A ketogenic diet can be an effective style of eating to help manage specific medical conditions (such as autoimmune disorders), but the diet doesn't burn more fat. When you are in ketosis (eating, generally, less than 30 grams of carbs per day), your body will burn the fat you eat as fuel. But, just because you burn more fat you eat does not mean you burn more fat on your body.
Disclaimer: If there’s one thing we know with certainty about diets it’s this – there is no such thing as a perfect diet. Most diets work if you stick to them, so you can rest assured that you need to spend less time finding the “best” diet and more time reviewing what a diet requires you to do and if you think you can stick to it for an extended period.
Diet success is dependent on your adherence, which is determined by a variety of factors, including your lifestyle, daily schedule, food preferences, environment, stress, sleep, genetics, and several other factors.
The ketogenic diet was designed to help treat epileptic seizures in children. Its mechanism is known as ketosis — the process by which your body runs on fat because you don’t have enough carbs or glucose.
On paper, it almost seems too simple. Eat more fat (and fewer carbs and protein), and your body will burn the fat (instead of storing it) because you need to use the fat as fuel.
But fat loss doesn’t happen on paper. The claims about keto superiority for fat loss and muscle gain exaggerated. But, that doesn’t mean the diet is without value.
Instead of trying to figure out if the ketogenic diet is better than other diets (it’s not), you should make sure you understand exactly how it works (low carb is not necessarily ketogenic) and if it’s a good fit for your lifestyle and goals.
How The Ketogenic Diet (Really) Works
The ketogenic diet is a type of low-carb diet. But not all low-carb diets will put you into ketosis. Understanding this concept is a critical distinction because thinking you’re in ketosis (when you’re not) can lead to a lot of unnecessary diet frustrations (and potentially weight gain).
In a traditional ketogenic diet, you eat 80 percent of your daily calories from fat. The remaining 20 percent consists of protein and carbohydrates—but most of it protein. When you’re in ketosis, you’ll typically eat a maximum of 20 grams per day (that’s less than what you’ll find in an apple or banana), according to Andy Galpin, Ph.D., C.S.C.S., C.P.T., associate professor of kinesiology and director of the Biochemistry & Molecular Exercise Physiology Lab at California State University, Fullerton.
So if you’re following a low-carb diet where you eat 50-100 grams of carbohydrates (still very low according to a review from Tulane University, which suggests that eating 225 grams of carbs on a 2,000-calorie diet would be considered “low carb”), then you’re still not in ketosis. And if you genuinely want to see the benefits of the ketogenic diet, you need to be in ketosis for your body to burn fat as fuel.
When you only have 20 percent of calories for non-fatty foods, you quickly discover how limited you are with food options. Most people think you can eat seemingly unlimited amounts of bacon and steak. But those foods are filled with protein. And – as you’ll learn – having too much protein can take your body out of ketosis.
Carbs and glycogen (or carbs stored in your liver and muscles) are your body’s preferred and most efficient energy source. Once depleted, your body must find other energy sources.
When you cut carbs drastically -- as one does on a keto diet -- you can put the body in a state of ketosis. In this state, your liver is forced to convert fat into fatty acids and ketones — compounds the body can use to produce your body’s preferred source of energy, which is called ATP, Galpin explains.
And that's the primary difference between the ketogenic diet from other low-carb approaches such as Atkins, and why the diet revolves around such a high intake of dietary fat: without it, your body cannot produce the ketones needed to keep you functioning.
If your body is not in a state of ketosis, you’re technically just following another low-carb diet, meaning your body is not running on ketones. And all that carb-depletion isn’t going to work the way you intended.
Through ketosis, your body becomes what many refer to as “fat adapted,” meaning your body adjusts to what you’re giving it and uses fat for energy.
In a world of quick fixes and promises, this usually is not a quick process. Research suggests that it usually takes several weeks to occur, according to ketogenic diet researcher, Antonio Paoli, M.D., director of the Nutrition & Exercise Physiology Lab at the University of Padova in Italy.
What happens in the process of becoming fat adapted? Expect extreme fatigue, brain fog, and sluggish exercise performances. After all, your brain is the primary user of your body’s carbs and glycogen. Without that fuel, your entire central nervous system feels the effects.
It’s those effects on the neurological system that first popularized the keto diet. According to a 2014 review published in the Journal of Lipid Research, ketosis alters the activity of mitochondria in the brain of those with neurodegenerative conditions, which helps cut down on the frequency and severity of seizures.
Does Keto Burn More Fat?
When you’re on the ketogenic diet, you’re not burning more body fat.
