The study, published in the June issue of Appetite (44:3, pp. 273-282), measured the total daily food intake of 16 preschool children in daycare over a seven day period. In the evenings and at the weekend their eating habits were documented in food diaries kept by parents or caregivers.
"We examined all the predictors we could of how much a child eats at a meal," said David Levitsky, professor of nutritional sciences and psychology at Cornell. "We found that portion size is, by far, the most important factor in predicting how much a child will eat."
Although the amount the children ate at mealtimes (snacks were considered as a meals) was negatively correlated with the amount and energy intake at the previous meal, so was the amount served. The children did not demonstrate an ability to adjust the amount consumed in response to the energy density of the meal, so the amount of calories eaten was directly related to the size of the meal.
"We also found that the more snacks children are offered, the greater their total daily food and calorie intake," added Levitsky.
Previous studies have suggested that children possess a much better instinctive ability to control their energy intake than adults. But the researchers in the current investigation said this observation could be attributable to conducting them in laboratories, rather than a natural setting where other factors come into play.
"The present results indicate that eating behavior of children is similar to adults in that they display very poor regulation of energy intake and are responsive to environmental stimuli," they wrote.
The revelation about children's portions comes at the same time as a study by food science researchers at the University of Illinois at Urbana-Champaign, which suggests that nutritious packaged foods could help consumers control portion size.
Automatic portion size could have a significant impact on weight loss, said the authors of that study. According to the National Institutes of Health, an estimated 16 percent of children and adolescents aged six to 19 are overweight - a 45 percent increase over figures obtained a decade ago.
The prevalence of type II diabetes, which usually develops in adulthood, is also increasing in children. One in four overweight children is said to be already showing early signs of the disease.
If children continue to be overweight or obese into adulthood, as is quite likely, they are at greater risk of developing life threatening cardiovascular disease such as heart disease, high blood pressure and stroke.
The worryingly high numbers of overweight and obese children reported from all over the Western world, prompting several governments to initiate publich health campaigns and the formation of the International Obesity Task Force.