What's the Deal With the Keto Diet?

Everything you need to know.

April 25, 2019

Peruse the aisles of Whole Foods, or the menu at your local smoothie shop, or the mosaics of health and wellness Instagram, and you’re likely to come across the word “keto”. Short for ketogenic diet, keto is a low-carb, high-fat diet in which up to 90% of your daily caloric intake comes from fat. It was first used in 1921 to treat epilepsy, but in recent years, it’s gone mainstream—so much so that 50% of all food-related Google search terms in 2018 had the word “keto” in them.

So how does it actually work? And is it safe? Let’s get into it.

How Does the Keto Diet Work?

In its natural state, our body relies on sugar, or glucose, for fuel. We typically get those sugars from carbohydrates like grains, fruits, vegetables, and legumes. On the keto diet, however, your body is deprived of those carbohydrates—and the glucose that’s made out of them—and turns to another type of fuel: ketone bodies, or ketones. Ketones are a type of fuel made in the liver, and they’re made out of stored fat.

But to get your body to produce ketones and burn fat for energy instead of carbohydrates—a state called ketosis—you have to limit your carbohydrate intake to fewer than 20 to 50 grams a day. (For context, a banana has around 27 grams of carbohydrates.) The low-carb, high-fat regimen in the keto diet is meant to get your body into ketosis—and keep it there.

Join The Conversation

Top Comment:
“Lost eighty pounds in eight months - and more importantly, I've stopped having gout flare ups (I used to get them every three months). Dirty Keto (relying on protein as well as fats, and just heavily limiting carbs) is a great fit for me - and is fairly sustainable!”
— Ipsum

Transitioning into ketosis, however, takes a bit of time—usually between two and seven days. During that time period, people have reported experiencing what is now known as the “keto flu”: nausea, digestive issues, low energy and mental function, headaches, and trouble sleeping. They also oftentimes develop what is called “keto breath,” in which your breath smells like nail-polish remover (turns out acetone is one of the ketones your body produces). Many of those side effects are caused by dehydration, which occurs as your body gets rid of the fluid that’s normally needed to process carbohydrates; staying hydrated with both water and electrolytes is therefore very important.

Once your body is in ketosis, large amounts of fatty acids are released from your body’s fat stores and transferred to the liver. The liver then oxidizes those acids and turns them into ketones, which are burned for fuel instead of sugar. As long as the body is deprived of carbohydrates, it will stay in ketosis.

In this metabolic state, blood sugar and insulin levels go down—making keto a diet that doctors sometimes recommend for those with type II diabetes. For some people, the process can also lead to rapid weight loss and a sped-up metabolism, which is why it’s also sometimes medically recommended to people with severe obesity.

What Do You Eat on the Keto Diet?

There’s a reason that the keto diet has become synonymous with butter-laden coffee and various other “fat bombs”: you’re eating a lot of fat on it. Keto-diet meals are typically made up of 70-80% fat, 20% protein, and 5% carbohydrates. (The normal American diet, for contrast, is around 55% carbohydrates.)

That fat can come from any number of sources: nuts, seeds, avocados, olive oil, butter, coconut oil, cocoa butter, lard, cheese, etc. Both lean and fatty proteins are fair game, too: think beef, bacon, other pork products, fatty fish, tofu, eggs, and poultry. Vegetables are limited to leafy greens, cauliflower, broccoli, brussels sprouts, asparagus, peppers, onion, garlic, mushrooms, cucumbers, celery, and summer squash.

And fruits are generally avoided, with the exception of small portions of berries. Other carbohydrates, like bread and grains, and foods high in sugar, like candy and pastries, are a no.

What Are the Risks of the Keto Diet?

Since the keto diet involves overhauling a major bodily process, there are some medical risks associated with it. First, it’s high in saturated fat, which is linked to heart disease; Kathryn McManus, the director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital, says that you should limit saturated fats to 7% of your daily calories while on the diet. It can also lead to liver problems—the liver can be overwhelmed by the amount of fat to metabolize—as well as digestive issues, due to the high levels of fat and comparatively low amount of fiber.

People on the keto diet also may experience dehydration and electrolyte disturbances, as ketosis can throw off the balance of your body’s minerals. Mood swings are also reportedly pretty common: “The brain needs sugar from healthy carbohydrates to function. Low-carb diets may cause confusion and irritability,” McManus says.

It’s also important to note that the long-term effects of the keto diet are unknown; there isn’t enough data to say what the effects are after two years. Medically, it’s generally recommended that keto-dieters stay on it for a minimum of two to three weeks and up to six to twelve months.

Who Is the Keto Diet For?

