrates. The first absolute NO to get through your head when starting keto is the “S” word — sugar. White sugar, brown sugar, powdered sugar — no, no, and no. Anything with a name that includes fructose, glucose, lactose, galactose, maltose or anything else ending in “ose” — nope. Same goes for names containing words like syrup (i.e. brown rice syrup), juice or nectar.
Forget about all those “natural” sweeteners too, like honey, maple and agave. Though keep in mind, if you’re considering packaged foods it’s really quite simple — just refer to where it says Total Carbohydrates on the label (subtracting fiber for net carbs) and decide whether the amount and serving size makes sense within your carb budget. Again, the amount of carbohydrates you allow yourself may vary, from say 20-50 g/day, depending on the type of keto diet being followed — and yes, you may subtract fiber to calculate net carbs.
Bottom line though, your plan will be a whole lot simpler, not to mention more nutritious, if the majority of your diet comes from whole foods — that is, natural stuff with minimal processing by humankind.
Which foods are high in carbohydrates?
- Grains such as wheat, rye, barley, quinoa, oats, rice, and many others. Foods made with grains include breads and other baked goods, cereals and pastas
- Beans and legumes, including chickpeas, lentils and split peas
- Dairy products such as milk, buttermilk and yogurt
- Dairy substitutes or “milks” from soy, hemp, nuts, coconut, oats or other grains
- Fruits and fruit juices
- Starchy vegetables, such as potatoes, corn and peas
- Nuts and seeds
Remember, you will not be reducing your carb intake to zero. As such, any of these foods are technically possible to eat, however some contain too many carbs for the portion size to be practical (i.e. one bite of potatoes). More about this shortly, but first let’s understand the other two macronutrients, proteins and fats.
Which foods are high in protein?
- Meat and Seafood of all kinds
Also, with the exception of fruits and starchy vegetables, all the carbohydrate foods listed above contain significant amounts of protein. But for that reason, they will not be viable as major sources of protein in a keto diet. Instead, the majority of your protein on keto will need to come from meat, seafood and eggs — along with protein powders (whey, soy, etc.) containing very little or no carbohydrates.
Which foods are high in fat?
- Plant-based oils including olive, coconut, flaxseed, avocado, peanut and many more.
- Cream specifically “heavy cream” or “heavy whipping cream”
- Sour cream
- Meat and Seafood of all kinds, but especially certain cuts of pork and red meat, along with fatty fish like salmon, mackerel and herring.
Again, most whole foods contain not one, but two or all three of the macronutrients in some detectable quantity. For example, among the high carbohydrate foods listed above, dairy products, dairy substitutes, nuts, and seeds may contain a significant portion of fat, too. Likewise, high protein foods like eggs and cheese contain some fat also.
What to know about fat, in particular, saturated fat
At nine calories per gram, fat is the most energy-dense of the three macronutrients — as compared to four calories per gram each for protein and carbohydrates. Fat comes in a variety of different forms including saturated, monounsaturated and polyunsaturated, along with further distinctions like long chain, medium chain and “omega-3,” all of which pertain to the chemical structure of the molecules themselves (fatty acids). Regardless though, all fatty acids basically look like chains of various lengths built mostly from carbon and hydrogen atoms with a couple of oxygen atoms stuck on the end.
Unsaturated fats have some open spaces on the carbon chain where hydrogens are missing, thus making them more flexible. Each of these spots contains a double-bond. Monounsaturated means there’s just one double bond, or unsaturated site, whereas polyunsaturated means there are two or more. Plant sources of fat contain different combinations of mono- and polyunsaturated fats, with some being much higher in one or the other. Generally speaking, both types are considered to be equally healthy fats.
Saturated fat is called such because, on a molecular level, all its carbon atoms are saturated with hydrogen, which in practical terms makes the stuff less flexible and usually a solid mass at room temperature. For many years, especially in the low-fat crazy days of the 1980s and 90s, we heard that saturated fat is bad for you. All the major medical and government authorities said so. Even the most recent dietary guidelines (2015) from the U.S. government repeat the same mantra — eat less saturated fat. In their sprawling 436 page report, saturated fat is targeted as one of the major concerns for overconsumption. In all, it’s mentioned a total of 256 times — whereby “carbohydrate” is only mentioned 81 times.
