The contribution of fat and fat-free tissue to body mass index in contemporary children and the reference child

Wells, Jonathan C. K.; Coward, W. A.; Cole, TJ; Davies, P. S. W.

doi:10.1038/sj.ijo.0802077

Cited by 116 publications

(83 citation statements)

References 26 publications

(30 reference statements)

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“…Such a hypothesis is not supported by recent evaluations of children's body composition, which showed that contemporary children in general have lower levels of LM than in previous generations. 32 Thus, increases in fatness, especially central fatness, 33 appear to precede the increases in LM that occur in childhood obesity, with much of the apparent increase in LM attributable to increased height, and to changes in hydration and mineral mass that follow increases in weight. 31 It is possible therefore that our finding that early rapid growth was associated with BMI, but not with fatness, may be due to two issues: first, variability in LM may adversely influence the categorisation of obesity; second, diet and activity levels may mediate possible relationships between early hormonal programming and later fatness.…”

Section: Discussionmentioning

confidence: 99%

Fetal, infant and childhood growth: relationships with body composition in Brazilian boys aged 9 years

et al. 2005

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BACKGROUND: Early growth rate has been linked to later obesity categorised by body mass index (BMI), but the development of body composition has rarely been studied. METHODS: We tested the hypotheses that (1) birthweight and weight gain in (2) infancy or (3) childhood are associated with later body composition, in 172 Brazilian boys followed longitudinally since birth. Growth was assessed using measurements of weight and height at birth, 6 months, and 1 and 4 y. Measurements at 9 y comprised height, weight and body composition using foot-foot impedance. RESULTS: Birthweight was associated with later height and lean mass (LM), but not fatness. Weight gain 0-6 months was associated with later height and LM, and with obesity prevalence according to BMI, but not with fatness. Weight gain 1-4 y was associated with later fatness and LM. Weight gain 4-9 y was strongly associated with fatness but not LM. Early growth rate did not correlate positively with subsequent growth rate. CONCLUSIONS: Early rapid weight gain increased the risk of later obesity, but not through a direct effect on fatness. Childhood weight gain remained the dominant risk factor for later obesity. The reported link between early growth and later obesity may be due partly to hormonal programming, and partly to the contribution of LM to obesity indices based on weight and height. Whether our findings apply to other populations requires further research.

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Section: Discussionmentioning

confidence: 99%

Fetal, infant and childhood growth: relationships with body composition in Brazilian boys aged 9 years

et al. 2005

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“…[36][37][38] The addition of circumferential measures may help to address the major weakness of BMI: its inability to distinguish between elevated adiposity and elevated lean mass. From a public health perspective, the observation that BMI in children and adolescents A Must and SE Anderson from 1987 to B1997 waist circumferences of British children increased more than BMI 33 suggests that surveillance by BMI alone may obscure important changes in body composition 39 at the population level. Prospective studies that demonstrate that the addition of an indirect measure of central adiposity is more tightly linked to obesity-related health consequences than use of BMI-for-age alone would provide some of the justification needed to add further complexity to research applications and to weight-screening recommendations.…”

Section: Looking To the Futurementioning

confidence: 99%

Body mass index in children and adolescents: considerations for population-based applications

2006

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After several years of experience with body mass index (BMI)-for-age reference standards in the US, the UK, and elsewhere, reflection on 'how things are going' seems timely. In this issue, Reilly 1 offers a summary of the evidence base for the diagnostic accuracy of BMI in youth and his perspective on what is achieved by a definition of overweight and obesity based on high BMI. To complement this, in our short review, we describe the BMI measure itself, the utility of a BMI z-score (s.d. score), their utility in cross-sectional and longitudinal applications in public health/surveillance, clinical and population-based research settings. Body mass index definedBody mass index is a measure of weight adjusted for height. It is calculated as weight in kilograms divided by the square of height in meters. Although BMI is an imperfect tool -it does not distinguish overweight due to excess fat mass from overweight due to excess lean mass -it is the most commonly used measure for assessing obesity in adults. Other methods of determining adiposity are more accurate, 2 but have limited applicability to screening or studying large populations. The BMI is well correlated with these more direct fatness measures, 3,4 and weight and height are simple, inexpensive, non-invasive measurements that are recorded routinely in clinical and research settings.Others have discussed the limitations of clinical screening for high adiposity by comparing weight centiles to height centiles, 5 and the inaccuracy of assessing overweight by observation or 'eye-balling' has been established. 6,7 Therefore, for screening or for epidemiologic research, using a weight/height index to define obesity has advantages that outweigh its limitations. Despite the likelihood of misclassification of the small percentage of individuals whose high BMI is due to lean muscle mass (e.g. some professional athletes), the great majority of individuals with high BMI have excess body fat. Use of body mass index in children and adolescentsThe BMI is used to assess weight status in children and adolescents as well as adults, but whereas in adults the BMI cut points that define obesity and overweight are not linked to age and do not differ for males and females, in growing children BMI varies with age and sex. Thus, a 5-year-old boy with a BMI of 20 kg/m 2 is likely to be overfat, but a 15-yearold boy with a BMI of 20 kg/m 2 is likely to be lean. As a result, for BMI to be meaningful in children it must be compared to a reference-standard that accounts for child age and sex.

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“…14 This approach of normalising outcomes for height rather than body mass represents a more informative way to compare individuals for the two tissue masses that comprise WT, and helps understand many aspects of body composition and its development over time. 15 It is of particular value in epidemiological studies, where variables such as physical activity may impose independent antagonistic effects on FM and FFM.…”

Section: Introductionmentioning

confidence: 99%

Indices of whole-body and central adiposity for evaluating the metabolic load of obesity

Wells

Victora

2005

Int J Obes

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BACKGROUND:To assess the relative metabolic load or risk imposed by fatness, fat mass (FM) is commonly expressed as a proportion of weight (% fat), while central adiposity is assessed using the ratio of triceps (TRI) to subscapular (SUBS) skinfolds. The statistical validity of these indices, defined as independence of the index from its denominator, has received inadequate evaluation. OBJECTIVE: To critically examine commonly used obesity indices, and to propose more appropriate approaches. DESIGN: Cross-sectional studies. SUBJECTS: In total, 148 infants; 2195 adult men aged 18 y. METHODS: log-log regression analysis was used to explore the relationships between FM and weight (WT) or fat-free mass (FFM) (adults), and between TRI and SUBS (infants and adults). RESULTS: The simple indices FM/WT, FM/FFM, TRI/SUBS and SUBS/TRI remained related to their denominators, showing their rankings of individuals to be biased by size or fatness. The appropriate power (p) by which to raise the denominator was determined from regression analyses, and differed from unity in all cases. Both skinfold ratios showed a nonlinear relationship with their denominators. CONCLUSION: Simple indices for evaluating whole-body or central adiposity are statistically flawed, and remain influenced by size or fatness of the subject. The index FM/WT is conceptually flawed because FM appears in both numerator and denominator, and the index FM/FFM p is preferable. Skinfold ratios are also problematic, and to evaluate central adiposity SUBS alone, or SUBS/ FFM p , may represent more appropriate approaches. These issues should be investigated in other studies in order to address possible influences of age, ethnicity, gender and nutritional status.

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The contribution of fat and fat-free tissue to body mass index in contemporary children and the reference child

Cited by 116 publications

References 26 publications

Fetal, infant and childhood growth: relationships with body composition in Brazilian boys aged 9 years

Fetal, infant and childhood growth: relationships with body composition in Brazilian boys aged 9 years

Body mass index in children and adolescents: considerations for population-based applications

Indices of whole-body and central adiposity for evaluating the metabolic load of obesity

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