But by influencing amount of body fat and fat distribution, genes can make you more susceptible to gaining weight. Your body shape, for example, generally falls into one of three categories ectomorph, endomorph or mesomorph. The slight frames of ectomorphs reflect a low capacity for fat storage. Endomorphs have the most fat-storage capacity. And mesomorphs have an ability to store fat that falls somewhere in between.
Fat storage is also more evenly distributed.
You may never have the lean body of an ectomorph or the muscular build of mesomorph regardless of your weight. Most people, however, are a combination of all three, with a tendency to be more like one or two of them. Some people have a naturally high metabolic thermostat they tend to burn more calories than average even when they're asleep. Other individuals need fewer calories for the same physical activity. These metabolic differences alone, however, aren't great enough to account for weights that exceed the healthy ranges in weight tables.