Everything you need to know about this popular low-carb diet

How to Get Started With the Ketogenic Diet

Is the Keto diet right for you? If so, here’s a complete guide to getting started.

John Fawkes
May 10 · 27 min read

I was a latecomer to the ketogenic diet. I had first heard about it years ago when Tim Ferriss briefly mentioned his experience with the cyclical ketogenic diet. Since then, as the diet grew in popularity, I read a growing number of articles about the ultra-high-fat, low-carb ketogenic diet.

In short, the ketogenic diet entails eating less than 50 grams—and usually less than 30 grams—of net carbohydrates per day. It’s important to note that net carbohydrates are carbohydrates minus fiber; these are the only carbohydrates your body burns for energy. Protein is consumed at moderate levels on the ketogenic diet, so around 80% of your total caloric intake comes from fat.

Extreme? Hell yes. But is it effective? Often (but not always), it is. Sometimes astoundingly so.

Bodybuilders and fitness models love the ketogenic diet for its ability to facilitate rapid fat loss while sparing muscle tissue.

Athletes love the keto diet because there is evidence that a ketogenic diet improves endurance compared to more conventional, moderate-to-high-carb diets.

Paleo dieters love the ketogenic diet because it virtually eliminates many foods that cavemen supposedly didn’t eat, like grains and legumes, which can irritate the gut and cause digestive and autoimmune issues for some people.

Minimalists love the diet because it’s simple. The ketogenic diet severely restricts what types of foods you can eat, so it’s easy to end up eating the same few things over and over.

People who struggle to lose weight are drawn to this diet because it makes it easy to eat less. Ketosis, a metabolic state that the body enters when eating very few carbohydrates, suppresses your appetite. I’ll get into more in a bit.

And most recently, Silicon Valley techies and productivity gurus have begun to embrace the ketogenic diet for its supposed mental benefits — improvements in energy level, wakefulness, and mental sharpness.

Now, you might ask, how could eating a nearly all-fat diet effect such radical improvements on the body? The ketogenic diet works by putting the body into an altered metabolic state called ketosis. To understand the ketogenic diet, you first need to understand what ketosis is and how it’s induced.


A Brief Primer on Ketosis

The body has many different metabolic pathways that are used to produce energy, but some get used more than others. Normally, most of your body’s energy comes from glucose, the simplest and most common form of sugar.

Much of the sugar that we consume is in the form of pure glucose, but other carbohydrates can be broken down or processed into glucose. When the body runs low on glucose, it can also transform fat and protein into glucose through a group of reactions collectively known as gluconeogenesis.

Aside from glucose, the body can run on other energy sources, including ketones and free fatty acids. However, since glucose is the preferred fuel source, those other energy sources only start to be used in large quantities when the body’s glucose stores get depleted.

Depletion of the body’s glucose stores is usually the result of fasting, eating a very low-carb diet, exercise, or some combination of the three. In some cases, it can also result from metabolic disorders, like Type 1 diabetes.

Near-total depletion of the body’s glucose stores normally takes around 24–36 hours, although this process can be sped up through exercise. As your body’s glucose reserves get depleted, it begins to compensate by burning more free fatty acids for energy.

Initially, the body relies more on free fatty acids than ketones. However, many cells in the body are unable to directly utilize free fatty acids. The brain, in particular, can’t use them because free fatty acids can’t cross the blood-brain barrier. Therefore, as your glucose reserves continue to get depleted, the liver starts to process more and more of those fatty acids into ketone bodies.

Once your glucose stores are almost completely depleted, the body enters a state called ketosis, in which the majority of its energy needs are met through ketone bodies—often referred to as ketones for short.

It’s important to understand that ketosis is not an on/off switch, but rather a gradual increase in your body’s production of ketone bodies. Nutritional ketosis is defined as a blood ketone body concentration of .5 to 3 millimoles per liter, abbreviated as mmol/L.

The body always produces some amount of ketones, even when on a high-carb diet. A ketone concentration of .2-.5 mmol/L is sometimes referred to as mild ketosis, but at that point, the body is still not running primarily on ketones. Post-exercise, your ketone levels can briefly go as high as 3.5 mmol/L. Higher numbers, around 4–10 mmol/L, are typically only seen in starvation conditions.

