Dr. Ian Smith explains how bodies can achieve 'metabolic flexibility' to turn fat into fuel

CHICAGO (WLS) -- The human body has the amazing ability to switch which fuels it uses for energy based on what fuel is available at the time.

Researchers call this metabolic flexibility.

Bodies that are able to make this switch can burn sugars, proteins and other food nutrients when available, and then switch to burning the body's fat storage or fatty acids when food calories are not available.

It turns out that losing weight is not just about burning calories. It's also about switching between these pathways as efficiently as possible.

Dr. Ian Smith, author of "The Met Flex Diet," explained to ABC7 how to train your body to make the switch.