Diet Tip #18:
I think I weigh more with age, because there's so much more information stored in my head. Sooooo.... I'm definitely not overweight, I'm just extremely intelligent and once my brain was completely filled, it started settling down into the rest of my body. That's my story and I'm sticking to it. How about you?
Oh, you think you have a better one – it's your metabolism. Not. Most age-related weight gain has nothing to do with information storage or your metabolism. We put on pounds with age because we're less active. Don't fault your metabolism. I know this is not what you want to hear, but there are many things you can do to get fit, however eating spicy food, drinking lots of coffee or just getting a new gym membership are not among the good choices. You will definitely need to change your whole weigh of life... both food and fitness.
Business Insider's "The biggest reason you gain weight as you age has nothing to do with your metabolism" article will lay it all out for you.