Calorie dense foods promote weight gain but not satiety

Big portions encourage people to eat more but big portions of calorie dense food - the kind people tend to grab on the run - boost calorie consumption even higher without providing additional satisfaction, suggests a new study from Penn State University, US.

The study, said to be the first to focus on the combined effects of both portion size and calorie density or the calories per ounce, showed that calorie density and portion size add together to affect caloric intake.

Tanja Kral​, a doctoral candidate in nutritional sciences who conducted the study as part of her dissertation, reported that, "even though the study participants consumed 221 fewer calories when offered a smaller meal of lower calorie density, they felt just as full and satisfied as when they had consumed a larger meal of higher calorie density."​

Kral's dissertation adviser Dr. Barbara Rolls, who holds the Guthrie Chair of Nutrition in Penn State​'s College of Health and Human Development commented: "The fact that the participants in this study didn't notice when they were given lower calorie density food offers evidence that the food industry could change their products to make them healthier without causing customer dissatisfaction."​

She added: "Small reductions in the calorie density of foods will allow people to eat satisfying portions without consuming too many calories which, in turn, may help them with weight management."​

In the study, 39 normal weight and overweight women ate breakfast, lunch and dinner once a week for six weeks in Penn State's Laboratory for the Study of Human Ingestive Behavior. The breakfasts and dinners were standardised but the main entree at lunch was formulated to vary in calorie density as well as portion size.

The lunch entree was a pasta bake made from medium shells, zucchini, broccoli, carrots, onions, tomato sauce and parmesan, mozzarella and ricotta cheese. The calorie density was changed by varying the proportions of ingredients. The amount served was also varied from two cups to two and three-quarters cups to three and a half cups.

According to Kral, portion size alone increased calorie intake by 20 per cent, while calorie density alone increased intake by 26 per cent. Taken together portion size and calorie density increased calorie intake by 56 per cent.

Rolls​ noted: "In practical terms, the study shows that big portions of high calorie foods put people at greater risk of overeating than big portions alone."​ She suggested that people who like big portions should stick to water-rich foods that don't have too much fat. According to Rolls, other research in the laboratory has shown that big portions of a low-calorie salad as a first course can help lower the total amount of calories people consume.

Kral presented her results in a paper, 'The Combined Effects of Energy Density and Portion Size on Food and Energy Intake in Women', on Monday 13 October 2003 at the annual meeting of the North American Association for the Study of Obesity in Fort Lauderdale, Florida in the US.

The study was supported by a grant from the National Institute of Diabetes, Digestive and Kidney Diseases.