What is the keto diet and how it helps your body burn fat through ketosis

Celebrities including Halle Berry and LeBron James have tried the ketogenic diet.

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Celebrities including Halle Berry and LeBron James have tried the ketogenic diet.
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photominer/Shutterstock

Compared to the low-fat craze in the ’90s, the ketogenic diet seems to go against all diet logic. Because instead of cutting out fat, you eat large amounts of it for every meal.

Research shows that this diet can be effective and help fight diseases related to obesity. That said, the keto diet is not for everyone. Here’s what you need to know.

The ketogenic diet has been around for almost 100 years

The ketogenic diet was first introduced in the 1920s as a way to treat epilepsy, a seizure disorder. Medical professionals used the diet for two decades until modern epilepsy drugs were developed and it fell out of favor by the 1950s.

That was it for the ketogenic diet for over half a century. Then, about 15 years ago, the diet reemerged. This time as a treatment for obesity and type 2 diabetes.

But even people who are not obese or have type 2 diabetes have adopted the ketogenic diet at some point, including celebrities like Halle Berry, Vaness Hudgens, and LeBron James.

How the keto diet works

The way it works is that you eat mostly fat and very few carbohydrates. A typical ketogenic diet consists of 75% fat, 20% protein, and 5% carbs. Compared to the average American diet which is 33% fat, 16% protein, and 51% carbs. On keto, common foods include:

  • Meat
  • Eggs
  • Full-fat dairy
  • Leafy greens and non-starchy vegetables
  • Nuts
  • Avocadoes
  • Olive Oil
  • Small amounts of berries

When you follow the ketogenic diet, your body stops relying on carbs as the main source of energy, which sends your body into ketosis. Ketosis is when your metabolism changes to burn fat for energy instead. This can lead to a loss of body fat, which can help prevent or improve medical conditions related to obesity like type 2 diabetes.

That’s because, on keto, your body may also become more sensitive to insulin, a hormone that helps balance your blood sugar. A 2017 review of nine studies found that people with type 2 diabetes on a low-carb diet generally could control their blood glucose levels better than diabetes patients on either a normal or high-carb diet.

The keto diet starts with weight loss, then evens out

When following the keto diet, weight loss can vary from person to person, says Jeff Volek, a registered dietitian and professor at Ohio State University. “When people with excess weight start a ketogenic diet, they typically lose about 6 to 8 pounds the first week, then about 1 to 2 pounds per week thereafter,” Volek says.

However, some people who go on keto reportedly suffer from some initial side effects including:

  • Bad breath
  • Constipation
  • Headaches
  • Nausea
  • Vomiting
  • Trouble sleeping

The initial weight loss is partly due to losing water weight because you tend to retain less water on a low-carb diet. And some studies suggest that you may not continue to lose weight on keto long-term. Some call this the “keto plateau” which is when you stop losing weight altogether.

Why the keto diet is hard to sustain

Volek says that the keto diet is safe for many people to try and that it may mimic the way early humans ate. However, Volek says that in some cases, you should proceed with caution. “If you have diabetes and are using diabetes medications to control blood sugar, you should work closely with your physician in order to adjust medications appropriately.”

The keto diet can be very restrictive and may be difficult for people to stick to, says Little. “The average ‘healthy’ person probably does not need to follow a keto diet but they could probably benefit from reducing their intake of refined/processed carbohydrates.”

Who shouldn’t try the keto diet

The ketogenic diet isn’t necessarily for everyone. Take kids, for example. Nutritionists recently told Insider that putting children or teens on the keto diet – or any restrictive diet – can lead to nutritional deficiencies and eating disorders.

Moreover, keto isn’t great long-term if you have, or are at risk of, heart rhythm problems. A large 2019 study, published by the American College of Cardiology, that involved medical records of nearly 14,000 people reported that people who don’t consume many grains, fruits, and starchy vegetables for years at a time, are at a higher risk of developing a heart condition called AFib.

Even if you’re otherwise healthy, long-term keto could lead to vitamin B and C deficiencies, since many foods rich in these vitamins – like beans, legumes, and fruit – are also high in carbs. And if you’re not getting the right nutrients, keto may actually lead you to gain weight, not lose it.

Bottom line: The keto diet is not for everyone and you should speak with a certified nutritionist before starting it, especially if you have a medical condition that the diet may affect.

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