By lifting heavy weights, you are sending a signal to your body that you want to preserve your muscle mass, and that you only want to lose fat, not muscle.

He says this may explain why two individuals with similar eating and physical activity habits may have very different body weights-because their bodies process the food differently.

And while you may run, lift weights, or do yoga to keep your body in good condition, chances are you ignore your brain and trust it to do its job.