Even higher concentrations, around 10–25 mmol/L, represent a dangerous condition called ketoacidosis which normally only occurs in diabetics, alcoholics, and people who are starving to death. Note that some people claim that ketosis is inherently dangerous—these people are confusing ketosis with ketoacidosis.

Ketones are a class of three chemicals: acetone, acetoacetate, and beta-hydroxybutyrate. In mild stages of ketosis, acetoacetate is the primary ketone produced by the body. In deeper stages, beta-hydroxybutyrate starts to dominate as the body’s largest energy source. Acetone is produced as a breakdown product of both of the other ketone bodies. (Yes, I’m talking about the same compound “acetone” that’s in nail polish remover and paint thinner. Yes, your body can burn that for energy. No, that doesn’t mean it’s safe to drink paint thinner. Please don’t!)

Once you’re in a state of ketosis, your body will start to excrete small amounts of excess ketones in the breath and urine. Ketones in the urine can be detected using special ketone-measuring strips—discussed below—which are used to measure whether a person is in ketosis. Ketones on the breath, particularly acetone, may give your breath a slightly sweet and fruity odor.

Different tissues in your body have different energy preferences. Most are flexible: they can run on glucose, ketones, or free fatty acids. Some, however, seem to run better on some energy substrates than others — as an example, there’s evidence that some (not all) parts of the brain run better on ketones, while fast-twitch muscle fibers run better on glucose.

Some organs and types of cells are unable to utilize ketones. The liver, for instance, is unable to directly utilize ketones for energy, although it can process a small amount of acetone into the energy substrate pyruvate, which is also created as a breakdown product of glycolysis. Some tissues, including certain parts of the brain, need glucose specifically. Thus, even in a state of deep ketosis, the body will still produce some glucose via gluconeogenesis — the breakdown of fat and protein.

Although mild ketosis can be reached within 24 hours of cutting out carbohydrates, nutritional ketosis typically takes 3–4 days to get to—though again, this process can be sped up via exercise. But ketosis only means that the body is producing ketones. Your body still may need a while to adapt to using ketones for energy.

Keto-adaptation is the process by which your body’s cells adapt to run on ketones instead of glucose. After you first enter ketosis, there is a period in which the body gradually ramps up the metabolic pathways used for burning ketones, as well as disposing of the waste products. To be clear, your body is able to utilize ketones right from the start—you won’t starve on a ketogenic diet—but your energy level may be lower than normal for a while.

The entire process of keto-adaptation normally takes 2–4 weeks. The first few days of this process are sometimes unpleasant. If your body is unused to using ketone bodies for energy, you may have an extended period called the keto flu, in which you experience symptoms similar to a blood sugar crash or mild head flu. Ways of minimizing this will be discussed later.

Once in ketosis, you need to continue eating very few carbohydrates—most typically less than 50 grams a day—to stay in that state. If you binge on carbs, you will leave ketosis. This doesn’t undo all of the progress you made towards becoming keto-adapted, but you may experience the keto flu again—albeit likely a milder version of it—as you re-enter ketosis.

This is one of the biggest difficulties with the ketogenic diet: the consequences for breaking it can be unpleasant. On the plus side, it provides a powerful incentive not to break the diet. That’s great because there are several compelling benefits for following a ketogenic diet.


The Benefits of a Ketogenic Diet

Reduced hunger and enhanced fat loss on the ketogenic diet

The weight of evidence suggests that ketogenic diets produce superior fat loss results compared to non-ketogenic diets. Many keto advocates are confused about the mechanism behind this, however.

It has been widely alleged—mainly by bloggers and other non-academic sources—that a ketogenic diet makes it possible to lose weight even without eating fewer calories than you burn. This appears to be incorrect. Ketogenic diets don’t produce greater fat loss than high-carb diets when caloric intake is equal, although they do provide greater improvements in glycemic control.

Instead, the ketogenic diet seems to lead to weight loss primarily by making people eat less. A ketogenic diet can strongly suppress one’s appetite, to the point where many people don’t feel hungry at all even while losing substantial amounts of weight. The exact reasons for this are unclear, but what is known is that the appetite suppression effect comes on gradually. It can take up to 3 weeks for your appetite to become fully suppressed on a ketogenic diet, suggesting that it results from keto-adaptation, and not merely by being in ketosis.

