Unnatural chemicals in the food are making us fat.

The new weight-gain threat
Obesogens are chemicals that disrupt the function of hormonal systems; many researchers believe they lead to weight gain and, in turn, numerous diseases that curse the American populace. They enter our bodies from a variety of sources — natural hormones found in soy products, hormones administered to animals, plastics in some food and drink packaging, ingredients added to processed foods, and pesticides sprayed on produce. They act in a variety of ways: by mimicking human hormones such as estrogen, by misprogramming stem cells to become fat cells and, researchers think, by altering the function of genes.