McKayla Maroney is eating a high Carbo-raider type diet.
Timeline of the biology of her weight gain
2012 Pushing body too much for Olympics
2013 With McKayla able to eat more, her body is able to protect itself by storing energy (fat)
2014 McKayla searching for diets, finds the high-carb vegan community
How I eat - https://www.youtube.com/watch?v=EFcesyOsAgE