Biological fact: our metabolism slows down as we get older, in both men and women. For women, this is accelerated by menopause. Can someone who had a normal weight in their twenties and thirties stay at that weight through middle and old age their life? Yes, but they will have to eat fewer calories and intensify their workout (some will find it easier than others). People who keep eating the same amount of food and don't exercise enough will gain 20 - 30 pounds over a couple of decades. But for someone to gain 80 pounds in a short period of time - something is wrong.