Is saturated fat really bad for you? Most likely yes, as compared to diets built around mono- and polyunsaturated fats, such as the Mediterranean diet. And especially when a diet high in saturated fat is also high in carbohydrates (i.e. the typical Western diet). But then again, like many things in the dietary realm, it’s hard to say for absolute certain. After all, some major systematic reviews have seemed to let saturated fat off the hook, such as a 2015 study published in the British Medical Journal. It concluded that saturated fat intake is not associated with all cause mortality, cardiovascular disease, heart disease, ischemic stroke or type 2 diabetes — but also admitted the data is “heterogeneous with methodological limitations,” that is to say, not perfect (20, 21, 22).
But since keto is low in carbs, wouldn’t that make the keto diet an exception to the rule? Maybe! After all, other low carb diets have shown some promise in this area. Just keep in mind that, by their very nature, studies of dietary intake are very problematic. It’s hard to make people eat exactly what you want for very long — and even harder to track “ad lib” dietary intake by relying on surveys and recall. As a result, it may be possible to link certain eating patterns with certain markers of disease — say, LDL cholesterol — but lab values are still far removed from actual disease. It’s all just connecting dots and guesswork at this point, quite honestly (23, 24, 25).
For a perspective on why, in theory anyway, saturated fat may not be as bad as we once thought, check out this video by David Diamond, PhD.
Is coconut oil healthy?
One of the few major sources of saturated fat in the plant world comes from the incredible-edible coconut (the others are palm and palm kernel), which is part of why coconut oil is such a controversial topic. Again, it’s very difficult to draw any hard conclusions from the scientific data, because the studies have a lot of different moving parts.
However, it does appear that coconut oil may indeed be a keto-friendly fat. It’s probably a healthier alternative to animal sources of saturated fat (meat, dairy, etc.) — but likely not as healthy as unsaturated plant oils. For example, a recent review (2016) concluded that coconut oil generally caused less of an increase in total and LDL cholesterol as compared to butter (i.e. it was less bad), while unsaturated plant oils performed the best in these categories. Part of this may be because the composition of coconut oil is different than traditional saturated fats in a few key ways. First, coconut is only 90% saturated fat. And second, about half of its saturated fat is in the form of medium-chain fatty acids — as opposed to animal fats, which are made up almost entirely of long-chain fatty acids (26, 27).
With all that said, it’s probably not advisable to put all your eggs in one basket when it comes to dietary fats, especially if you follow a high-fat diet like keto.
What to know about cheese
Cheese is a macronutrient hybrid food that tends to work well with keto because it’s generally high in fat and protein while being low in carbs. With the exception of cream cheese, cottage cheese and American cheese, which have relatively high carb levels, the vast majority of cheeses contain near or below one gram net carbs per ounce. And to give you an idea, an ounce of cheese is about one slice or two cubes the size of dice.
Parmesan, grated 1 Tbsp / 0.2g
Goat, chevre 1 oz / 0.3g
Bleu cheeses 2 Tbsp / 0.4g
Cheddar 1 oz / 0.4g
Gouda 1 oz / 0.6g
Mozzarella, whole milk 1 oz / 0.6g
Parmesan 1 oz / 0.9g
Swiss 1 oz / 1g
Feta 1 oz / 1.2
What to know about non-starchy vegetables
If you’re trying to keep your life simple while choosing the best foods for a keto diet, feel free to eat the following keto-friendly vegetables as much as you want. The best keto vegetables are all very low in carbs and high in fiber, so a terrific weight-loss food regardless of your diet!
What to know about nuts and seeds
Pardon the pun, but you’d be a nut not to include these nutritional powerhouses in your diet, keto or not. Of course, on keto you’ll have to remain mindful of the carbs they provide also. Fortunately, most nuts and seeds are relatively low-carb foods, not to mention the fact they’re high in fiber, which can be lacking in a keto diet.
They’re also nature’s multivitamin, supplying a rich array of essential micronutrients. For those reasons they definitely make our ketogenic diet foods list. And yes, we realize peanuts are not technically a nut, but they’re included here because they deserve to be a part of your keto diet plan as well.