Interestingly, being in ketosis for a long time reduces conversion of the thyroid hormone T4 to T3, the more active form. This would theoretically be expected to reduce energy expenditure, but that doesn’t seem to happen. Energy expenditure stays about the same as normal on a ketogenic diet.

The ketogenic diet may also help to preserve muscle mass while losing weight. In the long run, anyway — this may only hold true after you’ve become keto-adapted, which again, takes up to 4 weeks.

So in short, being on a ketogenic diet helps you lose weight because you eat less while burning the same number of calories as usual.

The cognitive benefits of ketosis

Many people find that after they get past the initial keto flu and become fully keto-adapted, they experience improvements in various aspects of mental functioning. Among other things, this includes mood, the ability to think clearly and stay focused, energy level, and subjective well-being.

Studies usually find that ketogenic diets improve mental functioning more so than low-fat diets.[2] Not all studies reach this conclusion, but at worst ketogenic diets seem to be equivalent to low-fat diets in their effects on mental functioning.

The reasons for improved mental functioning on the ketogenic diet are unclear. It could be because, as mentioned, parts of the brain seem to run better on ketones. It could also be because the ketogenic diet leads to steadier energy levels, because eating more fat increases and normalizes the production of steroid hormones like testosterone, or even because the ketogenic diet eliminates chemicals like gluten and lectins, which many people have bad reactions to.

As a side note on the mental effects of ketosis, the ketogenic diet is commonly prescribed as a treatment for epilepsy. It has been used for this purpose since the 1920s, with patients frequently experiencing more than a 50% reduction in seizure frequency.

There is also emerging evidence that ketogenic diets can improve behavior management and quality of life in children with autism.

Protection against neurodegenerative disease

A growing body of evidence suggests that the ketogenic diet can protect against a variety of neurodegenerative diseases. Specifically:

A pilot study suggested that a ketogenic diet may have therapeutic effects in treating Parkinson’s disease.

A ketogenic diet can lessen the occurrence and severity of migraines.

One study found that a ketogenic diet may prevent traumatic brain injuries from worsening.

Most tellingly, in elderly adults at risk of Alzheimer’s, a ketogenic diet improved overall cognitive functioning. Memory performance was also positively correlated with blood ketone levels, strongly suggesting that it was ketosis that caused the benefits, rather than something else like eliminating gluten or processed sugar.

Ketogenic diets as a treatment for diabetes

Ketogenic diets improve glucose metabolism and insulin sensitivity, making them an effective treatment for type 2 diabetes.

In fact, low-carbohydrate diets in general — even non-ketogenic ones — improve diabetes symptoms and reduce the need for insulin injections, even independent of weight loss.

This is not true of everyone, however. The ketogenic diet seems to benefit a sizable majority of people with type 2 diabetes, but some individuals are carb hyper-responders and will do better on a high-carb diet.

Improvements in cardiovascular health

Most people who try a ketogenic diet will see an increase in HDL cholesterol, along with reductions in both LDL cholesterol and triglycerides. This occurs independent of weight loss — a ketogenic diet can improve your health even if you’re not overweight.

However, this assumes you’re eating a balanced fatty acid profile — one with a fairly even mix of saturated, monounsaturated, and polyunsaturated fats. If your diet is skewed too much towards saturated fats, the effects on your lipid profile are more likely to be negative.

Reduced Inflammation and Cancer Risk

The ketogenic diet has been shown to reduce overall levels of inflammation in a wide variety of study populations, including epilepsy patients, obese adults, and endurance athletes.

Ketosis has been shown to reduce the incidence of cancer in humans, as well as in a variety of animal species. In fact, it seems to be more protective against cancer than intermittent fasting, another dietary strategy commonly touted as having anti-cancer benefits.

This is unsurprising, as inflammation is one of the biggest risk factors for cancer. Over time, chronic inflammation can damage your DNA, causing cells to turn cancerous- so by reducing inflammation, ketosis protects your DNA.


The Downsides of a Ketogenic Diet

Diet adherence

As you could probably guess, the ketogenic diet is one of the harder diets to adhere to. However, it’s not as hard as you might think. In one study, 53% of subjects on the Atkins diet were able to adhere to their diets and complete the study, compared to 65% of subjects on each of the Zone and Weight Watchers diets. Note that Atkins, at least the first stage, is one of the more extreme forms of the ketogenic diet, as it has rules and restrictions beyond what is necessary to stay in ketosis.

