Trajectories of Fat Mass Index, Fat Free–Mass Index, and Waist Circumference in Children

Abstract

Background Body composition and fat distribution change dramatically during adolescence. Data based on longitudinal studies to describe these changes are limited. The aim of this study was to describe age-related changes in fat free–mass index (FFMI) and fat mass index (FMI), which are components of BMI, and waist circumference (WC) in participants of Project HeartBeat!, a longitudinal study of children. Methods Anthropometric measurements and body composition data were obtained in a mixed longitudinal study of 678 children (49.1% female, 20.1% black), initially aged 8, 11, and 14 years, every 4 months for 4 years (1991–1995). Trajectories of change from ages 8 to 18 years were measured for FFMI, FMI, and WC. Because of the small number of observations for black participants, trajectories for this group were limited to ages 8.5–15 years. Results Body mass index, FFMI, and WC increased steadily with age for all race–gender cohorts. However, in nonblack girls, FFMI remained constant after about age 16 years. For black boys and girls, FFMI was similar at age 8.5 years but increased more steeply for black boys by age 15 years. In girls, FMI showed an upward trend until shortly after age 14 years, when it remained constant. In boys, FMI increased between age 8 years and age 10 years, and then decreased. Conclusions The extent to which each component of BMI contributes to the changes in BMI depends on the gender, race, and age of the individual. Healthcare providers need to be aware that children who show upward deviation of BMI or BMI percentiles may have increases in their lean body mass rather than in adiposity.

Tracking of body mass indices over 2 years in Māori and European children

“…Although BMI is a useful surrogate for body composition of a group, our data suggest in agreement with others that the relationship of BMI to body composition varies through childhood by age, sex (Demerath et al, 2006;Wright et al, 2010) and ethnicity (Eissa et al, 2009). What we add to the literature is the marked difference between the growth trajectories of Māori and European children.…”

“…A strength of the bioimpedance measurement was that the prediction equation was developed in Māori, Pacific and European children with a wide range of body fatness but it recognised that measurements of BF derived from bioimpedance measures are more applicable to group data rather than individual. We consider the sample size of this study to be insufficient to estimate the individual differences and the influence of other confounders, but, in agreement with other longitudinal studies, the main effects by gender, age (Demerath et al, 2006;Wright et al, 2010) and ethnicity (Eissa et al, 2009) on the relationship between BMI and BF are clear. Between 1991and 1995Eissa et al (2009 showed that black girls between age 10 and 12 years increased FMI by one unit, whereas the comparable change in our [2004][2005][2006] Māori girls was two units, which may be related to earlier puberty.…”

“…We consider the sample size of this study to be insufficient to estimate the individual differences and the influence of other confounders, but, in agreement with other longitudinal studies, the main effects by gender, age (Demerath et al, 2006;Wright et al, 2010) and ethnicity (Eissa et al, 2009) on the relationship between BMI and BF are clear. Between 1991and 1995Eissa et al (2009 showed that black girls between age 10 and 12 years increased FMI by one unit, whereas the comparable change in our [2004][2005][2006] Māori girls was two units, which may be related to earlier puberty. As in most studies, there is a potential bias of recruitment by differential dropout rates and self-selection because the children who were measured may have different characteristics to those who were not.…”

Body composition phenotypes in pathways to obesity and the metabolic syndrome

“…29 The use of this index, which is promising but requires a valid assessment of body composition by the pediatrician, is increasingly under evaluation. [30][31][32] Perspective Reference intervals of FMI versus FFMI, for adults, children and teenagers, can be used as indicative values for the evaluation of nutritional status (degree of overnutrition or undernutrition) of apparently healthy subjects. It can also provide complementary information to the classical expression of body composition reference values.…”

Age and gender-related fat mass index and fat- free mass index patterns among adolescents in Surulere LGA, Lagos

“…It is important to periodically survey populations at risk in order to determine the need for appropriate interventions. 2 Adolescence is one of the four known sensitive periods in life for the development of obesity, the other three being intrauterine life, infancy and ages 5 -7 years. 3 Often, body mass index (BMI) is used as proxy for assessing excessive accumulation of body fat, partly because of ease of measurement.…”