The keto diet emphasizes weight loss through fat-burning. The goal is to quickly lose weight and ultimately feel fuller with fewer cravings, while boosting your mood, mental focus and energy. According to keto proponents, by slashing the carbs you consume and instead filling up on fats, you safely enter a state of ketosis. That’s when the body breaks down both dietary and stored body fat into substances called ketones. Your fat-burning system now relies mainly on fat – instead of sugar – for energy. While similar in some ways to familiar low-carb diets, the keto diet’s extreme carb restrictions – about 20 net carbs a day or less, depending on the version – and the deliberate shift into ketosis are what set this increasingly popular diet apart. In fact, other eating plans are pulling in keto elements, so you can find versions like eco-keto and at least one commercial diet that incorporates keto-friendly products.

The keto diet has its roots in the decades-old therapeutic ketogenic diet. Clinically, the ketogenic diet is used in neurologic medicine, most notably to reduce hard-to-control seizures in children. Studies also suggest possible benefits in other brain conditions such as Parkinson’s and Alzheimer’s diseases.

Fairly recently, the diet was introduced as a weight-loss diet by an Italian professor of surgery, Dr. Gianfranco Cappello of Sapienza University in Rome. In his 2012 study, about 19,000 dieters received a high-fat liquid diet via a feeding tube inserted down the nose. The study showed an average weight loss of more than 20 pounds in participants, most of whom kept it off for at least a year. The researchers reported a few minor side effects, like fatigue.

The medical community is taking note of the high public interest in keto. An article in the Jan. 16, 2018, Journal of the American Medical Association summarized several areas of promise: Many people feel less hungry on the high-fat keto diet and so may naturally reduce their overall calorie intake. Beyond weight loss, there was good news for diabetes management, with improved insulin sensitivity and blood-sugar control for people following a ketogenic diet in an early, still-ongoing study. However, an editorial appearing online July 15, 2019, in JAMA Internal Medicine concluded that “enthusiasm outpaces evidence” when it comes to a keto diet for obesity and diabetes.

Today, several versions of the keto diet (using real food) are detailed in books, blogs and Facebook posts. The common thread is choosing high-fat foods coupled with very low daily carbs. Guidebooks include “The Complete Ketogenic Diet for Beginners” by Amy Ramos and “The Keto Diet: The Complete Guide to a High-Fat Diet” by Leanne Vogel.