Kool-Aid - and they weren't obese. And anyone who believes the government has it right - or not - on diets is delusional.
One big factor fueling the obesity epidemic could be this:
Tobacco is an anti-depressant; that's why people smoke. If they don't smoke, they eat, or take drugs, or drink. Ask any former smoker, or any current smoker who has tried to quit.
People who stay on high-protein (Atkins for example) diets for long periods, crave carbs. See research by Richard and Rachael Heller. Too much protein is as harmful as too much sugar.
There is no one-size-fits all diet. Listen to your body.