When you eat more calories than you burn, you create a calorie surplus and your body is forced to store that extra energy as body fat (or build muscle if you’re involved in a strength training routine). Where your body stores extra body fat is determined by genetics and out of your control. When you burn body fat for energy, you don’t get to decide where that fat comes from (spot reducing). All you can do is combine a calorie restricted diet with exercise to force your body to burn fat from all over and everything, including your gut, will become toned.