March 13, 2026Journal of Nutrition0 citationsOpen Access
Adiposity Rebound or Fat-Free Mass Anabolism in Children – Challenging a 42-Year-Old BMI puzzle with Waist-to-Height Ratio: The American Society of Nutrition Foundation’s 2025 Inaugural Flemming Quaade Award for Innovation in Childhood Obesity Lecture
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Key Result
In children, WHtR continued to decrease after BMI adiposity rebound at age 6, suggesting rebound is an epiphenomenon rather than a physiological norm.
Key Points
- The aim is to challenge the long-standing concept of adiposity rebound in early childhood and propose an alternative explanation involving fat-free mass anabolism.
- Analyzed data from 2410 children and adolescents aged 2–19 years from the NHANES 2021–2023 cycle.
- Compared traditional BMI measurements with waist circumference-to-height ratio (WHtR) as a more specific adiposity marker.
- Identified changes in body composition across critical developmental milestones from age 2 to 7 years.
- BMI showed a rebound by age 6 years, returning to mean values observed at age 2.
- WHtR values did not return to baseline throughout childhood, indicating a continuous decrease in fat mass.
- A body composition reset was noted at the intersection of BMI and WHtR trajectories during early childhood.
Structured PICO
P
Population
2,410 children and adolescents aged 2-19 years from the US National Health and Nutrition Examination Survey (NHANES) 2021-2023 cycle.
O
Outcome
Trajectories of body mass index (BMI) and waist circumference-to-height ratio (WHtR) across childhood and adolescencesurrogate
Waist-to-height ratio trajectories suggest that the widely accepted BMI-based 'adiposity rebound' in early childhood is an epiphenomenon likely driven by fat-free mass anabolism rather than true adiposity.
Main Result
Absolute Event Rate: 0% vs 0%
Abstract
Rolland-Cachera and colleagues introduced the concept of “adiposity rebound” in a paper published in the American Journal of Clinical Nutrition in 1984. They observed that body mass index (BMI)-increased during the first year of life and then decreased with a renewed rise at about 6 years of age, which they termed “adiposity rebound”, concluding that early rebound increased the risk of excess adiposity in later years. Although this concept has been vigorously criticised, an alternative explanation for this phenomenon has been lacking for 42 years. In this study, 2410 children and adolescents' data aged 2 – 19 years from the US National Health and Nutrition Examination Survey (NHANES) 2021–2023 cycle were analysed using a more accurate adiposity-specific marker, waist circumference-to-height ratio (WHtR). The mean value of BMI at age 2 years (17.1 kg/m 2 ) was regained by age 6 years after a significant decrease (adiposity rebound), but the WHtR mean value at age 2 years (0.54) was never regained throughout childhood and adolescence. While BMI-adiposity rebound seems to be completed by age 6 years, WHtR, which specifically assesses fat mass, continued decreasing. A body composition reset at the intersection of BMI and WHtR trajectories at age 4 years until WHtR nadir at age 7 years was observed. The body composition reset is a post-infancy BMI increase after an initial decline that simultaneously corresponds to a continued WHtR adiposity physiological decrease, culminating at the lowest WHtR trajectory before a subsequent WHtR increase. These novel findings establish that “adiposity rebound” is not physiologic but an epiphenomenon. I posit that “adiposity rebound” is a BMI-induced false discovery similar to the “obesity paradox” in adults. Therefore, fat-free mass or skeletal muscle mass anabolism is likely the accurate physiologic explanation for the body composition reset effect that occurs in early childhood.