Everyone talks about needing a caloric deficit for fat loss, but is a caloric surplus needed to build muscle?

Not necessarily. This is because stored fat is stored energy. And that energy is available for the body to use as fuel for the muscle-building process.

That said, to date, there are several studies showing that, yes, you can simultaneously build muscle and lose fat. Research has demonstrated this in variety of populations:

• Overweight, sedentary adult males
• Older men and women
• Physically active healthy men
• Young women

But hold on. Get this part straight: Your body can't turn fat into muscle or vice versa. Fat is fat; muscle is muscle.

If you're overweight, your body can use your stored energy (fat) to fuel the muscle-building process when the needed calories to build muscle aren't coming from additional food intake.

So What's the Best Diet?

That depends on where you are now and what you're trying to accomplish. And whether you're in a caloric deficit or not, make sure it contains enough protein.

That's the main piece of diet advice if you're trying to build muscle. The standard rule of thumb is one gram of protein per pound of bodyweight.