If you keep up with health trends or are trying to lose weight, you’ve probably heard of the ketogenic diet — a regimen that involves cutting most carbohydrates from your diet to induce ketosis and turn your body into a “fat burning machine.” In this metabolic state, deprived of the carbohydrates that typically power its processes, the body starts burning fat for fuel.
What Can You Eat on the Keto Diet?
To achieve this state, the ketogenic, or “keto” diet, limits carbohydrate intake to just 5 percent of overall caloric intake. On the diet, a person consumes a moderate amount of protein (about 10 to 20 percent of calories) and a lot of fat (70 to 80 percent of calories) — meaning in theory, you can eat all the butter, oil, and meat you want. Limiting carbs is the key to potentially achieving the desired metabolic state of ketosis.
“The main macronutrient is fat,” says registered dietitian Haley Hughes MS, RD, CDE. In order to consume most of your calories from fat, you must maintain a strict diet of little to no carbohydrates at all and “include plenty of nuts, nut butters, coconut, non-starchy vegetables, avocado, cheese, oils, and some protein sources,” Hughes says.
Proteins such as lentils, beans, and peas are typically banned on the keto diet, since these foods contain carbohydrates.
Keto dieters should keep in mind that vegetables such as squash, potatoes, and carrots contain carbohydrates and should either be extremely limited or avoided entirely.
How Does It Work?
“Tissues in the body utilize either carbohydrates, fat, or glucose,” explained Amy S. Margulies, RD, CDE, LDN. “When dietary sources and stored glucose becomes low, the body finds ways to fuel the body’s tissues (i.e. brain, muscles, organs, etc.). Ketosis is a metabolic state that occurs when dietary carbohydrates are low enough that the body relies solely on fatty acid oxidation and ketone metabolism to produce energy.”
When the body is flushed with ketones, this indicates that the body is resorting to burning fats for fuel.
Where Did It Come From?
Despite how it’s most commonly used today, the keto diet did not originate from the intention to burn body fat. Instead, the diet was used to treat disease in patients with chronic illness.
“The ketogenic diet was introduced in the 1920s to mimic fasting regimens used to treat epilepsy,” recalled Margulies. “More research really expanded on the ketogenic diet starting in the late 1990s to determine if it would be beneficial in treating any other conditions, including cancer, Alzheimer’s, depression, polycystic ovarian syndrome (PCOS), and metabolic syndrome.”
Are There Any Benefits?
For people who are not experiencing a chronic illness, whether or not the diet is beneficial is unclear.
“Due to the types of foods consumed, blood sugar levels are lowered and some professionals recommend it as a more effective way to manage and prevent diabetes,” Margulies says. “Additionally, the brain can function well on ketones; therefore, some people follow a ketogenic diet simply for mental focus and clarity.”
Margulies also pointed out that some who attempt the diet report increased energy levels and decreased hunger in the short term.
However, some dietitians are skeptical that it maintains any long-term benefit. “It may have short-term rewards in weight loss,” conceded registered dietitian Jackie Arnett Elnahar, “but it is without long-term sustainability or benefit to overall health.”
There is not sufficient research to confirm whether the diet has a long-term impact on body weight, cholesterol, blood pressure, or risk of disease.
Are There Any Complications?
In a word, yes. Carbohydrates are the body’s most easily accessed source of fuel. So when you eliminate these foods, your body will experience some side effects.
“Many people experience some changes in the way they feel, especially in the first days or even weeks of doing a ketogenic diet,” explained Ginger Hultin, MS, RDN, CSO and Arivale coach. “Symptoms range from lightheadedness, fatigue, and headaches to GI troubles like diarrhea or cramping.”
Hultin noted that some people experience their exercise routines that used to feel doable begin to feel more taxing and exhausting.
“There is a possibility of kidney damage, nutritional deficiencies, and side effects including constipation, dehydration, fatigue, and nausea with this diet,” Hultin concluded. “Shifting to keto on certain medications or with conditions like diabetes or high blood pressure can be dangerous.”
The ketogenic diet certainly is not for everyone — to learn more about why the keto diet may or may not be right for you, read our guide here.