Bread
Potatoes
Rice
Pasta
Oatmeal
Quinoa

Those are examples of grains, also known as Carbs. Any meal or snack high in carbohydrates generates a rapid rise in blood glucose. To adjust for this rise, the pancreas secretes the hormone insulin into the bloodstream, which lowers the glucose. Insulin is, though, essentially a storage hormone, evolved over those millions of years of humans prior to the agricultural age, to store the excess calories from carbohydrates in the form of fat in case of famine.

Insulin, stimulated by the excess carbohydrates in our overabundant consumption of grains, starches and sweets, is responsible for all those bulging stomachs and fat rolls in thighs and chins.

Even worse, high insulin levels suppress two other important hormones -- glucagons and growth hormones -- that are responsible for burning fat and sugar and promoting muscle development, respectively. So insulin from excess carbohydrates promotes fat, and then wards off the body's ability to lose that fat.