Preventing weight gain with calorie-labeling.

Abstract

Calorie-labeling has been suggested as an anti-obesity measure but there is no evidence for its effect, to date. Early adulthood is a critical life-cycle period for unwanted weight gain and obesity development. This study examined whether providing calorie information would help young adults to avoid weight gain. Using a pragmatic interrupted time-series study design, weight changes over 36 weeks were reported among two year-groups, each of 120 young adults, similar in age, gender, and ethnicity, living in fully-catered accommodation. Year 1: subjects were observed without calorie-labeling, apart from a 5-week pilot. Year 2: calorie-labeling was present prominently and consistently at main meals for 30 of the 36 weeks. Mean weight changes over 36 weeks, per protocol, were +3.5 kg (95% CI = 2.8-4.1 kg) (n = 64) in Year 1 and -0.15 kg (95% CI = -0.7-0.3 kg) (n = 87) in Year 2. Weight changes were significantly different between years, for males and females (both P < 0.001). Intention-to-treat analysis showed similar results. Relative Risk for weight gain in Year 2, compared to Year 1, was 0.5 (P < 0·0001). Calorie-labeling was associated with a 3.5 kg less weight gain, representing a low-cost "nudging" approach to combat the rapid weight gain seen in young adults.