Low metabolic rate

Also known as a slow metabolism or low BMR, which is the rate in which your body turns calories into energy. 

Metabolism means all of the chemical  processes that go on consistently inside the body to keep you alive and your organs working regularly, for example, breathing, repairing cells and processing nourishment. These synthetic procedures require energy. The base measure of energy your body requires to do these concoction forms is known as the basal metabolic rate (BMR).

Body size, age, genes and gender all assume a part in deciding your metabolic rate. Muscle cells require more energy to keep up than fat cells, so individuals with a higher muscle to fat proportion have a tendency to have a higher BMR. As we age, we tend to increase fat and lose muscle. This clarifies why the BMR tends to diminish with age.