Portion Sizes Eventually Lead to Weight Gain (cont.)

It All Adds Up

There's little doubt that portion sizes -- along with American waistlines -- have ballooned over the last several decades. In a study published in the American Journal of Public Health in 2002, Lisa R. Young, PHD, MD, and Marion Nestle, PhD, MPH write that "marketplace food portions are consistently larger than they were in the past as well as considerably larger than federal standard portion sizes. These observations suggest a need for greater attention to food portion size as a factor in energy intake [calorie] and weight management. A recent survey reports that Americans tend to ignore serving size when they are attempting to maintain body weight."

In an interview with WebMD, Nestle, professor and chair of the department of nutrition, Food Studies & Public Health at New York University, says that McDonald's is at least taking a step in the right direction.

"I think what happened over time was that people got accustomed to larger portions, and think that reductions in portions is cheating, and so a small reduction, like the one that McDonald's has in mind, is really not a bad idea," Nestle tells WebMD. "I do not think that people will just buy more to make up the difference -- that's never been the case. It's always been the case that people eat what's put in front of them, and the difference between 7 and 6.2 ounces is probably three potatoes, not very much. I don't think anybody will notice."

Studies have consistently shown that people who are served larger portions will eat larger portions, agrees Barbara Rolls, PhD, who has made a career out of studying how food and liquid intake relate to obesity, eating disorders, and aging. She and her colleagues have performed studies showing that people who are fed increasingly larger portions of food on successive days -- without being told that the portions have been super-sized -- tend to eat the entire larger portion.

But most of us aren't born overeaters, suggests Rolls, professor of nutrition at Penn State University in University Park, Pa. She conducted a study in which 3-year-old and 5-year-old children were given three different-sized portions of macaroni and cheese on different days. "In the young kids, portion size didn't affect how much they were eating, but by the time the kids are 5 years old, the bigger the portion, the more they eat," Rolls said at a recent Harvard School of Public Health symposium on the science of obesity.

Eating Patterns Start Early

Lictenstein notes that "there's a tremendous amount of data that eating patterns are developed relatively young, and that's why you tend to see this tracking, -- not always, but you frequently see this tracking -- of chubbier parents having chubbier kids, and in some cases there may be a genetic basis, but for a lot of it, it probably is environmental."

Rolls tells WebMD that getting people to change the amount or volume of food they eat is a challenge. "To get people who are used to these huge portions back in sync with what people should be eating is very difficult in adults, and that's why I think reducing the calorie density is a more workable solution."