All things considered, a well-executed ketogenic diet is only slightly harder to adhere to than other diets. It helps if you cook most of your meals at home though, and you can learn to make ketogenic versions of popular high-carb foods. If you eat out a lot, the ketogenic diet gets harder, as you have to be careful about where and what you eat, and diligently check nutrition labels before ordering food.

Athletic performance on the ketogenic diet

Perhaps the most controversial aspect of the ketogenic diet is its effect on athletic performance: strength, power, speed, and endurance. The evidence here is quite mixed.

In theory, because endurance activities like distance running deplete your glycogen (carbohydrate) stores and have to be fueled primarily by fat, you would expect a ketogenic diet to make you better at them. Some studies have indeed found that the ketogenic diet improves performance in endurance athletes.

Other studies have produced diverging results, with one suggesting that a low-carb but not ketogenic diet was better for endurance. Other studies have found ketogenic diets to be no better or worse than conventional diets for endurance.

The ketogenic diet appears to have no impact on strength performance. In both gymnasts and Tae Kwon Do competitors, going keto did not impact strength even when the athletes trained several hours a day. This is likely because maximal strength—as in lifting a heavy barbell for less than five repetitions—is fueled mostly by ATP stored in the muscle tissue, and thus not strongly impacted by the mix of carbohydrates vs fats in one’s diet.

If “endurance” consists of over an hour of continuous activity, and “strength” consists of very short bursts of activity under 10 seconds long, what about the area in between?

Exercise with durations in this middle range is normally fueled primarily by glucose, so this is where you would expect to see the ketogenic diet do worse. And indeed, this is the area where the ketogenic diet clearly underperforms high-carb diets — ketogenic dieters do worse on anaerobic (that is, a sprinting pace) cycling tests.

In summary, the ketogenic diet may be slightly better or slightly worse for exercise greater than an hour in duration. It makes no difference either way for very short bursts of exercise, under 10 seconds long, provided you take long rests (several minutes) in between bouts of exercise to replenish your muscles’ ATP stores. It definitely reduces performance for exercise in the intermediate range, like short-distance running and most team sports.

Insomnia during ketosis

Some people experience onset insomnia (difficulty getting to sleep) during ketosis. This occurs because ingesting carbohydrates aids in melatonin production and speeds sleep onset.

This is most likely to be an issue in people who already experience insomnia. It can be mitigated, if not entirely prevented, by consuming most of your daily net carbohydrate allotment with dinner. If you do suffer from insomnia to any degree, you should definitely make an effort to treat it—read my guide to fixing insomnia here.


Who Should Do Keto?

The following is my own opinion, based on a combination of research and personal experience.

Anyone can follow the ketogenic diet, but there are a few things to consider in assessing whether you’re likely to have an easy time following it.

Note that this is all about how likely you are to be able to easily follow the diet, not how likely it is to benefit you if you do follow it.

You need to be able to eat enough

The ketogenic diet suppresses your appetite, sometimes powerfully so. When I tried the ketogenic diet, I found myself unable to eat enough. By my calculations, I typically ate between 1500 and 2000 calories a day, while burning closer to 3000. That isn’t enough (for me, at least).

The thing is, I’ve never been overweight, and probably never will be. I was actually underweight as a kid, and when I don’t take care of myself, I tend to under-eat and lose weight. That, of course, is the opposite problem from what most people have.

So my first recommendation would be: the ketogenic diet is likely to work best if you tend to overeat, and if you’ve been overweight in the past, or know you’ll become overweight if you don’t watch your diet.

That describes most people, but if you’re a naturally skinny person like me, you’re likely to either under-eat or resort to making your calorie targets by drinking oil and eating ungodly amounts of cheese.

Consider athletic performance

As mentioned earlier, the ketogenic diet has mixed effects on athletic performance. It doesn’t make much difference either way for powerlifters and very short-distance sprinters, and may or may not help marathon runners. It will probably hurt you if you play soccer, basketball, tennis, or any other sport involving bouts of activity several minutes long.

You need to consider what your favorite physical activities are, and how the diet is likely to impact them. And of course, you need to ask yourself how high of a priority athletic performance is for you.

