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Super size me? Teens more susceptible to large portions than younger children, study

By Elaine Watson , 18-Oct-2011

Teenagers are more likely to overeat when presented with excessive amounts of food than young children because physiological cues telling them when they are hungry or full appear to exert less influence than environmental cues such as portion sizes, according to new research.

“Although the exact age at which children become susceptible to environmental exposures such as larger portions of foods remains unclear, our findings supported previous findings that suggested that young children might be better able to self-regulate their energy intakes than are older children,” argue Carmen Piernas and Dr Barry M Popkin in a paper published in the American Journal of Clinical Nutrition.

While some researchers argue children of all ages are predisposed to overeat, the data suggests that energy intakes in very young children are less affected by increased portion sizes than with older children, who progressively increase intakes when offered larger portions, claim Popkin - a professor of nutrition at the University of North Carolina-Chapel Hill, and Piernas - a doctoral student in nutrition epidemiology.

“In the context of the growing obesity in the United States, larger portion sizes of selected energy-dense, nutrient-poor foods have increased in parallel with energy intakes at meals, especially in adolescents and middle-aged children.”

Overeating, age and ethnicity

Besides age differences, add the authors, “another short-term design showed that larger portions promoted excess energy intakes in low-income Hispanic and African American children of five years of age.

“The percentage of kilocalories from pizza within a meal increased more sharply in non-Hispanic African Americans, in Hispanics, and in the group with a low household education than in the other groups.”

Increased energy intakes, reduced activity

Popkin and Piernas analyzed data from four nationally representative surveys from 1977 to 2006 and measured trends in portion sizes (calories, grams and milliliters) of selected foods (sugar-sweetened beverages, salty snacks, French fries, burgers, desserts, pizzas, and Mexican fast food), and energy intake (calories) at eating occasions during which these foods were consumed.

Trends were then reported by age group (2–6years, 7–12years, and 13–18years), sex, and socioeconomic status.

In 2003–2006, the selected foods accounted for 38% of daily energy intake in 13–18-year-olds, 35% in 7–12-year-olds, and 28% in 2–6-year-olds, they observed.

“To our knowledge, our study provided new insights about the behavioral and nutritional changes that have occurred over the past three decades in the United States, which may have contributed to increased daily energy intakes during a period of reduced activity and increased risk of childhood obesity.”

Mindless eating

Speaking at the American Dietetic Association conference last month, Dr Brian Wansink – Dyson Professor of Consumer Behavior at Cornell University and author of ‘Mindless Eating: Why We Eat More Than We Think’ - told delegates appropriate portion sizes were key to tackling over eating, adding: “We eat with our eyes not with our stomachs.”

Even young children had a tendency to overeat if portion sizes were not controlled, he said, citing a recent study at Cornell University in which children aged three to six were told they were participating in a TV viewing study and given unlimited access to one of four snacks as they watched (raw veggies, veggies and cheese, chips and crackers, and pre-wrapped cheese).

Those given chips and crackers wolfed down on average 621 calories– a third of their daily requirement - in one sitting, he said.

“If you’re given a bottomless bowl of food, you will always eat more.”

Source: American Journal of Clinical Nutrition, September 2011

“Increased portion sizes from energy-dense foods affect total energy intake at eating occasions in US children and adolescents: patterns and trends by age group and socio-demographic characteristics, 1977–2006”

Authors: Carmen Piernas and Barry M Popkin

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