On the question of age and weight loss...
It has been suggested that one of the major reasons our resting metabolism
slows as we age is because as we age we tend to lose muscle mass.
This can of course be reversed or minimized by doing weight bearing exercises to build or maintain the size and strength of our muscles.
It also helps keep our bones strong, which also tend to get weaker and more brittle with age often leading to osteoporosis.
So while there is some evidence that it is harder to lose weight as we age, the point made earlier that there is no excuse is still very valid.
Exercise, including weight bearing exercise like walking, weight training etc are vital to maintaining or building strong muscles that burn extra calories/kilojoules at work, rest and play!