The keto diet is medically recommended for people with type II diabetes, people with a body-mass index over 40, and people who have treatment-resistant epilepsy. In any situation, though, the diet should be done under the guidance of a medical professional.

In Conclusion

Despite its ubiquity on Instagram and across health-and-wellness media, the keto diet is serious stuff. Some people will feel great on it; others will be miserable; still others will see a wide range of effects on their weight and health. If you do decide to try it, make sure to do so in consultation with a professional—and listen to your body! Only you can decide what works best for you.

Have you ever tried the keto diet? Are you contemplating it? We'd love to hear your thoughts in the comments!

See what other Food52 readers are saying.

  • Alina Mereuta
    Alina Mereuta
  • miriamnz
  • Chris Boore
    Chris Boore
  • Ipsum
  • Whiteantlers
Brette Warshaw

Written by: Brette Warshaw

I'm a reader, eater, culinary thrill-seeker, and food nerd.


Alina M. March 22, 2020
Keto diet is very good if you take care. Read more here: https://yve-style.com/ketogenic-diet/
miriamnz March 1, 2020
Can people link to their saved recipes on food52 that are keto? That would be really helpful.
Chris B. December 29, 2019
I started on ketogenics about 17 months ago after seeing the body changes in my son-in-law after he had been on it for about three months. My wife and I are both doing it and this is helpful because we support each other. I stayed pretty strict with it for the first year and lost 36 lbs. More importantly, I feel so much better. I never have energy peaks and valleys that used to plague me almost daily when I was on a more "normal" diet. I also got more dedicated to strength training, trying to get to the gym with a personal trainer twice a week. It is difficult sometimes because I travel for business weekly. I will be turning 69 in March and have gotten into great shape. I have allowed myself a few cheats in the last few months and, as a result, my weight loss has stalled. I am not gaining weight though...and still feel great. One year after starting keto I went for my annual physical and my blood work was perfect and my cholesterol was steady...basically the same levels sine I started monitoring it about 10 years ago. My wife has had a similar experience. I'd like to lose another 5-10 lbs, but I am excited about the results so far. I have never dieted before because I love to cook and all of the typical low-fat diets never made any sense to me. It is so boring and flavorless to exclude fat. It has stretch my cooking imagination too because have always been good at making sauces. So, I've had to learn new techniques for thickening sauces without using starches like flour, cornstarch, arrowroot, etc. I use cream cheese quite a bit. Sometimes I will simply reduce cream and stock into a flavorful, thick creamy sauce. If I don't want the sauce to be so creamy, I have learned to utilize xanthin gum. One other plus about keto is that there isn't a prohibition for alcohol...and I do enjoy a good cocktail. Again, this takes a bit of creativity.
Simple syrups and other sugary ingredients are virtually eliminated and substitute with stevia drops or another plant based sugar substitute. And, I am a bourbon & rye guy...and there are no restrictions there. Anyway, ketogenics has worked for me. I don't understand the controversy because from my own research, sugar is the real killer...not fat. High sugar intake from so-called low-fat, light, no-fat products that remove fat and replace it with sugar are the big health culprit and one of the causes for the high incidence of obesity and type-2 diabetes in the U.S.
Ipsum April 26, 2019
Lost eighty pounds in eight months - and more importantly, I've stopped having gout flare ups (I used to get them every three months). Dirty Keto (relying on protein as well as fats, and just heavily limiting carbs) is a great fit for me - and is fairly sustainable!
Whiteantlers April 25, 2019
I've lost nearly 100 pounds over 18 months following a ketogenic way of eating. I am allergic to the protein in eggs and casein and lactose in dairy products so I've had to do work arounds with those issues. I feel wonderful, I sleep well, I have tremendous amounts of energy and spend far less on groceries than when I was eating a standard American diet.

For me, an average day of eating would be several cups of hot tea for breakfast with a bit of unsweetened almond or macadamia milk, a protein (scallops, beef, chicken or fish), a cup or more of a non starchy vegetable dressed with non-dairy butter and a medium or large mixed green salad dressed with oil and vinegar or lemon juice.

I don't usually eat dinner because I am not hungry. If I do feel hungry, I weigh out a portion of nuts or have some dairy free yogurt. A few times a month, I will eat a piece of fruit or make a fruit smoothie if I am craving that.

I use MyFitnesspal to track my calories and macros. I do "cheat" a few times a month and eat and drink whatever I please but have found that foods that used to have a strong siren song don't really call out to me any more and more than 2 alcoholic drinks make me very sleepy. My challenge every day is eating enough rather than over eating because I have found that this way of eating does not leave me constantly hungry or unsatisfied.

Like anything else, this is not a fix all way of eating for everyone, but it sure as hell works for me.