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.
Instead, it comes down to a simple but changeable truth: As we get older, we get less and less active.