But apparently, we can't get enough of these hefty helpings, which may explain why most Americans are consuming about 200 more calories each day than just a decade ago. In the average woman, 200 more daily calories than her body needs could lead to more than a pound of weight gain each month.
Just two months ago, Penn State scientists reported in the American Journal of Clinical Nutritionthat most of the 51 normal and overweight people they studied couldn't judge an "appropriate" portion and continued to eat when given more food on their plate.
"The more you give them, the more they will eat," lead researcher Barbara Rolls, PhD, tells WebMD. "But it's not a plate-cleaning phenomenon; it's more subtle than that. The people we studied were not even aware that their portions had changed, although we doubled them in some cases. And they ended up with the same fullness, even when they ate more food. It is almost as though they adjusted their reaction to hunger and fullness."
None of this surprises American Dietetic Association spokesman Keith Ayoob, EdD, RD, dietitian at Albert Einstein College of Medicine. But it does worry him.
"Obesity is a disease of excess -- it doesn't matter if the excess comes from McDonald's or olive oil or skinless chicken breasts," he says. "It does seem easier to have those excesses in high-calorie foods than in carrots and broccoli. But it's not just fast-food chains that are supersizing everything. It's everywhere. So my take-home advice is take it home. Because if you eat out, at most places you're getting twice as much food as you should be eating."
And at home, where most people consume about 55% of their meals? Read the labels, count calories and don't use those big plates like most restaurants. "Obesity is a family issue, and today's obese kids learn their eating habits at home," Ayoob tells WebMD. "In fact, I read of one study that the rate of obesity in humans in now paralleling to the rate of obesity in their housepets. And you can't blame the dog's obesity on a genetic link."