The Effects of Portion Size on Food Intake

One potential method to promote fruit and vegetable (F&V) intake is to increase the portion size served at meals. While seemingly obvious, portion size effects can best be explained through an example. For instance, if a child normally eats 60g of a 75g portion, one might expect that child to eat the same amount even if the portion was doubled because the child was satisfied after eating 60g; however, a portion size effect is observed when that child eats 90g of the 150g portion. This intake promoting effect is well documented with energy dense entrées, but little is known about the potential of using larger portions to promote F&V intake.

Incorporating more vegetables into the main entrée¹ (pureed broccoli and cauliflower mixed into a tomato/cheese pasta sauce), or offering increased amounts of vegetables with a side of Ranch dressing prior to the meal² are potential methods to promote vegetable intake among preschool-aged children. In addition, doubling the portion sizes of applesauce, cooked plain broccoli, and carrot side dishes served along with a pasta entrée increased applesauce intake by 43% among 5- to 6-year-old children^3.

The influence of the quantity of fruit served on the consumption of vegetables

Increasing the broccoli portion size was only effective in promoting intake among children who preferred the broccoli over all other foods served at the meal. Though F&V are often served together at meals, it is well known that young children accept fruits more readily than vegetables. Based on these observations, the primary aim of this research was to determine if the amount of fruit served influences the effect of portion size on vegetable intake. A secondary aim was to determine if the amount a child increased their intake when larger portions were served was dependent on how much a child liked a particular fruit or vegetable.

Participants were 30 children (4-6 years of age) and their primary caregivers living in the greater metropolitan area of Philadelphia, PA. Once a week for four weeks, children ate dinner in groups of two to three children in a laboratory setting. The meal consisted of steamed broccoli with butter, and drained canned peaches that were served with fixed portions of pasta with sauce, a side dish of light Ranch dressing, and 2% milk. The amounts of broccoli and peaches were varied both separately and jointly between a reference portion (75g) and a large portion (150g) resulting in four conditions: (75g F; 75g V), (150g F; 75g V), (75g F; 150g V) and (150g F; 150g V). The order that the four meals were presented to each group of children was randomized. A trained staff member sat at the table during the meal and the children were given 20 minutes to eat dinner. To minimize visual comparisons of portion sizes, all children in the same group were served the same meal.

Increasing portion size, increased F&V intake

Children consumed 41g or 70% more fruit in the large portion conditions than in the reference conditions (59g vs. 101g) and 12g or 37% more of the vegetable side dish in the large portion conditions than in the reference conditions (32g vs. 44g). Increasing the portion size of fruit did not affect vegetable intake and vice versa. In addition, doubling the vegetable portion size increased vegetable intake even when larger portions of fruit were served.

A larger vegetable portion size effect was observed among children who rated the vegetable as tasting “yummy,” indicating that the degree of liking a vegetable influences the amount children will increase their intake when portion size is increased. Finally, given the concerns of the childhood obesity epidemic, total caloric intake at meals did not increase when F&V portion sizes were doubled.

Prerequisite: increase familiarity and acceptance of F&L

This study provides new evidence that increasing the portion sizes of F&V separately or jointly at meals can increase children’s intake of both types of healthful foods. Children who dislike F&V will be unlikely to increase their intake when served larger portions without being exposed to feeding environments and methods that increase their familiarity and acceptance of F&V. To the extent that such techniques are successful in promoting acceptance, serving larger F&V portions is one potential strategy to promote healthy eating habits in children.

BASED ON: Mathias KC, Rolls BJ, Birch LL, Kral TV, Hanna EL, Davey A, Fisher JO. Serving larger portions of fruits and vegetables together at dinner promotes intake of both foods among young children. J Acad Nutr Diet. 2012 Feb;112(2)266-70.