The following is an excerpt from an article written by Madelyn Fernstrom. It was originally published on www.today.com.
Why is weight gain so much easier after 40?
Metabolic rate slows by about 5 percent every decade
Translated into calories, this means most women by age 50 need to consume about 200 calories less every day compared to calories eaten at age 30, just to maintain the current weight. And while exercise can contribute to weight maintenance, eating too many calories is the main reason for weight gain.
While hormonal changes do not directly trigger weight gain, it becomes easier to gain weight with an altered hormone profile. Declining estrogen along with increasing cortisol levels (a response to dropping estrogen levels along with increasing stress) can both contribute to fat distribution in the body— even without weight change. Elevated cortisol levels can also shift where fat goes — to the middle — even without a change in weight.
Muscle mass decreases with age, while fat increases
Contrary to popular belief, muscle does not “turn into” fat. This comes from eating too much, and not exercising enough. Losing muscle mass decreases how well your body uses calories, making weight gain easier.
Related: 8 Diet Changes for Women Over 40