Why does weight loss seem to be harder as one ages?

Weight loss gets harder as someone ages for several reasons. One of the first things is the hormone changes that starts to take place. Weight can get more difficult as early as in your 20s, but it seems to particularly pickup in your 30s and as we get older. Men in particular seem to have that kind of fade-off as they hit their mid 50s, but women continue to typically gain weight until they are about 65 and then they tapper off. But as women lose estrogen and men lose testosterone, their metabolism rates change, they find that what they used to be able to do and not gain weight, suddenly they start to add on a few pounds. The loss of this lean muscle mass burns fewer calories also impacting their metabolic rates. So, it becomes a common problem in primary care that people come in complaining that I am not doing anything different than I have for years and yet I seem to just keep gaining weight, there must be something wrong.