Having a big stomach, even if you're otherwise skinny, can be due to several factors. Genetics, age, and lifestyle choices all play a role in the distribution of body fat. Some individuals may be predisposed to store more fat around their midsection due to their genetic makeup. Additionally, age-related changes in metabolism and hormonal fluctuations can contribute to increased belly fat. Lifestyle factors like a poor diet, lack of exercise, stress, and inadequate sleep can also lead to increased belly fat, even in individuals who are otherwise skinny.