One of the primary reasons losing weight is harder to do as you grow older is due to a slowing metabolism. It is estimated that your metabolism slows down 5% every decade after you turn 40. This can occur because of the loss of muscle (or sarcopenia) which plays a crucial part in maintaining your metabolism.
It’s not a myth that weight loss gets harder as you get older. Women who have children later in life might have a harder time shedding the pregnancy weight. However, even people trying to lose just a few pounds will have a harder time at 40 years of age than they did at 20. As the body changes, so too should your weight loss system.
As people age, their hormones change, which causes their metabolic rate to change.
As men lose testosterone and women lose estrogen, their metabolism slows, making the weight easier to put on and harder to take off.
Weight management can become more difficult for people in their 20s, but weight loss can become even trickier in your 30s.