There are several predictors of how fast or slow a person’s metabolic rate will be. These include the amount of lean muscle and fat tissue in the body, age, and genetics. Women tend to burn fewer calories than men. Having a higher metabolic rate means your body uses food for fuel (instead of storing it as fat) more quickly. But you can still gain weight if you consume more calories than your body needs. Counterintuitively, heavier people generally have higher metabolic rates than skinny folks to meet the fuel demands of their larger bodies. Meticore.