Stubborn Fats

Why is it that when you are older, the pounds are much harder to lose?  Diet and exercise alone don't seem to work, to think that I have been working out for an hour a day now.  It's been a month and all I managed to shed off are two pounds.  :(  I have tried taking diet pills back then, and I'm considering taking them again.  This time though, I'd like to have supervision so I'm going to ask my doc for advice.  I am not getting any younger and I'm not as adventurous as when I was 10 years ago.