What to know about fruit
You want to know, can I eat fruit on keto? Well, yes and no. Fruit is amazing stuff — so delicious, so nutritious — yet sadly not the most keto-friendly food out there. Most fruit is sweet for a reason, because it contains the sugar fructose. Just one medium banana, for example, contains about 25-30g carbs, which would obviously break the bank on a classic 20g keto program. A 50g plan, which again is the common cut point between keto and non-keto diets, is a different story though if you choose fruits wisely. Yes, there are some relatively low-carb options.
So don’t get us wrong, a moderate amount of fruit would be a welcomed addition to your keto diet, but you’ve got to be extremely careful and disciplined. Also, if you do choose to include fruit in your keto menu plan, the smartest approach is to eat it along with high fat and/or high protein foods.
Limes 1 fruit / 5g
Blackberries 1 cup / 6g
Raspberries 1 cup / 7g
Clementines 1 fruit / 8g
Asian pears 1 fruit / 9g
Strawberries 1 cup, halves / 9g
Cranberries 1 cup, chopped / 9g
Figs 1 large / 10g
Watermelon 1 cup / 11g
Apricots 1 cup, halves / 12g
Peaches 1 cup slices / 12g
Pomegranates ½ cup arils / 13g
Cantaloupe 1 cup, balls / 13g
Blueberries 1 cup, frozen / 13g
Honeydew 1 cup, diced / 14g
Apricots 1 cup, halves / 14g
Apples, with skin 1 cup / 14g
Grapes 1 cup / 15g
Grapefruit, pink or red or white 1 cup sections, with juice / 16g
Lemon juice 1 cup / 16g
Plums 1 cup, sliced / 17g
Pears 1 cup, sliced / 17g
Oranges 1 cup, sections / 17g
Pears 1 cup, slices / 17g
Blueberries 1 cup / 18g
Sweet cherries 1 cup / 19g
What to know about zero-calorie sweeteners
Very few of us will be satisfied drinking only plain water all day, every day. So certain natural or artificial sweeteners may be useful to encourage proper hydration, which is vitally important when following a high protein diet to maintain healthy kidneys.
Sugar alcohols like sorbitol, xylitol and isomalt contain some net carbs, so it’s best to exclude them from your keto diet plan. However, there is one exception — erythritol — which has zero net carbs and can be used freely.
Sucralose, saccharin and stevia – one packet equals one gram of net carbs. Note that stevia and sucralose must be pure. “Stevia in the Raw,” “Splenda” and other commercial brands contain the carbohydrate maltodextrin and are not recommended. To avoid this, you can buy pure stevia and sucralose in liquid form.
Monk fruit brands often contain sugars such as fructose and dextrose, as well. Choose one such as MonkSweet that contains only erythritol and/or stevia as additives.
Meal planning on a keto diet
What to eat on keto? Let’s face it, keto can be a little complicated, but if you follow some basic rules of thumb you’ll be a keen keto meal planner in no time. Assuming you are not overly restricting your protein intake (all diets except for classic keto), your daily intake by food group will look something like this:
- Meat, seafood, eggs and other high protein foods
- Non-starchy vegetables like cucumbers, peppers, radishes, cauliflower, chard, and zucchini (see below for more vegetables)
- Oils, cream, butter and other concentrated fats
- Nuts and seeds
When planning meals, think about these things, in any particular order.
What is your main protein source?
What is your main fat source?
If your protein also happens to be high in fat (hamburger, bacon, salmon, etc.), or your meal is accompanied by other protein/fat hybrid foods like cheese and nuts, then you only need to use a small amount of added fat such as oil or butter — perhaps one to two tablespoons. If using a leaner protein, then double or triple the amount of added fat to keep the proper macronutrient ratio.
Finally, what is your fiber source? Without fiber in your keto diet, not only may your bowel health suffer but you’ll be more likely to experience negative side effects like high cholesterol. Your fiber could come from vegetables, nuts, seeds, fruit or even a fiber supplement like psyllium husk powder (mixed in plenty of water), which is almost 100 percent fiber and therefore close to zero net carbs.
For snacks, include protein whenever possible and think about creating macronutrient combos. Protein and fat. Protein and carbs. Or all three together, thinking about those hybrid foods like nuts, seeds, and cheese.
