Designing Health & Fitness Apps with the Mind in Mind - Massimo Ingegno (and other speakers)

In this randomized clinical trial of 602 overweight and obese adults from 40 states across the United States, gamification interventions with support, collaboration, and competition significantly increased physical activity compared with the control group during the 24-week intervention. The competition arm had the greatest increase in physical activity from baseline during the intervention; during the 12-week follow-up, physical activity was lower in all arms, but remained significantly greater in the competition arm than in the control arm.

In a meta-analysis of real-life experiments drawn from food science, nutrition, health economics, marketing and psychology, the authors find that behavioural nudges - facilitating action rather than providing knowledge or inducing feelings - can reduce daily energy intake by up to 209 kcal, the same number of calories as in 21 cubes of sugar.

If you want a child to eat more vegetables, it might help to use plates illustrated with pictures of vegetables.