In new research to be presented at this year’s European Congress on Obesity in Istanbul, Turkey (12-15 May) and published in The Journal of Nutrition, a 42-year old theory as to why children’s body mass index (BMI) decreases post-infancy before then rising continuously from age six years –’the adiposity rebound’ is refuted using new analyses – rather than decreasing body fat, the real reason is proposed as increasing muscle mass.