When rats eat less food for several months, their testosterone levels go up compared to rats that eat normally.

Researchers found that when they put middle-aged male rats on a diet with 15% or 35% fewer calories, it helped their reproductive health at first. But after a year on the diet, these benefits went away, and only one-third of the dieting rats still showed normal mating behavior compared to all of them at six months.

Eating less food for six months helped older male rats have better sex lives by making them mount and mate faster and ejaculate more often, compared to rats that could eat as much as they wanted.

When older male rats eat less food for several months, their bodies process sugar better and have healthier hormone levels.

Eating less food for six months helped older male rats have better swimming sperm, and this improvement lasted for a year compared to rats that ate normally.