In the world of nutrition, the ketogenic diet is enjoying its moment as diet du jour. Google trends show a sharp uptick in searches for the ketogenic diet since 2016. Almost 550,000 people subscribe to the r/keto subreddit. And when I searched #keto on Twitter, I found an endless stream of modified keto recipes and stories claiming successful weight loss.
Alicia Vikander, the new Lara Croft in Tomb Raider, and Silicon Valley bros have reportedly used the diet to change their bodies. You can even buy keto dog food. According to some advocates, keto diets are a one-size-fits-all solution for obesity and the hunger that comes from traditional weight loss diets. On the other hand, a panel of nutrition experts ranked the ketogenic last (along with the Dukan Diet) among 38 other diets in US News and World Report’s annual diet rankings.
How did this diet, which was first developed in the 1920s as a treatment for children with epilepsy (and has been shown to reduce seizures in patients whose epilepsy symptoms aren’t responding to other medications), become the diet du jour, and why such a discrepancy between its fandom and expert opinion? Let’s take a closer look at what “going keto” entails.
First things first: To understand keto, you have to know a bit about how the body burns energy.
The main objective of the ketogenic diet is to get the body to start relying primarily on fat for energy. In general, our bodies are predominantly fueled by glucose (also known as blood sugar), which we get from carb-rich foods (bread, cereal, pasta, rice, etc.). The digestive tract breaks these foods down into glucose so it can be converted into adenosine triphosphate (ATP), which is the chemical our bodies can use for energy. But when the body is deprived of carby delights, it finds other ways to make energy, and one way is a process called ketogenesis. During ketogenesis, the body turns to fat for energy; the liver breaks it down into ketones, making it a usable energy source, Amy M. Goss, Ph.D., assistant professor at the University of Alabama at Birmingham’s Nutrition Obesity Research Center.
When you deprive your body of glucose, either by fasting or by following a very low carb diet (VLCD) like the ketogenic diet, your body enters the metabolic state called ketosis—it’s primarily getting fuel by burning stored fat.
This means that to achieve ketosis, you have to limit your carb intake to less than 50 grams per day (most people should reach ketosis within a week of following the diet). To put this in perspective, the low-carb diet you’re most familiar with—the Atkins Diet—recommends about 130 grams of carbs per day. Also for reference, one bagel has about 55 grams of carbs.
Following a ketogenic diet, your food intake would be roughly 5 to 10 percent carbohydrates, 15 percent protein, and 75 to 80 percent fat. This would be a pretty seismic shift for most people who follow a standard American diet; according to a 2016 report by the CDC, the average American adult’s diet is 50 percent carbohydrates, 16 percent protein, and 34 percent fat. Your average day on a ketogenic diet might include eggs, cheese, assorted meats and small amounts of nuts and avocados, and modest amounts of vegetables that are low in carbs, like spinach and lettuce.
While following keto, you’re encouraged to eat as much fat as you want, no matter the source (e.g., butter, olive oil, meats, cheeses), until you feel full. Fat can have a strong satiety effect, but following this recommendation may not be comfortable for everyone. According to recent research, fatty foods may increase feelings of nausea and bloating for some people. Beyond potential physical discomfort, it also might not be emotionally comfortable for everyone—after all, keto is still a restrictive diet, which typically is not a good choice for anyone with a disordered relationship to food and eating. And as with any restrictive dietary plan, following a ketogenic diet can present challenges when it comes to social occasions, celebrations, office parties, meals out, etc. It also might be necessary to limit or avoid culturally relevant foods on the diet in order to stay in ketosis. For still other people it will be tough to sustain because carbs aren’t only delicious, they’re omnipresent. Avoiding them day to day means fastidious meal prep and planning, and planning for social events that include food or eating.
Many people believe the ketogenic diet is great for weight loss. But it’s actually a bit more complicated than that.
Before we dive further into weight loss, a note: Weight loss isn’t for everybody, and neither is following a specific, restrictive eating plan. If your goal is to lose weight, that’s fine, but your health matters more than a number on a scale (and if you have a history of disordered eating, you should discuss any plans to change your diet with a doctor first). In addition, successful long-term weight loss is the product of many factors: Your physical activity, how much sleep you get, stress management, and other factors like medical issues and hormones all play an important role. What you eat is just one part of the weight loss puzzle.
If you have been looking for a weight loss plan, however, you’ve probably heard of one of the ketogenic diet’s biggest claims to fame: the quick results it supposedly produces. Some people report losing as much as 10 pounds in the first two weeks. But this weight loss is likely to be mostly water weight, not fat melting away, meaning you stand to gain it back once you replenish fluids. The ketogenic diet can act as a diuretic, causing water loss from glycogen storage in the liver, muscles, and fat cells. Keep in mind that for most people, about ½ pound to 2 pounds per week is considered safe.
