Everyone over 40 would agree that it is harder to lose weight than in their 20's. Despite this, I have clients in their 40's who are in the best shape of their lives. Being over 40 doesn't mean squat!
There are some factors in life that can be controlled, and others that can't. This list of 50 Reasons Why it's Harder to Lose Weight After 40 contain both.
Figure out what can be changed, come to terms with the things that cannot, and keep reaching goals!