David Sacks
Weight loss

Losing weight is difficult. Here's why keeping it off is even tougher.

Even after you lose weight, your body's level of the "hunger hormone" ghrelin stays high—and that translates to being hungry all the time.

Losing weight is hard enough when you're already overweight or obese. But once you finally arrive at your goal weight, keeping that weight off can be even more difficult: Only about 20% of people who lose weight end up maintaining that new, lower weight, research shows.

There are several reasons keeping weight off is difficult. Two significant causes: Your body's hormones like to keep you heavy, and your body typically defaults to conserving energy, according to recent research published in the American Journal of Physiology, Endocrinology, and Metabolism.

For the study, scientists put 34 patients who were morbidly obese on a two-year weight-loss program. At the end of the study period, all participants had lost weight (an average of 24lbs), but they were all also much hungrier on average than at the beginning. Researchers attributed the increased appetite to higher levels of the hunger hormone ghrelin. As people lose weight, the body produces more ghrelin; even when you "arrive" at a goal weight and maintain it, the body keeps ghrelin levels high. Furthermore, the researchers noted, a newly leaner body adjusts into an energy-saving mode because it needs less energy for basic functions.

"Someone who has weighed 80kg their whole life can eat more than a person who is 80kg after losing weight,” said Catia Martins, Ph.D., an associate professor in the Norwegian University of Science and Technology's department of clinical and molecular medicine. “The difference in the amount of food is about 400 calories—the amount of a good breakfast or four bananas.” She also notes because of our bodies’ attempt to get that weight back through increasing hunger and saving energy, that: "Obesity is a daily struggle for the rest of one's life. We have to stop treating it as a short-term illness by giving patients some support and help, and then just letting them fend for themselves."