title: Adiposity rebound is misclassified by BMI rebound.
abstract: OBJECTIVE
  Adiposity rebound (AR) is defined as the nadir or the inflexion point of body mass index (BMI) percentiles between the age of 3 and 7 years. An early rebound is seen as a risk of obesity and, thus, AR is considered as a suitable time period for prevention. As BMI does not reflect body composition, we aimed to examine the rebounds of fat mass index (FMI) and fat-free mass index (FFMI) together with BMI.
  
  
  METHODS
  Cross-sectional data of 19 264 children aged 3-11 years were pooled from three German studies (Kiel Obesity Prevention Study, the project 'Better diet. More exercise. KINDERLEICHT-REGIONS' and regular examinations of Jena children). Height and weight were measured. Fat mass (FM) and fat-free mass (FFM) were obtained from bioelectrical impedance analysis and analysed using a population-specific algorithm. Percentiles of BMI, FMI and FFMI were constructed by the LMS method.
  
  
  RESULTS
  Both BMI and FMI percentiles showed a rebound, whereas FFMI percentiles steadily increased with age. On P90, FMI rebound was about 1.6-1.8 years later compared with that of BMI, that is, at ages 4.2 years (BMI) and 5.8 years (FMI) in boys and at 4.2 years (BMI) and 6.0 years (FMI) in girls. At AR, the slope of the BMI-P90 was explained by increases in FFMI rather than FMI. By contrast, at FMI rebound, the slope of BMI was strongly related to FMI.
  
  
  CONCLUSIONS
  BMI rebound does not equal the rebound of FM. At AR, the slope in BMI is determined by the increase in FFMI. AR should be defined as FMI rebound rather than BMI rebound.
authors.affiliation: Institute of Human Nutrition and Food Science, Christian-Albrechts University, Kiel, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Plachta-Danielzik
authors.forename: A
authors.initials: A
authors.lastname: Bosy-Westphal
authors.forename: B
authors.initials: B
authors.lastname: Kehden
authors.forename: M I
authors.initials: MI
authors.lastname: Gehrke
authors.forename: K
authors.initials: K
authors.lastname: Kromeyer-Hauschild
authors.forename: M
authors.initials: M
authors.lastname: Grillenberger
authors.forename: C
authors.initials: C
authors.lastname: Willhöft
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
authors.forename: M J
authors.initials: MJ
authors.lastname: Müller
mesh_terms: D050154:Adiposity / Q000502:physiology*; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D009765:Obesity / Q000453:epidemiology*; D050177:Overweight / Q000453:epidemiology*; D015995:Prevalence; D015430:Weight Gain; D044465:White People