You need to be disciplined

The ketogenic diet requires more discipline than most diets. That’s not just because it’s harder to follow, but also because it has unusually harsh consequences for breaking the diet.

With most diets, a short binge just makes you feel kind of crappy for a few hours and maybe makes you gain a quarter pound. On the ketogenic diet, it knocks you out of ketosis, and you might suffer the keto flu for a day or more before getting back into ketosis.

This does have an upside, in that it can motivate you to stick to the diet. Still, you should consider how good you are at sticking to diets before going keto.

You need to know what you’re eating

This is a more practical consideration, but since you’re keeping your net carbohydrate intake below 50 grams a day, you need to know which foods have hidden carbohydrates. This has several corollaries.

First, you should be knowledgeable about food in general. If you’re unsure about the carb content of a food, look it up in the SELF Nutrition Database.

Second, you want to be cooking at home as much as possible so you can control what you eat. As mentioned earlier, this is a hard diet to follow when you eat out a lot.

Third, you want most of what you eat to have available nutrition information. That’s relatively easy in California, where all packaged food has nutrition labels and fast food chains have to post nutrition info. It’s a lot harder in countries without strict nutrition labeling laws.


How to Get Keto-Adapted as Quickly as Possible

There are several approaches to getting onto the ketogenic diet. The initial adaptation phase can be short and painful, or long and still fairly painful. I’m firmly of the opinion that it’s better to get over the hump as fast as possible. That said, there are a couple of things you can do to get a head start on keto-adaptation before you actually go into ketosis.

The following protocol is the one used by Johns Hopkins hospital, but with an additional (optional, but recommended) pre-adaptation phase added beforehand.

Phase 1: Pre-Adaptation

Duration: 2–4 weeks

Before starting the ketogenic diet, you can prepare yourself for it a couple of different ways.

First, you can start the process of keto-adaptation by providing your body with ketones, despite not being in ketosis. How do you do that? Two ways.

First, by consuming the aforementioned MCT oil. The dosage here is about 40–80 grams a day of coconut oil.

Second, you can consume ketones directly, in powdered form. There are a lot of fancy, overpriced ketone supplements, but in my opinion, they don’t justify their cost. I prefer to buy ketone powder in cheap, bulk powder form.

The other thing you can do is go on a reduced-carb, but not ketogenic diet by eating around 100 or so grams of carbs a day. This in and of itself doesn’t do much to increase ketone production; what it does do is get you used to eating low-carb foods.

After 2–4 weeks of this, move on to phase 2.

Phase 2: Inducing Ketosis

Duration: 4 days

Continue the phase 1 diet through dinner of the last day before starting keto- phase 2 should be begun in the morning.

On day 1, skip breakfast and lunch, fasting all day until dinner. For dinner, consume a small high-fat, zero-carb meal. This meal should be about one-third the size of a normal meal, so around 200–300 calories for most people. That means it should have about 10–15 grams of protein and 15–30 grams of fat. (Johns Hopkins uses non-alcoholic eggnog for this purpose.)

On the second day, consume a similar meal for breakfast and lunch, but for dinner, double the size to two-thirds the size of a normal meal.

On the third day, consume these two-thirds sized meals for breakfast and lunch, and consume a full-sized — but still carb-free — meal for dinner.

On the fourth day, all of your meals can full full-sized, and you can start to include non-starchy vegetables and low-sugar fruits.

This is the point at which patients at Johns Hopkins are normally discharged from the hospital. By the end of this day at the latest, you should be about as deep into ketosis as you’re going to get.

I have four pieces of advice for helping you get through this.

  • First, don’t “work out,” but do a lot of walking, particularly on day one. This will burn through your glucose stores so you get into ketosis faster. If you reach a point where you feel like you don’t have the energy to walk anymore — your legs feel like they’re not sore but simply “out of fuel” — that’s a good sign. It means you’ve depleted the glycogen in your legs.
  • Second, keep consuming ketone powder during this phase.
  • Third, since you’re not consuming fruits and vegetables for the first three days, you’ll want to get vitamins and minerals from some other source. A multivitamin isn’t a terrible idea, but a serving of greens powder with dinner will more closely mimic what you’d get from actual produce.
  • Fourth, get your electrolytes. Put both table salt and potassium salt on your meals, or drink a sugar-free sports beverage every day to avoid electrolyte depletion.