Or, if you prefer to have someone just lay it all out for you … check out our 14-day keto meal plan.
Can Keto do that? Potential health benefits of ketogenic diets
Classic ketogenic and other low carbohydrate diets have been shown to have an array of positive effects on health, as well as directly improve many symptoms and markers of disease. The strength of evidence varies quite a lot, however, and there are virtually no reliable studies more than one or two years in duration. So it would be premature to declare keto capable of preventing or curing any disease at this time.
Epilepsy / seizures
This is clearly the keto diet’s wheelhouse. Its very origin story is tied to treating childhood epilepsy, and to this day researchers remain intrigued by the possibilities in this area.
A 2018 Cochrane review examined the most robust trials involving epilepsy and keto diets such as classical, the MCT diet and modified Atkins. Their statistical analysis in comparing one diet against another was limited by the different study designs, and the overall evidence quality ranked as “low” or “very low” — however, some of the results were very promising. Indeed, many subjects who successfully adhered to a keto diet saw greater than 50 percent reduction in seizure frequency, while others were seizure-free during the trial period (28).
Generally, it takes one to three months for a keto diet to have an effect on seizure frequency and the need for antiepileptic drugs (AEDs). Anyone who endeavors to treat seizures through diet modification and wean from AEDs should work hand-in-hand with their doctor and, ideally, a registered dietitian — especially parents of children with epilepsy. There are many factors to consider and close medical monitoring is recommended to ensure safety (29).
Diabetes / blood glucose control
A proper “diabetic diet” is, of course, low in carbohydrates by its very nature — it simply must be so in order to control the disease. But several studies have also demonstrated that even a relatively modest diet and lifestyle changes can help prevent diabetes as well (30–33).
That said, it’s no wonder why those seeking to treat or prevent diabetes have flocked to diets like Atkins, Zone or South Beach over the years. But since we know moderate to high carb reduction works for this purpose, shouldn’t a keto diet for diabetes produce extreme results?
As a matter of fact, yes. Thus far the body of evidence (consisting of well-designed studies with high compliance rates) is quite impressive. Among individuals with diabetes, significant improvements have been demonstrated not only in fasting glucose and hemoglobin A1C levels, but also in LDL cholesterol, HDL cholesterol, total cholesterol and triglycerides. This, in addition to many subjects having experienced weight loss and reduced dependence on insulin and other diabetes medications (34–40).
The tricky part of this research tends to be isolating the effect of carb-restriction versus overall caloric restriction — which, along with weight loss has shown to improve diabetes as well. The good news is that, by reducing carbs and total calories you’re likely to lose weight and have better glycemic control (41).
If you have diabetes, and especially if you take insulin, making a sudden and dramatic change in carbohydrate intake can be dangerous, due to the risk of low blood sugar (hypoglycemia). So before embarking on a keto diet for diabetes, do get your entire healthcare team on board and put strategies in place to maximize your chance for success.
Cardiovascular health / cholesterol
Possibly one of the most controversial areas is the actual or potential effects of a ketogenic diet on markers of cardiovascular disease, in particular, blood lipid profiles (cholesterol, triglycerides, etc.).
Thus far science has done little to put the issue to rest, with results being mixed at best.
According to a comprehensive review published in September 2019, low carbohydrate and very low carbohydrate diets, keto included, had a positive effect on triglycerides and a varied impact LDL cholesterol (i.e., “bad” cholesterol) — that is to say, some saw a decrease in LDL, some saw an increase and many saw no significant change at all. In the final analysis, there was deemed to be no clear advantage to these diets with respect to other cardiometabolic risk markers such as HDL cholesterol (42).
The type of fat you consume on a keto diet most likely makes a difference as well, with evidence showing that plant-based unsaturated fat is superior to saturated fat (48).
If you have a history of cardiovascular/heart disease, or an abnormal blood lipid profile, talk to your doctor about the possible benefits of a ketogenic diet — and if you proceed, set up periodic monitoring of your lab values.
Weight loss and satiety
Chances are, by now you’ve heard from your neighbor, co-worker or brother-in-law that keto works for weight loss. And rest assured, there’s a pile of scientific evidence for this also. Yet there are some reasons to remain skeptical about all these success stories.
