Portion sizes of prepared foods to fight obesity?

Obesity, the bane of modern society, now affects some 200 million adults across the EU who may be overweight or obese.

And the number of European kids overweight is rising by a hefty 400,000 a year, according to data from the International Obesity Task Force (IOFT).

A key concern for governments footing the healthcare bills is that obesity, defined as a Body Mass Index over 30, is a risk factor for a host of (expensive) illnesses including heart disease, hypertension and respiratory disease.

According to the European Commission, obesity accounts for between 2 to 8 per cent of healthcare costs in Europe.

The recent study by food science researchers at the University of Illinois at Urbana-Champaign in the US suggests, perhaps not surprisingly because the food quantity is no longer in the hands of the consumer, that automatic portion size could have a significant impact on weight loss.

Researchers investigated how two diet regimens resulted in weight loss in overweight and obese men. Subjects following the first of the diets ate a self-selected diet based on the US food guide pyramid, a nutrition plan established by the US Department of Agriculture in 1992.

Subjects following the second diet ate two packaged entrees each day, plus recommended servings from the food pyramid.

Both diets contained about 1,700 daily calories with equal amounts of carbohydrates, protein and fat.

Participants in the packaged-entree group chose from 24 varieties of Uncle Ben's bowls, a brand of frozen entrees produced by Masterfoods USA.

Prior to the study, subjects in both diet groups reported daily consumption of about 2,400 calories and weighed about 97 kilograms with a body mass index (BMI) ranging from 26 to 42 kilogram per metre squared, which qualified them as overweight to obese.

"Subjects who followed the frozen-entree diet lost more weight (7.4 kg) compared with the subjects who made their own meals following the food pyramid (5.1 kg),"​ report the researchers in this month's Diabetes, Obesity and Metabolism​ journal.

Further, the average BMI decrease was one unit greater in subjects following the frozen-entree diet than subjects following the food-pyramid diet.

Research dietitians Sandra M. Hannum and LeaAnn Carson, who work in the laboratory of food science and human nutrition professor John W. Erdman, attributed the greater weight loss among the frozen-entree eaters to the automatic portion control built into that diet, whereas subjects following the pyramid diet had to make their own meals.

"The pyramid group had to figure out what to eat, and estimate how much they actually consumed,"​ says Hannum. "There was much more room for error."​

After the Illinois studies had finished, the USDA announced a new food pyramid, which allows people to customise their diets according to their age, gender and daily levels of physical activity. The greater complexity of the new pyramid may make this diet even more difficult for people to use, added Hannum.

These latest findings will further fuel consumer groups who are putting increasing pressure on the food industry, particularly in the US, to place limits on the portion sizes.

Firms are starting to react. US giant PepsiCo recently announced measures to cut sizes in US schools, saying it would limited serving sizes for all snacks to 150 calories, rising to 300 calories in middle schools.