Phase 3: Keto-Adaptation

Duration: 2–4 weeks

Once you’re in ketosis, you still need a few weeks to fully adapt to the diet. During this time, you should still keep carbs low—around 30 grams on days when you work out, and 20 grams on days when you don’t. You can start working out now, but your energy level is likely to be a little lower at first. That’s okay; it will come back over time.

At this stage, around 75–80% of your caloric intake should come from fat, with 20–30% each coming from saturated, monounsaturated and polyunsaturated fats. 15–20% of your calories should come from protein, while less than 5% should come from carbs.

There’s no need to keep consuming the ketone powder at this point- it isn’t giving you anything your body isn’t producing plenty of once you’re in ketosis.


What to Eat Once You’re on the Ketogenic Diet

Added fats and oils

You’ll need to go out of your way to add fat to your diet. To keep a balance of the three types of fat, look to the following:

  • Saturated fat: Mainly coconut oil, but also butter and palm kernel oil.
  • Monounsaturated fat: Olive oil and canola oil.
  • Polyunsaturated fat: Flax, corn, soybean and sunflower oil.

Tea and coffee

These tend to be staple beverages on the ketogenic diet, particularly because you can add some coconut oil to them to aid in ketone production. For sweeteners, you can use stevia and cinnamon.

Dairy

Milk needs to be avoided due to its sugar content. However, cheese, butter, cream, and sugar-free yogurt all have a place on this diet. Be wary of overdoing it, though—many keto dieters end up eating insane amounts of cheese.

Nuts and nut butters

Peanuts are easily the most popular nut in America, but try to branch out by eating other nuts, particularly almonds, cashews, and walnuts. Also, peanut, almond and cashew butter are healthy ways to add more fats and more flavors to your diet.

As with tea and coffee, you can flavor nut butters by adding artificial sweeteners and cinnamon. They also make great additions to low-carb bread substitutes.

Low-carb food substitutes

There are a surprising number of low-carb substitutes for foods that are normally extremely carb-heavy. The downside is that you usually have to cook them yourself. The upside is that done right, they’re delicious. Just a few examples:

It takes a little practice, but before long you can make ketogenic recipes that taste just as good as the high-carb foods you’re used to.

Meat, fish and eggs

The ketogenic diet tends to be fairly meat-heavy. Many people go out of their way to eat fatty meats like bacon and hamburger. However, if you’re adding MCT oil to your diet, you shouldn’t really be going out of your way to eat more saturated fats.

Fish, including shellfish, are a great addition to the ketogenic diet because they have mostly unsaturated fat. Salmon, in particular, is a great way to round out your fatty acid intake without slathering everything in olive oil.

Eggs should also be included. While they do have a fair amount of saturated fat, the yolk has a lot of B vitamins. What about cholesterol? Your body uses cholesterol to make steroid hormones like testosterone and estrogen — and it turns out that eating cholesterol doesn’t usually raise your blood cholesterol levels.

Non-starchy vegetables

Basically, you can eat every vegetable except tubers like yams, potatoes, and sweet potatoes.

Eat a variety of vegetables in a variety of colors: peas, carrots, green beans, celery, cauliflower, broccoli, squash, eggplant, peppers, spinach — the list goes on.

Eat at least five servings of vegetables a day, but more is even better. You can also lightly fry them in oil to help you eat more fat.

Low-sugar fruits

Most fruits are so high in sugar that they need to be avoided on the ketogenic diet, so you need to know which ones are okay.

Avocados and tomatoes are fine, as they’re not significantly sugary at all, and loaded with nutrients. You can eat as many of them as you want.

Berries are the main fruit consumed on the keto diet, as they tend to be very low in sugar despite tasting very sweet and tart. Strawberries, raspberries, and blackberries are best here. Blueberries are a little higher in sugar and should only be consumed on occasion.

Other than that, cantaloupes, plums, lemons, limes, and coconuts are fine in small amounts. Other fruits are too sugary, and should rarely be eaten on a ketogenic diet.

Dietary supplements

There are three dietary supplements that I would recommend for the ketogenic diet in particular.

