Body fat builds up when your body takes in more calories than it uses. In simple terms, if you eat more food (energy) than your body burns, the extra gets stored as fat. The most common reasons for fat gain include an unhealthy diet full of junk food, sugary drinks, and fried items that add unnecessary calories. A lack of exercise also plays a big role — when you don’t move enough, your body stores unused energy as fat. Poor sleep can increase hunger hormones, leading to overeating, while stress triggers the release of cortisol, a hormone that promotes belly fat. Irregular eating habits, such as skipping meals or eating late at night, can slow down your metabolism. Additionally, hormonal imbalances, such as thyroid or insulin issues, can make it more difficult to burn fat effectively.