You see, when you eat more fat, your body is going to burn more fat. The increase of fat in your body causes an increase of “fat oxidation” or the amount of fat you burn. Some people interpret this as an increase in fat loss. That's not accurate.
When protein and calories are balanced (as in, you’re comparing diets where total calories and protein are the same -- but fat or carb intake is different), there is no difference in fat loss between a keto diet and a non-keto/higher carb diet.
“To lose weight on the diet, you still have to consume fewer calories,” Galpin says. “There are no physiological shortcuts. Calories still matter, and while they aren't the only thing that matter for fat loss, you still have to maintain a caloric deficit to lose fat.”
So why do some people swear by “keto magic?” For starters, when you cut carbs, you are likely to see some immediate changes to your weight. A lot of this is due to a shift in water weight.
More importantly, Paoli notes that a ketogenic may aid in cutting calories by increasing feelings of fullness, but that potential benefit is not yet definitive.
But if you want to lose fat and hold onto your muscle, research suggests that the ketogenic diet might not be ideal (it can work, but it might be more difficult). That’s because you likely need more calories coming from protein than the diet allows.
A 2015 review published in Applied Physiology, Nutrition, and Metabolism showed that to retain muscle mass while cutting calories, protein intake should be about 25 percent of total daily calories, or about 5 percent more than all of the non-fat calories allowed to stay in ketosis.
The Ketogenic Diet and Performance
If you’re looking to improve your exercise performance, the ketogenic diet comes with mixed results.
In one Nutrients study, male cyclists who followed a keto diet for four weeks decreased their body fat percentages and improved their VO2max levels (the amount of oxygen they could take in and use in a minute), but their max power decreased.
But, most research seems to indicate no performance benefit if you’re performing high-intensity activities such as sprinting and weightlifting. It’s worth noting, however, that a lot of the studies on keto done to date have suffered from at least one big design flaw.
“A major problem with the research on the ketogenic diet is that a huge chunk of them don't establish whether study participants are actually in ketosis,” Galpin says. “Researchers often don’t draw blood to determine a state of ketosis and instead assume that participants were eating few enough carbs and enough fat that they were.”
Is It Safe For You?
For the most part, the ketogenic diet is safe for you to try. And if you struggle with a variety of health issues, it could have surprise benefits. The ketogenic diet has a lot of fascinating research on brain health and fighting autoimmune diseases. If you struggle with a variety of diagnosed health problems, the nature of the diet is promising. And if you don’t mind the rigorous rules, it can be an effective fat loss approach – just like several other diet methods.
The catch: the ketogenic diet can be incredibly strict to follow. Researchers have found that to be true even when adults attempt the diet to control their epilepsy. You might want to consider the difficulty of the diet before beginning. If people who have the highest degree of motivation to use the diet (those with epilepsy) find it hard to maintain, then there’s a high likelihood that it could be difficult for you too.
In no way is that meant to dissuade you from trying the diet. If high fat and super low carb sound easy or enjoyable, then it might be worth your time. After all, that’s the real diet secret. Research has shown over and over again that diet success depends entirely on your consistency.
Your biggest concern when considering the ketogenic diet might be protein. As we mentioned prior, low protein can make it hard to hold on to your lean muscle. But, if you overeat protein, then you can bump your body out of ketosis.
If you overeat protein during a ketogenic diet, your body could go into a state of ketoacidosis, in which keto acids (ketone-containing acids) accumulate and decrease blood pH, Galpin says.
When this occurs, symptoms include nausea, vomiting, excessive thirst, and confusion. In very rare cases, “extreme ketoacidosis” can be fatal.
While some may think a keto diet gives them license to go crazy on greasy, processed foods and still lose weight, it’s important to focus on getting dietary fats from whole, natural sources including red meat, eggs, avocado, nuts, olive oil, and dairy (although many forms of dairy have sufficient carbs to kick you out of ketosis, FYI).
It’s worth noting that, since these high-fat foods tend to be low in fiber, make sure you eat enough to prevent constipation and GI issues such as diverticulitis, Galpin says. He adds that most keto dieters require a fiber supplement to get enough fiber without going overboard on carbs.
Lastly, high protein intake can also increase keto dieters’ already-elevated risk of developing kidney stones. Despite many persistent myths, a high protein diet does not cause kidney problems. But, adding lots of protein to a ketogenic diet can potentially lead to kidney stones.
If you’re going to see success with the ketogenic diet, do your best to follow the rules as closely as possible, ideally under the supervision of a physician or registered dietitian, according to Paoli. While it might not be a superior diet, it can still be beneficial and safe for many goals and lifestyles.