Fact one: What few tell you is that most of the weight lost in the initial phase of keto (first week or two) is not fat or lean mass but glycogen (stored sugar) and water. This accounts for four to five pounds (about two kilograms) on average (49–52).
Fact two: Most people cannot stick with a keto diet for more than a couple months, so there are virtually no studies to prove keto diet plans can sustain weight loss in the long term — without other negative health effects.
Fact three: When people quit a keto diet, they gain the weight back — just like they do with other weight-loss diets.
Neurological / brain diseases / behavioral conditions
In total, the number of human trials in these populations is extremely small. Given that compliance and accurate documentation tend to be major problems among keto diet studies, you can only imagine the added complication of subjects with altered mental status and/or behavioral disorders. That’s not to say the research has failed to show any promise at all, however. To the contrary, there are some reasons for optimism — yet the challenge of following a highly restrictive diet will always remain. Not to mention the fact that many sufferers of neuro disease are at high risk of malnutrition, to begin with, and a keto diet may only make matters worse.
While there are several animal studies on ketosis, Parkinson’s disease and Alzheimer’s disease with positive results, to date there are very few human studies. Some improvement in Parkinsonian symptoms and cognitive/memory testing in the case of Alzheimer’s has been reported, but no definitive conclusions drawn. Also, it’s clear that researchers may have some reservations about studying restrictive diets in these populations, given their high risk of underweight and malnutrition as the diseases progress (65).
Only one clinical trial has tested a keto diet, separate from other therapies, on children with Autism spectrum disorder. The trial had 30 subjects and saw a 40% dropout rate. Some improvement in symptoms was reported, the effect being greater on mild symptoms than severe symptoms. Given that children in the autism spectrum are known to have very particular and rigid food preferences, successful long-term use of keto diets in this population seems unlikely (66).
The story of keto trials in relation to anxiety, depression, bipolar, schizophrenia and pathological behavior is very similar. Very few human studies, with no definitive results (67).
In animal models of traumatic brain injury, spinal cord injury and concussion, a ketogenic diet both pre- and post-injury has shown an improvement in structural and functional outcomes. Very few human studies have been conducted to date, although a small pilot study at the University of Alabama at Birmingham has demonstrated improved upper motor function in patients with spinal cord injury on a ketogenic diet. It also showed a reduction of inflammatory markers, which may allude to the mechanism for the diet’s effectiveness (68, 69).
There have been some studies of very low carb diets and cancer. However, given the vast array of cancer types and study designs, it’s not possible to make any inferences about the effectiveness of keto diets on cancer at this time (70–74).
See a brief and entertaining view of what ketosis does to your body in this animated video.
Weighing the risks of going Keto: Potential side effects and safety concerns
The ketogenic diet has been around a long time and is widely believed to be safe, even in young children (if done correctly and monitored closely), yet the old adage of “no pain, no gain” may very well apply. Or perhaps it would be more accurate to say, no pain, no loss — considering the growing reputation of keto for weight loss.
- Acidosis (blood pH too low)
- Carnitine deficiency (not enough of a substance used for fat metabolism)
- Cardiomyopathy (disease of the heart muscle)
- Growth problems in children
- Hyperuricemia (high uric acid)
- Hypercholesterolemia (high cholesterol)
- Hypocalcemia (low calcium)
- Hypomagnesemia (low magnesium)
- Kidney stones or acute kidney injury (AKI)
- Pancreatitis (inflammation of the pancreas)
What to know about the so-called “keto flu”
The pain of keto, so to speak, is usually mild and short-lived in otherwise healthy people — and with most, it starts with the infamous keto flu. So what is the keto flu? Not to worry, it’s not actually influenza, nor is it contagious, however it does share a few symptoms with its namesake virus, such as (87, 88, 89):
- Concentration problems, i.e. “brain fog”
- Electrolyte imbalances (low sodium, potassium, etc.)
- Muscle cramps
Other GI symptoms may present also, including constipation, diarrhea and cramping. Most of these symptoms tend to pass within one to four weeks, but here are some suggestions for how to get through the keto flu with minimal discomfort:
- Get more fiber from keto-friendly vegetables, fruits, nuts and seeds, plus extra from psyllium husk powder if needed.
- Drink more water and other carb-free fluids.
