India, Sept. 7 -- Your skinny best friend seems to eat twice as much as you. But you're still overweight. Why? For decades, experts thought they had the answer - too many calories and not enough exercise. But the latest scientific research is turning those assumptions down. Differences in our individual biology - our genetics, hormones or psychology - all play a crucial role.

The show Why Do I Put on Weight follows five volunteers who go on diets tailored to their bodies and brains. They're just like us, normal people who experience weight gains and losses. Combining science with engaging personal stories, this experiment might change the way you think about diet. If you thought long term weight loss was impossible, you need to rethink....