Objective: Examine the effect of weekday exposure over 6 months to different lunch sizes on energy intake and body weight in a free-living sample of working adults.
Methods: Adults (n = 233) were randomly assigned to one of three lunch size groups (400 kcal, 800 kcal, and 1,600 kcal) or to a no-free lunch control group for 6 months. Weight and energy intake were measured at baseline, and months 1, 3, and 6.
Results: Lunch energy was significantly higher in the 800 and 1,600 kcal groups compared with the 400 kcal group (P < 0.0001). Total energy was significantly higher for the 1,600 kcal group compared with the 400 and 800 kcal groups (P = 0.02). Body weight change at 6 months did not significantly differ at the 5% level by experimental group (1,600 kcal group: +1.1 kg (SD = 0.44); 800 kcal group: -0.1 kg (SD = 0.42); 400 kcal group: -0.1 kg (SD = 0.43); control group: 1.1 (SD = 0.42); P = 0.07). Weight gain over time was significant in the 1,600 kcal box lunch group (P < 0.05).
Conclusions: Weekday exposure for 6 months to a 1,600 kcal lunch caused significant increases in total energy intake and weight gain.
Copyright © 2014 The Obesity Society.