As we age, a decrease in our physical abilities leads to a decrease in our metabolic rate (amount of energy used in a given period), which in turn contributes to weight gain. The physiological changes that accompany increasing age affect the body's composition and cardiopulmonary (heart and lung) function, thus reducing our ability to work and exercise and lose weight. Genetics, muscle mass, gender, calorie consumption versus expenditure, and lifestyle are all factors in weight gain.

Causes of middle-age weight gain and belly fat
Less muscle mass
The body’s muscle mass starts to shrink from the age of 30, leading to weight gain. Muscles burn more calories and keep your body lean.

Sedentary lifestyle
Many men and women tend to have a more sedentary lifestyle in their middle age. This further slows down the already declining metabolic rate

Lower metabolic rate
The body’s metabolic rate naturally slows down with age in both men and women. Burning less calories means gaining more kilos. You can boost your metabolism with regular exercise.

Stress
A high-pressure job means the body tends to be under continual stress. As the stress hormone cortisol sends messages to the brain to store up fuel to fight stress, you may end up eating more. The excess calories are stored as belly fat.

In other words, to escape the traps of unhealthy aging, it is imperative to look at the larger picture and pay close attention to all our actions. As we age, there is less and less room for compromise – or shall we say excuses. The best way is to start a health-promoting diet and lifestyle regimen as early as possible, and not deviate much from it, regardless how hard that may seem at times.

Another approach is to lose some weight with medication that help keep the weight off. There are numerous weight-loss remedies available over the counter such as Phentermine, Meridia or Xenical that can help accelerate your progress faster than you think.