The biggest reason you gain weight as you age has nothing to do with your metabolism

You've probably heard that once you hit 40, it's all downhill when it comes to your weight.

That inexplicable force we call our metabolism does begin to grind a bit slower every year from age 30 onward.

Here's the good news: The rate at which your metabolism slows down is actually rather minimal. In reality, most weight gain that happens in midlife isn't the result of a slower metabolism at all.