  • First, raspberry ketones should be consumed during the pre-adaptation and induction phases. The ideal dose here is about ten grams, 3–5 times a day.
  • Second, a greens powder can effectively give you extra servings of fruits and vegetables, without the carbs. You should still eat actual fruits and vegetables, but a serving a day of greens powder is a good way to cover for what I consider the biggest weakness of the ketogenic diet.
  • Third, a fiber supplement taken once or twice a day, with meals, can go a long way towards ensuring that you get the fiber you need. Again, it’s no supplement for eating real food, but it helps. You should consume around 30–50 grams of fiber a day; getting 5–10 grams a day from a supplement makes this goal easier to reach. Make sure your fiber supplement is sugar-free, especially if it’s in gummy form.

Knowing what to eat is important—but read on for mistakes to avoid.


The Top Mistakes People Make When Starting Keto

Here’s a brief overview of what not to do. These are common mistakes you should avoid making yourself.

Not eating enough protein

Because protein can be converted into glucose in your body, eating too much of it can knock you out of ketosis, the same as eating too many carbohydrates. Many people, upon learning this, mistakenly get the idea that less protein is better. It isn’t.

Your body needs protein to serve as the building blocks for most of your bodily tissues, especially your muscles. Protein used for this purpose will not be converted into glucose. Only protein consumed in excess of what your body needs will be turned into glucose.

So how much protein does your body need? A good guideline is either .8 to 1 gram of protein per pound of lean body weight—that is, body weight that isn’t fat—or 20% of your total calorie intake — whichever is less. That assumes you’re physically active, including at least some weight training. If you’re sedentary, go with .6 grams per pound of lean body weight or 20% of caloric intake, whichever is less.

Remember that protein and carbohydrates have four calories per gram, while fat has nine calories per gram. In other words, you should be eating at least two grams of fat per gram of protein.

Easing into ketosis gradually

This is the mistake I made the first two times I tried this diet: trying to gently slide into ketosis by gradually reducing my carbohydrate intake. This sounds like it would be the easiest way to start the diet; the problem is, it tends to draw out the initial adaptation period, and thus extend the time period in which you suffer from the keto flu.

You can, and probably should, gradually reduce your carbohydrate intake into you’re almost in ketosis. But once your carbohydrate intake is beneath 100 grams a day, it’s better to just take the plunge and cut out all carbs for a few days. This isn’t fun, but it gets the hard part over with quickly.

Cycling in and out of ketosis too often

To adapt to the ketogenic diet, you need to stay in a state of deep ketosis for at least a month. After that, you won’t lose your keto-adaptation immediately if you leave ketosis, but you will gradually de-adapt if you stay out of ketosis for a long time.

Added to that, every time you leave and re-enter ketosis, you’re likely to go through the keto flu again, which isn’t fun.

All things considered, it’s best not to take very many breaks from this diet. You can certainly go off it for a while, but it’s better to take occasional longer breaks rather than frequent short ones. Once you’re on the ketogenic diet, you should be staying on it for at least a month, and ideally several months.

Not eating fruits and vegetables

People need a variety of nutrient, including vitamins, minerals, and fiber. Nothing about the ketogenic diet changes that. However, people on ketogenic diets frequently under-eat plant foods for fear of eating too many carbohydrates, leading to nutrient deficiencies.

First off, remember that you want to stay under 50 grams a day—probably even under 30 grams a day—of net carbohydrates, not total carbohydrates. Fiber doesn’t count towards that total.

Ideally, you’d want to eat about five servings of vegetables and four servings of fruit per day. A serving of either is about 75–100 grams, or half a cup.

Non-starchy vegetables like broccoli, carrots, spinach, celery and squash are almost entirely devoid of net carbs, so eat those to your heart’s content. Non-sugary fruits like tomatoes and avocados are also devoid of net carbs. And you can eat some low-sugar fruits — berries in particular. Just avoid more carb-heavy fruits like peaches and bananas.

Minimizing carbohydrate intake

This one will surprise most people. Yes, you need to keep your carbohydrate intake very low on the ketogenic diet. However, lower isn’t necessarily better.

Remember that going as deep into ketosis as possible isn’t the goal. The goal is weight loss, productivity, athletic performance, avoiding diabetes, or whatever your motive was for starting the diet. Ketosis is just a means to an end.

Minimizing carbohydrates is counterproductive both because it forces you to avoid the aforementioned fruits and vegetables, and because having some carbohydrates helps to fuel physical activity and curb hunger. Your goal should, in fact, be to eat as many carbohydrates as you can while still consistently staying in ketosis.

