The ketogenic diet is a high-fat, very-low-carbohydrate eating plan that aims to bring about weight loss by causing your body to enter a state of fat-burning ketosis. Although it’s become popular during the past decade or so as a weight loss strategy, it was originally designed 100 years ago as a way to reduce seizures in people with epilepsy.
The keto diet not only promises weight loss, but also claims to reduce hunger and help balance blood sugar. However, it can be a difficult protocol to follow. “One of the cons of the keto diet is that it has very strict rules,” says Melissa Majumdar, a certified specialist in obesity and weight management and a bariatric coordinator at Emory University Hospital Midtown in Atlanta. “I don’t know anybody who would be able to follow this diet for a long period of time.” It’s also risky for people with certain health conditions.
A keto diet is low enough in carbs and protein and high enough in fat to force the body to burn stored fat instead of consumed carbohydrates for energy. To trigger ketosis, a diet typically must contain a maximum of only 50 grams of carbohydrates per day. (A slice of whole-wheat bread, for example, contains about 15 grams of carbohydrates, and a medium banana contains about 29 grams of carbohydrates.) Overall, carbohydrates contribute fewer than 10% of calories in a keto diet. The remainder comes from fat (70% to 80% of daily calories) and protein (about 10% of daily calories or about gram per pound of body weight).
What Is Ketosis?
Your body prefers to burn glucose-containing carbs for energy. When carbohydrate-sourced glucose is not available, your body burns fat instead. To use fat for energy, your liver converts fat to substances known as ketones and burns those instead of glucose. When this process occurs, your body is in a state of ketosis.
Because your body prefers to burn glucose rather than fat, it may resist shifting into ketosis and will not do so unless you adhere strictly to carbohydrate and protein limits. It can take a few days, sometimes longer, to achieve a state of ketosis, and you must continue to limit carbohydrates and protein strictly in order to stay in ketosis. “If you don’t follow the rules, you go out of ketosis,” says Majumdar, who is also a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.
Types of Keto Diets
Various types of diets call themselves keto diets. However, some would be more accurately described as “keto-ish” or low-carb diets because they’re too high in carbohydrates to induce ketosis regularly. True keto diets are very low in carbohydrates, high in fat and moderate in protein.
Well-known keto-style diets include the Atkins and South Beach diet. Other low-carb diets may claim to be keto diets, but unless they include fewer than 50 grams of carbohydrates daily and only a moderate amount of protein, they may not induce ketosis reliably. In addition to limiting carbohydrates, you have to make sure you avoid eating too much protein as well, because protein can interfere with ketosis.