Middle-age spread now has a medical name. It's called somatopause and it impacts 80 million baby boomers in the US. The spread is directly related to the decline of growth hormone produced by the body during aging.
Biomedical researchers have discovered that short-burst, sprinting type of exercises will increase the body's natural production of growth hormone. This type of exercise is highly productive, but to perform it safely you'll need to gradually build your time and intensity.