For most people, that will mean somewhere around 30 grams of net carbs per day, and maybe closer to 50 on days when you do a hard workout. The vast majority of people should not be eating fewer than 20 grams of net carbs per day, except maybe during the first few days as they enter ketosis.

Not including medium-chain triglycerides

Medium-chain triglycerides, or MCT oils, are a type of fat that is known to be particularly ketogenic. In layman’s terms, consuming MCT will cause your body to produce more ketones, and less glucose, than consuming even other types of fat.

Because they are so ketogenic, medium-chain triglycerides are often processed into ketones even on an otherwise non-ketogenic diet. Consuming large amounts of MCT allows you to stay in ketosis while consuming more protein and carbohydrates than you would otherwise be able to. This is beneficial both because more protein, fruits and vegetables are good for you, and because allowing more variety in your diet makes the diet easier to stick to. As an added bonus, MCT oils enhance fat loss.

The best source of MCT is coconut oil, which is 60% medium-chain triglycerides. Palm kernel oil is a close second at 50%, while dairy fats are about 10% MCT. However, only coconut oil contains all four sub-types of MCT fats, which makes it the optimal choice.

Not eating a variety of fats

Some versions of the ketogenic diet get as much as 70% of their calories from MCT oil. This is not a great idea, because MCT oil is saturated fat, and eating so much saturated fat — without balancing it out with unsaturated fats — risks raising your LDL cholesterol and triglyceride levels while lowering HDL cholesterol.

You want a balance of saturated, monounsaturated, and polyunsaturated fats in your diet. That means no more than 30% of your total calories should come from saturated fat, and probably no more than 20% should come from MCT oils — there are other types of saturated fat you’ll end up consuming too, like meat and cheese.

To balance out your saturated fat intake, consume unsaturated fat sources such as fish, avocados, nuts, and olive and vegetable oils.

Relying on ketone test strips

Ketone test strips, or ketostix, are strips which change color when exposed to ketones. You’re supposed to pee on them to measure the amount of ketones in your urine and see how deep into ketosis you are. This is counterproductive for several reasons.

First, as mentioned, getting as deep into ketosis as possible isn’t the goal. It’s a means to an end.

Second, the amount of ketones in your urine is only weakly correlated with the amount in your blood. Sometimes your body will stop excreting ketones into your urine altogether, even when you’re deep into ketosis, which can make it look like you’ve left ketosis.

Third, ketone strips only measure one type of ketone: acetoacetate. But beta-hydroxybutyrate is usually the main ketone the body produces. If you have no acetoacetate in your urine, you may still have a lot of BHB, it just won’t be detected.

Ketone breathalyzers exist, and are more reliable than ketone strips, but also far more expensive. Blood tests are better still, but even more expensive and invasive, and can’t be done often. And the three don’t correlate well with each other.

But most importantly, none of it is all that important. You know you’re in ketosis if you've followed the diet for over a week straight. How deep into ketosis doesn’t matter. What matters is how you feel, and what results you’re getting.


Are You Ready to Go Keto?

The ketogenic diet is one of the more extreme diets out there, and it certainly isn’t for everyone.

That said, it’s not nearly as hard as it sounds, and once you learn to cook healthy, delicious keto recipes, you might not miss high-carb foods at all.

For many people, starting the ketogenic diet can turn out to be the most positive life-changing decision they ever made. You’d be hard-pressed to find a more effective diet for fat loss and productivity.

If you have any questions about the ketogenic diet or experiences you’d like to share, please share them in the comments. And for a deeper dive into the ketogenic diet– including how to build muscle on keto– read my interview with Luis Villaseñor of Ketogains.

Better Humans

Better Humans is a collection of the world's most trustworthy writing on human potential and self improvement by coaches, academics, and aggressive self-experimenters. Articles are based on deep personal experience, science, and research. No fluff, book reports, or listicles.

John Fawkes

Written by

Los Angeles-based personal trainer, online fitness & nutrition coach, and health & fitness writer. I also sing a pretty sick cover of The Poison Heart.

Better Humans

Better Humans is a collection of the world's most trustworthy writing on human potential and self improvement by coaches, academics, and aggressive self-experimenters. Articles are based on deep personal experience, science, and research. No fluff, book reports, or listicles.