11 fitness 'truths' that are doing more harm than good

Whether you want to tone up, slim down, or give yourself a mood boost, you've likely taken a stab at tweaking your fitness routine.

Unfortunately, there's a lot of "fitness" advice out there that won't help you meet your goals and could actually be doing you more harm than good.

For example, which matters more for weight loss: exercise or diet?

Are marathons the best way to get fit?

The answers to these questions might surprise you.