Aging does play a role too. As you age, you lose muscle — especially if you're not physically active. Loss of muscle mass decreases the rate at which your body uses calories, which can make it more challenging to maintain a healthy weight. According to the 2015-2020 Dietary Guidelines for Americans, men in their 50s need about 200 fewer calories daily than they do in their 30s due to this muscle loss.
The stress hormone cortisol can really screw with your belly. The problem with cortisol is two-fold: First, the chemical makeup of cortisol causes the body to store visceral fat. Visceral fat is stored between your main organs and in the midsection and is the most dangerous type of fat. Experts state that visceral fat increases the risk of diabetes and heart disease.