- Add electrolytes such as sodium, potassium and magnesium.
- For sodium, aim for daily intake of about 3-5g, which translates to about 1½-2 teaspoons of table salt added to foods and/or beverages. If you take medicine for high blood pressure, have congestive heart failure (CHF) or have otherwise been advised to avoid salt, consult with your doctor before increasing sodium intake.
- For magnesium, foods such as leafy green vegetables, nuts and seeds are excellent sources. You could also take 400 mg supplemental magnesium daily, preferably with your evening meal as magnesium can help relax your muscles and improve sleep.
- For potassium, whole foods are also the best source including leafy greens, mushrooms, broccoli, brussels sprouts and asparagus.
- Take a daily multivitamin as an insurance policy. For tips on how to choose, along with product ratings, check out this article and video from Consumer Reports. Hint: it doesn’t have to be fancy or expensive!
What to know about bad breath in ketosis
Another unwanted and often unexpected side effect of keto diets is bad breath. Often termed “keto breath,” this phenomenon is one of the classic signs of ketosis caused by your body’s disposal of the ketone body acetone. As we mentioned earlier, you likely recognize acetone as a foul-smelling industrial chemical used for removing paint and nail polish. Combined with other natural breath odors, it’s sometimes described as slightly sweet or “fruity” but regardless it’s not a pleasant aroma to most people. The good news is, like the keto flu, keto breath usually goes away within a couple of weeks as your body adjusts to ketosis.
The best approach to fighting keto breath is to drink plenty of water and use sugar-free products to cover up the smell — like mints, gum, strips or mouthwash. And look on the bright side, if you have keto breath it means you’ve successfully reached ketosis, good job!
When to avoid a keto diet
If you have any of the following health conditions, DO NOT ATTEMPT a keto diet (90):
- Carnitine deficiency (primary)
- Carnitine palmitoyltransferase (CPT) I or II deficiency
- Carnitine translocase deficiency
- β-oxidation defects
- Medium-chain acyl dehydrogenase deficiency (MCAD)
- Long-chain acyl dehydrogenase deficiency (LCAD)
- Short-chain acyl dehydrogenase deficiency (SCAD)
- Long-chain 3-hydroxyacyl-CoA deficiency
- Medium-chain 3-hydroxyacyl-CoA deficiency.
- Pyruvate carboxylase deficiency
Furthermore, if you have any major health condition, but especially the following, take extreme caution and seek medical advice before starting a keto diet:
- Type 1 diabetes; or insulin-dependent type 2 diabetes
- Any major heart problems such as cardiomyopathy, congestive heart failure, atrial fibrillation, etc.
- Chronic kidney disease
- Chronic pancreatitis
- History of gallstones
- History of kidney stones
- Liver diseases such as non-alcoholic fatty liver disease or cirrhosis
- Osteopenia or osteoporosis
Again, there is no cause for alarm here — for the vast majority of people — as dangerous side effects from keto diets are very rare. It does, however, warrant caution and the awareness that not everybody will respond to keto in the same way. The best advice with any major change in your diet is to consult with your doctor and a registered dietitian beforehand and to monitor your health closely afterward via routine checkups and blood work.
How to optimize Keto for your lifestyle and goals
Before jumping straight into a ketogenic diet regimen, it may be helpful to ask yourself some questions such as: Why am I doing this? What do I hope to achieve? Can I picture myself giving up many of the foods I love? And, how long can continue to eat keto?
Keto for weight loss
There’s no doubt a keto diet for weight loss can be very effective. Plus, dropping five pounds in the first week or so of a diet, as is typical with keto, can be a real morale booster (never mind that it’s mostly water weight).
But there are so many different ways to do keto, as we discussed earlier. Which type of keto diet is the best for weight loss? Scientifically speaking, we don’t know. There’s not enough information yet. From a personal standpoint, however, the best keto diet for weight loss is quite simply the one you’re most likely to stick with. If you have a history of trying many different diets for weight loss, only to quit after a short time — then keto may not be right for you.
In terms of expectations, do expect to lose a sizeable chunk of weight in the first few weeks. As you continue, do expect to continue losing weight — up to a few pounds a week — through the first couple months. As with all diets, however, the body tends to adapt and reach equilibrium, causing a plateau in weight loss. Keto is no different, and understand that your ability to lose weight is dependent on many factors including genetics.
