When you lose weight, you experience all sorts of changes in your body such as differences in your metabolism and hormone function. Scientists are still teasing apart the effects of all of these changes, but they do know that the majority of people who lose weight eventually put most of it back on. One study found that adults who had previously had obesity or were overweight but lost weight were more likely to keep that weight off after a year if they adhered to a Mediterranean Diet, rather than other types of diets. While what you eat seems to have a bigger impact on weight loss than exercise does, a consistently greater amount of exercise is likely to help you keep it off, according to a study of people who lost weight and kept it off for nine years. One way it may help is by increasing your sensitivity to leptin, the hormone that signals fullness, and reducing inflammation in your body.