Americans eat what is put in front of them, even if it is way too much.

In fact, adults and children -- even kids as young as 2 -- will keep on eating if they are served bigger portions, according to two new studies discussed at the annual meeting of the Obesity Society, an organization of weight-loss professionals.

This research adds to evidence that super-sized portions could be contributing to adult and child obesity.

In one study, researchers at Baylor College of Medicine in Houston fed dinner to 75 kids ages 2 to 9 on three occasions. The meal was designed to be appealing to them: macaroni and cheese, corn, applesauce, baby carrots, chocolate-chip cookies and milk.

The macaroni-and-cheese entrée was served three different ways: an age-appropriate portion on the dinner plates; twice as much of the entrée on the dinner plate; and twice as much made available in an individual serving dish instead of on the plate. Findings included:

*63% ate more when served more. *Normal-weight kids were as likely as overweight kids to eat more of the larger portion. *When served an age-appropriate amount, children ate about half (56%) of the entrée. *When the portion was doubled, the children ate an average of 29% more of the macaroni and cheese than when they were served the more appropriate amount. However, they ate slightly less of the other foods so that their calorie intake at the larger-entrée meal was only about 13% higher. This happened with all ages, even those as young as 2. *The kids who ate the most when the entrée was doubled ate less when allowed to spoon out macaroni from the individual serving dish.

"Serve small portions to small eaters and let kids participate in serving themselves," says Jennifer Orlet Fisher, an assistant professor in Baylor's pediatrics department. "Let young children take the lead in deciding how much to eat."

GROWN-UP OVEREATING Studies have shown that adults eat more when served larger portions over the course of a day or two. However, researchers wondered whether people would continue to overeat when served large portions for longer periods.

So Barbara Rolls, a nutrition professor at Pennsylvania State University, and colleagues had 23 normal-weight and overweight adults eat foods and beverages prepared in the university's nutrition lab for two 11-day periods.

Standard portions were served for one period. That amount was increased by 50% for the second period. The findings:

*Participants ate an average of 400 more calories a day when served the larger portions, for a total of 4,473 more calories over 11 days. In theory, that could be a 1-1/4-pound weight gain. *They ate more for the entire 11 days, even though they reported being less hungry and more full over that time. *When the portions increased, participants ate more of the entrées, snacks and side dishes but not more vegetables.

LOSING JUST A LITTLE Obese people who lose as little as 17 pounds likely will improve their cholesterol, blood pressure, blood sugar and other health-risk factors, says another study presented at the meeting.

"Modest weight loss improves nearly all parameters of health," says researcher Suzanne Phelan, an assistant professor of psychiatry and behavioral medicine at Brown University.

Phelan worked with researchers at the University of Pennsylvania in Philadelphia, where they recruited 180 women and 44 men who weighed an average of 235 pounds.

About 35% of the group had a condition called metabolic syndrome, which meant they had a minimum of three out of five health-risk factors. Those factors might include a high waist circumference (greater than 40 inches for men and greater than 35 inches for women); high blood pressure; low HDL, or good cholesterol; high triglycerides; or high fasting plasma glucose. A combination of these risk factors raises the risk of several life-threatening illnesses.

The participants received weight-loss therapies, including behavior modification and the diet drug sibutramine, which works on the brain chemistry to reduce hunger and enhance the feeling of fullness. After one year:

*Participants lost an average of 7.5% of their starting weight, or about 17 pounds. *The percentage of participants with metabolic syndrome dropped from 35% to 28%.