THE EFFECT OF VARYING THE PORTION SIZE AND ENERGY DENSITY OF FOODS AND MILK ON PRESCHOOL CHILDREN’S INTAKE

Open Access
Author:
Kling, Samantha May
Graduate Program:
Nutritional Sciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 24, 2016
Committee Members:
  • Barbara J. Rolls, Dissertation Advisor
  • Barbara J. Rolls, Committee Chair
  • Penny M. Kris-Etherton, Committee Member
  • Kathleen L. Keller, Committee Member
  • Eric Loken, Outside Member
  • Tanja Kral, Outside Member
Keywords:
  • preschool children
  • milk
  • food
  • portion size
  • energy density
  • energy intake
  • eating behavior
  • obesity
Abstract:
Serving larger portion sizes and energy-dense foods and beverages has robust effects on preschool children’s intake, and these factors are often implicated as the primary drivers in the obesity epidemic. Experimental studies have shown that variations in portion size and energy density (ED) have substantial, independent effects on children’s energy intake. The available data demonstrate that continuing to serve large portions has effects that persist for up to 24-hours in children, and for ED, the effects continue for up to 2 days. Since children are exposed to large portions of higher-ED foods, it is essential to investigate how these factors combine to influence preschool children’s intake, but the studies that have been conducted report inconsistent results. Furthermore, in these studies the main dish at the meal was the only item varied by portion size and ED, which does not represent the current eating environment in which other foods and beverages also vary in these properties. For this dissertation, two studies were designed to test the effect of varying both the portion size and ED of an entire meal (Study 1) and of milk (Study 2) on preschool children’s intake. Investigation of these effects will aid in the development of strategies to counter these environmental food cues and moderate energy intake. In Study 1, the effect of varying the portion size and ED of a meal of commonly consumed foods on children’s intake was evaluated. In a crossover design, lunch was served in 3 childcare centers once a week for 6 weeks to 120 children aged 3-5 years (14% overweight or obese). For the 6 meals, all items were served at 3 levels of portion size (100, 150, or 200%) and 2 levels of ED (100 or 142%). Lunch items were either lower- or higher-ED commercially available versions of chicken, macaroni and cheese, vegetable, applesauce, ketchup, and milk. Children’s ratings of the foods showed that the lower-ED and higher-ED items were equally well liked. Varying the ED of food and milk did not affect the total weight consumed across meals; however, serving larger portions significantly increased the weight eaten at both the lower- and higher-ED meals (P<0.0001). Meal energy intake was found to be independently affected by ED and portion size (both P<0.0001). Increasing meal ED by 42% led to a 40% increase in energy intake and doubling portions led to a 24% increase. These effects combined to increase intake by 177±12 kcal or 80% in the meal with the higher ED and largest portions compared to the lower-ED meal with the smallest portions. Large portions of high-ED foods are likely to contribute to childhood obesity by promoting the overconsumption of energy. Since the differences in ED did not affect ratings of liking, these results suggest that preschool children could be offered lower-ED versions of commonly consumed foods in order to moderate energy intake. In Study 2, the extent that changes in milk portion size and ED affected children’s intake of both milk and the accompanying foods was investigated with a 2-by-2 crossover design. Experimental meals were served once a week for 4 weeks in childcare classrooms and were consumed ad libitum by 125 children aged 3-5 y (8% overweight or obese). Across the 4 meals, unflavored milk was varied in portion size (9 fl. oz. or 6 fl.oz. [recommended]) and ED (3.25% full-fat [0.61 kcal/g] or 1% low-fat [0.42 kcal/g; recommended]). The foods served at the meal (chicken, pasta, broccoli, and bananas) were not varied. The results showed that serving the larger portion of milk increased milk energy intake by 20±3 kcal (27%; P<0.0001) compared to serving the smaller portion, but had no significant effect on food intake or meal energy intake. Serving higher-ED milk increased milk energy intake by 31±2 kcal (44%) and decreased food energy intake by 26±6 kcal (10%) compared to serving lower-ED milk (both P<0.0001). Thus, across all children, the change in milk ED did not influence total energy intake at the meal. The effects of milk portion size and ED were not influenced by most child characteristics, such as age, body size, and parent-reported eating behaviors; however, the effect of milk ED on intake did differ significantly by sex. For boys, serving higher-ED milk decreased food energy intake by 43±8 kcal (16%; P<0.0001) and did not affect total energy intake compared to serving lower-ED milk. For girls, consuming more energy from the higher-ED milk did not lead to a significant compensatory reduction in food energy intake and an additional 24±10 kcal (7%; P=0.03) was consumed over the entire meal. This suggests that boys, but not girls, adjusted their food energy intake in response to changes in ED of milk consumed with lunch. These results showed that serving larger portions of milk could promote milk intake without affecting total energy intake at a meal, but the effects of milk ED on total energy intake at a meal vary between children. The results of the two present studies indicate that the intake of preschool children is influenced by variations in both portion size and ED. When larger portions are served, children increase both the weight consumed and energy intake. However, when similar portions are served, they consume a consistent weight of a meal or milk even when ED is varied; therefore, when ED is increased children consume significantly more energy from the food or beverage. When the portion size and ED of all foods at a meal are manipulated, preschool children’s intake is substantially influenced; however, if only one item is manipulated, such as milk, some children may adjust intake to account for changes in these factors. For most children, however, strategies that moderate the portion size of food would be effective at reducing energy intake. Choosing lower-ED commercially available products, such as lower-fat milk, grilled chicken strips, and unsweetened applesauce that are similar in acceptability to the higher-ED versions is an effective and easy strategy for caregivers to adopt. Overall, the results of the present research indicate that the combination of large portions and higher-ED foods has a substantial effect on ad libitum energy intake, which indicates that policy makers and food producers should consider these factors when developing recommendations and products.