You must have noticed that some of your friends eat a lot of sugar-based foods, fried foods, or cold drinks. Yet, they manage to have a flat stomach, the reason being they have a very high metabolic rate. If your metabolism is not good, you may have a bloated stomach. Thyroid conditions, diabetes, and other medical conditions can be the reasons for slow metabolism.
In a way, moderate-intensity physical activity is that "magic pill" a lot of people are looking for, because the health benefits go beyond keeping your waistline trim: Not only can it reduce your risk of cancer, stroke, diabetes and heart attacks, but studies have shown that physical activity can significantly improve the moods of patients with major depressive disorders.