Too much food and a lack of exercise are not the only factors contributing to obesity. Scientists reviewed more than 100 studies and identified 10 other possibilities as to why Americans are heavier than ever before.

1. Less sleep.
We’ve gone from an average of nine down to about to seven hours of sleep a night; sleep deprivation is linked to a more robust appetite. And of course, if you are awake, you have that many more hours to fall prey to mindless eating.

2. Pesticides, Bovine Growth Hormone, and other chemicals in foods.
These substances can change hormonal activity, which can boost body fat.

3. Air conditioning and heating.
We don’t sweat and shiver as much as our ancestors, so we don’t burn as many calories.

4. Fewer smokers.
Nicotine is an appetite suppressant.

5. Greater use of medications.
Medications such as antidepressants and diabetes drugs, which have weight gain as a potential side effect. This also highlights just what a problem diabetes has become in this country.