Keto and exercise
If you are physically able to exercise, you should — whether you decide to go keto or not. Exercise while in a state of ketosis can be a particular challenge though, especially in the adaptation phase when you may not be feeling quite yourself.
Once your body becomes keto-adapted, exercise should be much better tolerated. If you continue to struggle, however, consider shifting more of your carbohydrate intake to pre-workout meals and snacks. Also, you might take a cyclical or targeted approach to keto and exercise most intensely on those days, or at those times, when you have adequate carbs in your system.
While the research on ketosis and exercise is very limited, studies appear to show that ketosis neither hinders nor enhances strength performance (91–97). In terms of physical endurance, the evidence suggests much the same, although with slightly more concern that ketosis may not be ideal for endurance athletes like cyclists or marathon runners. For the recreational athlete, however, whose goal is to stay fit and/or burn fat keto should be perfectly compatible (98–106).
Entering and maintaining ketosis
Just like there is no “best” type of keto diet, there is not one proven best way to enter a state of ketosis. Again, the best way for you is the one you’re most comfortable with, fits with your lifestyle and produces the fewest side effects. Here are a few methods to consider:
- Ease into ketosis by gradually decreasing your carbohydrate intake — at whatever rate you prefer — until you reach the goal of between 20-50g carbs per day.
- Cut back your carbs all at once.
- Combine either of these two basic approaches with (any or all): fasting days, time-restricted eating or use of MCT oil.
Maintaining ketosis is, of course, dependent on maintaining the diet — again, what your body and mind can tolerate. But once you’ve adapted to ketosis for a period of time (months), it is possible to maintain ketosis while gradually loosening your carb restriction. The amount of carbs at which people “fall out” of ketosis varies widely, so prepare for some trial and error here. It could be very close to 50g a day, or much higher (if you’re lucky).
It’s important to understand that ketosis is not a simple ON/OFF switch. Its levels can be measured via blood, urine or breath testing, measured in mmol/L, with blood tests being the most precise — but obviously harder and more expensive to do yourself at home. There is no universal threshold for ketosis, but greater than 0.2 mmol/L is a generally accepted minimum, while most studies use 0.5 mmol/L as an acceptable lower limit. A level of 3-5 mmol/L is considered to be a high degree of nutritional ketosis — whereas, by comparison, a state of ketoacidosis can push the level upwards of 15 mmol/L. Again this is the difference between someone following a strict keto diet and someone experiencing a true medical emergency.
Is it necessary to check your ketone levels?
Not really. If it helps to reassure or motivate you, by all means, do it. If you have diabetes and have talked to your doctor beforehand as you should, then likely he or she has strongly advised you to do it. Otherwise, the best measure is whatever you hoped to achieve by going keto in the first place. Are you losing weight as expected? Do you feel better? More mental sharpness? And so on. However, if you do decide to monitor ketosis at home, your options are:
- Checking blood ketones — requires a meter, which costs around $40, most of which come with a short supply of test strips, lancets and alcohol wipes for the finger prick. Extra test strips can be expensive at about $1 apiece.
- Checking urine ketones — requires test strips only, which are relatively inexpensive at around $5-10 for a pack of 100. Less accurate than blood testing and you’ll need to color match the strip to approximate ketone levels.
- Checking breath ketones — arguably the easiest method of ketosis monitoring, because it doesn’t require a finger prick or interpretation of the color on a test strip. Meters cost around $50 and do not require strips or filters.
Supplements to your Keto diet
Apart from some of the things previously discussed to help weather the keto flu (electrolytes, etc.), you technically should not require any supplements — if eating from all the various keto-friendly food groups. That said, because this is about “optimizing” your keto diet, we do have some items for your consideration, which may be beneficial.
- Carnitine or Acetyl-L Carnitine – to optimize the fat oxidation or “burning” process, even though only in rare cases will the body run short of carnitine.
- Ketone esters – can be used to mimic or enhance the state of ketosis, often used in animal models of ketosis. There is scant evidence that ketone esters provide any health benefit, however.
- Magnesium – to maintain this important mineral, which has hundreds of different functions in the body.
