What Changes After 40 and Why It Is Not Your Fault The frustration most women over 40 express is real and physiologically valid: the approach that worked in your 30s stops working, fat redistributes from hips and thighs to the abdomen, and the same calorie deficit that previously produced results now seems to do nothing. This is not a failure of willpower. It is a hormonal reality with specific biological mechanisms โ€” and specific solutions. Research shows that metabolic rate naturally declines by 2-4% per decade after age 30, but the decline accelerates significantly during perimenopause. โ€ฆ