Company. "Humans are social animals. Our eating behavior is very sensitive to others in our environment." Simply watching someone else eat makes you want to eat. And of course, someone else is bound to take a bigger portion than you.
The researchers also blame the restaurant industry for much of our problem. Too many restaurants serve too much food, and of course it's often the wrong kind of food, heavy in fat and sometimes inexpensive. And Americans eat in restaurants far more often than they did just a few decades ago.
So what's a body to do? Monitor closely, the study concludes. Measure your serving size, and step on the bathroom scales every day. And as other studies have shown, don't leave candy on your desk day after day. Make fattening foods less accessible.
In their own experiments, the researchers found that just weighing yourself occasionally doesn't do much good, because normal body weight fluctuates on a daily basis, and obesity can result from very small and unnoticeable incremental gains over time.
They found that when college freshmen reported their weight to their nutrition department via email every day, they did not gain weight during their first semester -- a particularly dangerous period for students. But students who were not required to report their weight daily gained about a pound.
Thus close monitoring paid off. It may also be that simply reporting your weight to someone else every day is an intimidating reminder to watch what you eat.
The research is bound to be controversial. According to their own findings, most believe they can control what they eat by their own willpower. But one thing is clear: for many people, it isn't working.