- Multivitamin with minerals – to provide recommended daily intakes of essential vitamins and minerals, always good to have a safety net with a highly restrictive diet like keto.
- Potassium citrate – to reduce the risk of kidney stones (107).
- Selenium – to maintain this trace mineral key in the immune system, fertility, and cognitive function.
Other supplements may actually cause a problem with keto diets because they tend to lower blood sugar and therefore increase the risk of hypoglycemia:
- Salacia reticulata
*Amounts provided in multivitamins up to 100% Daily Value are acceptable.
Traveling on a Keto diet
Restaurants are a nutritional minefield regardless of your diet, but can pose even more of a problem on keto. Here are some tips for traveling, and eating out, on a keto diet:
- Be prepared. Know your keto-friendly foods like the back of your hand before you venture out.
- Plan ahead. Pack good keto snacks like the ones featured in our 14-day keto meal plan.
- Map your course. Look for the places on your route most likely to accommodate your keto needs. In general, independent restaurants are more open to special orders than big chains.
- Make your wishes known. If servers and chefs know up front you’re on a keto diet, they’ll be more likely to work with you — versus just thinking you’re a picky eater!
- Request substitutions. Most dishes will not be keto, as is, but many will be close. Sometimes it’s just a simple matter of leaving off the bread or swapping out potatoes for a non-starchy vegetable.
- Request extra fat. If you feel like your macros are malproportioned (too much protein and/or carbs, not enough fat), then request a “shot” of oil. Preferably olive oil, but in a pinch any vegetable oil will do.
- Accept defeat gracefully. Sometimes your friends may insist on going out for pizza. And let’s face it, pizza can be so magical to the taste buds. So eat pizza — and don’t pout about it — just get back onto your keto horse afterward and ride on.
Frequently asked questions (FAQs)
Q: Will I get low blood sugar if I follow a ketogenic diet? Can’t this be dangerous?
A: Yes, low blood sugar (hypoglycemia) can be extremely dangerous or even deadly — but no, unless you are taking insulin for diabetes, it’s highly unlikely this will be a problem. Your body is able to make enough glucose from proteins (glucogenic amino acids) and fats (glycerol, which is part of a triglyceride) in order to keep circulating blood glucose within normal limits.
Q: What is considered a “low carb” diet?
A: Generally, less than 80g carbohydrates daily may be considered “low carb,” while less than 50g is “very low carb” and the 20g range is strictly keto.
Q: Can you eat cheese on keto?
A: Yes, cheese is mostly protein and fat, which are keto-friendly. But cheese does contain small amounts of carbs — some varieties more than others — so you may not be able to eat large amounts of cheese and maintain ketosis.
Q: Can you eat fruit on keto?
A: Yes, but in moderation and paying close attention to whether the fruit is keto-friendly or not.
Q: How long is it safe to be in ketosis?
A: Theoretically, it’s safe for a lifetime, as all bodily functions can be performed in a state of ketosis. However, whether a keto diet helps you live longer or not has yet to be proven.
Q: How can you tell if you’re in ketosis?
A: Apart from checking your ketones (from blood, breath or urine), there’s no way to know precisely what level of ketosis you may be experiencing. However, there are some physical signs of ketosis including “keto breath” and “keto flu” both of which are explained in this article.
Q: What is the best keto diet for beginners?
A: Any type of keto diet that fits with your eating preferences, lifestyle and goals is perfectly fine. But if you’re concerned about being able to restrict carbs to a great degree all the time, then perhaps a liberalized, cyclic or targeted keto diet may be right for you.
Q: Is the keto diet healthy?
A: Strictly speaking, the jury is still out on this question. Though it’s safe to say that the healthiest keto diet includes the widest variety of whole foods, such as vegetables, nuts, and seeds while utilizing lots of plant-based unsaturated fats (olive, flaxseed, avocado, etc.) and lean proteins (fish, poultry, eggs, etc.).
Q: How long does keto flu last?
A: On average 1-4 weeks. It depends on your body’s timeline for adjusting to ketosis, and perhaps how diligently you maintain proper hydration, electrolytes, and other key nutrients. Also, gradually decreasing your carb intake over a few weeks may help you avoid severe keto flu symptoms such as fatigue, nausea and brain fog.