As far as keto’s track record with longer term weight loss, a systematic review and meta-analysis that looked at 13 randomized trials that lasted at least a year showed that people who followed the ketogenic diet recommendations lost, on average, 2 more pounds compared to those who followed lowfat ones. But some experts say that weight loss from a keto diet probably isn’t from any specifics about the diet itself. If the ketogenic diet aids weight loss, says Brian St. Pierre, R.D., director of performance nutrition at Precision Nutrition, it’s because it might enable some people to maintain a caloric deficit.
“I let folks know that the ketogenic diet approach can absolutely work, though it’s not through some magic of carb restriction. Keto works for some folks because they enjoy fat-rich foods, find them satisfying, and feel their best eating this way. This allows them to control their overall intake and fuel their activity,” says St. Pierre.
And of course there are other health considerations to keep in mind beyond weight loss.
Remember: Just because something fits your macros doesn’t mean it’s super healthful and providing a balance of nutrients. High consumption of certain foods (like hot dogs, bacon, and other processed meats) and under consumption of healthier foods (nuts, seeds, vegetables, fruit, whole grains) are linked with certain health conditions and death from heart disease, stroke, and type 2 diabetes, and that’s important to keep in mind even if we don’t necessarily have a causal link or recommended limit.
The American Heart Association’s recommendations for controlling cholesterol include getting more fiber and limiting your intake of saturated fat, both of which would be extremely difficult on a ketogenic diet. While it’s true that research around saturated fat is still evolving, making room for good sources of fiber and unsaturated fats, which reduce the risk of cardiovascular disease, and allowing for a more balanced intake of nutrients, is ideal. In any case, you should check with your doctor before you start a ketogenic (or any new) diet, especially if you have any health conditions like high blood pressure or high cholesterol.
And although in the short term, ketogenic diets seem safe for healthy people, we also lack long-term data on the diet, so it’s hard to confirm long-term safety with certainty. Complications seen with kids maintaining a ketogenic diet for epilepsy, for example, included kidney stones, constipation, gastrointestinal issues, pancreatitis, and vitamin D and calcium deficiencies.
As with any eating plan, keto comes with its own unique lifestyle requirements.
If carbohydrates—either processed packaged sweets or nutritious whole foods—are your jam, the ketogenic diet will, at best, take some getting used to. And at worst, it could be a total nonstarter. The diet will necessarily steer you away from foods that have added sugar, are calorically dense, and don’t offer much in the way of nutrition, like cookies, cakes, white bread, sugary cereals, fries, chips, crackers, and sugary drinks, which are all high in carbohydrates. (It’s important to keep in mind that it’s not necessary to totally avoid all processed carbs; healthy, balanced diets can in fact include processed foods and sweets). On the other hand, the diet also creates an unneeded aversion to nutritious foods that are also high in carbohydrates, like fruit, sweet potatoes, butternut squash, beans, lentils, and whole grains.
When some people attempt a ketogenic diet, they experience the “keto flu” during the period of time their bodies are adapting to the diet. This is a period of feeling lightheaded, lethargic, irritable, and unmotivated. “It typically lasts one to three days, and may very well be just the result of dehydration. A drop in insulin can impact renal sodium retention such that sodium and fluids are excreted more readily. This also acts to lower blood pressure,” Goss says.
As for how it feels to follow the diet, St. Pierre says it will vary from person to person; as with most diet-related things, whether or not a way of eating works is in the eye of the beholder. He’s seen some people feel fine, but that “some clients have found it causes brain fog and lethargy, decreases their performance, disrupts their regular bowel movements, and makes them feel generally crappy,” he says. Some keto adherents also report having pretty atrocious breath, which might be caused by the presence of acetone, a ketone and byproduct of fat metabolism, in exhaled breath.
The TL;DR is pretty much the same as it is with any other eating plan or diet: It might be useful and effective for some people, but it’s certainly not a guaranteed weight loss panacea.
Like most diets, the ketogenic diet is not a one-size-fits-all answer to all of our health and weight hopes and dreams. It might be enjoyable for some people, especially in the short term, but that doesn’t mean it will be a fit for everyone. The experts we talked to for this post agreed that although it may lead to short term (water) weight loss, it might not be optimal as a sustainable weight loss solution. St. Pierre explains the way he sums it up for his clients: “I let them know that there isn’t a universal approach that works for everyone, and that restrictive diets like keto can be hard for folks to stick to long-term.”
At the end of the day, adherence and enjoyment are the two-key lifestyle change techniques that will produce the best outcomes for any eating plan. Find an approach that’s enjoyable, healthy, and that you can maintain. If a ketogenic diet is that for you, and you’ve figured out a healthy keto plan that works for you, bravo.