Before There Was Keto, The Leptin Diet Was Huge

In the early 2000s, a trendy diet came on the scene that promised to help people "get more energy from less food." It was called "the leptin diet," and there was a rule book and list of suggested supplements to use along with the program.

The basis of the diet is pretty simple — all you have to do is follow five rules. They are: never eat after dinner; eat three meals a day without snacking; don't eat large meals; eat a high-protein breakfast; and limit carbs. If you've ever tried any kind of diet before, these guidelines might not seem that groundbreaking. But, unlike diets that focus on things like calories and ketosis, this diet allegedly targets leptin.

Leptin is a hormone that is made by fat tissue, and is involved in bodyweight regulation, explains Martin Myers, MD, PhD, professor of internal medicine at the University of Michigan, whose lab focuses on the biology of leptin. The more fat tissue a person has, the more leptin they make. Research has shown that leptin is involved in your feelings of hunger and satiety. "Leptin is effectively the fat cell’s signal to the brain that indicates the repletion of body fat stores," he says.

According to the leptin diet philosophy, you can "master" the hormone, and "break free from food obsession" by following the rules. Unlike the ketogenic diet, which has a list of foods that are considered okay and off-limits, the leptin diet simply encourages eating fresh, whole foods. But, for as much as we know about leptin, "it isn’t clear what the leptin diet has to do with leptin," or how these rules line up with the biology of leptin, Dr. Myers says.

What we do know is how dieting and calorie restriction impacts leptin levels in general. "Successful" dieting, in this case meaning dieting that results in weight loss, typically decreases leptin levels, Dr. Myers says. "When leptin falls — as in dieting or other forms of caloric restriction — the brain perceives a caloric need, and increases the drive to feed, as well as changing metabolism to burn fewer calories," he says.

In other words, the brain tries to compensate for the weight loss, to rebound to the weight before beginning a diet. This is one of the reasons why weight cycling is common in dieters. "The body doesn't recognize that excess that's not needed, so it'll do whatever it can do to defend that," Fatima Cody Stanford, MD, MPH, an obesity medicine physician at Massachusetts General Hospital, tells Refinery29. Contrary to popular belief, this is physiological, not related to willpower.

If you are at all concerned about the amount of leptin in your body, then your best bet would be to ask an endocrinologist or healthcare provider to measure your leptin levels and see how they stack up. People who are classified as obese, for example, are susceptible to a disorder called "leptin resistance," which is a lack of sensitivity to the hormone. The bottom line to keep in mind is that it's helpful to understand what leptin is, but it's certainly not a magical metric that will solve all of your problems.

What's interesting about the so-called "leptin diet" is that there's an emphasis on restriction, and you're discouraged to snack or eat outside of your set three meals. But these rules don't really take into consideration the other factors that influence our food choices, such as cravings or activity levels. Ironically, we know that restriction that typically precedes binge eating. So, this idea that you have to eat less in order to cure your "food obsession" is pretty outdated, not to mention harmful to your health and relationship to food.

In a world oversaturated by diets and health fads, it can be hard to figure out what's worth your time. But considering how our understanding of nutrition has evolved, the leptin diet might be better off left in the aughts.