What would happen if a fast-food restaurant reduces the calories in a children's meal by 104 calories, mainly by decreasing the portion size of French fries? Would children compensate by choosing a more calorie dense entrée or beverage? Researchers at Cornell University, Dr. Brian Wansink and Dr. Andrew Hanks, analyzed transaction data from 30 representative McDonald's restaurants to answer that question.

Prior to 2012, the Happy Meal was served with one of three entrée options (chicken nuggets, cheeseburger, hamburger), a side item (apples or small size French fry), and a beverage (fountain beverage, white milk, , apple juice). By April 2012, all restaurants in this chain served a smaller size "kid fry" and a packet of apples with each CMB. Wansink and Hanks found that this change in default side offerings resulted 98 of the 104-calorie decrease in the CMB.

With such a large decrease in calories, would compensate by choosing a more calorie dense entrée or beverage? Wansink and Hanks found that 99% of children ordered the same entrée, and orders of chicken nuggets (the lowest calorie entrée) remained flat at nearly 62% of all orders. Yet, nearly 11% fewer children took caloric soda as a beverage and 22% more chose white or chocolate milk–a more satiating beverage. This increase was partially due to small changes in advertising for milk. Interestingly, the chocolate milk served in 2012 was of the fat-free variety compared to the 1% milk variety served previously. It also contained 40 fewer calories. Overall, the substitutions in beverage purchases resulted in 6 fewer calories served with the average CMB.

Small changes in the automatic—or default—foods offered or promoted in children's meals can reduce calorie intake and improve the overall nutrition from selected foods as long as there is still an indulgence. Importantly, balancing a meal with smaller portions of favored foods might avoid reactance and overeating. Just as managers have done this in restaurants, parents can do this at home.