It seems to make sense that if you eat less food, you’ll lose weight. But that’s not necessarily the case, according to Dr. John B. Cleek, an internal medicine specialist with Roper St. Francis Physician Partners. Dr. Cleek points out that genetics are responsible for 50 to 70 percent of a person’s weight, but other factors contribute to what your bathroom scale tells you each morning. For example, if you don’t get enough sleep, your metabolism decreases and your appetite increases.