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Ethnic differences in the accumulation of fat and lean mass in late gestation
Michelle Lampl1, Wesley Lee, Winston Koo
1Department of Anthropology, Emory University, Atlanta, Georgia, USA. mlampl@emory.edu
Insights
African American newborns have less lean mass and similar fat mass by 36 weeks gestation compared to Caucasian newborns. Fat accumulation is slower in African American fetuses later in gestation, potentially impacting later health outcomes.
Area of Science:
- Neonatal development
- Body composition
- Ethnic disparities in health
Background:
- Lower birth weight is linked to adult chronic diseases.
- Ethnic variations in birth weight may indicate differing tissue development patterns.
- Understanding neonatal body composition across ethnicities is crucial for predicting long-term health.
Purpose of the Study:
- To investigate neonatal body composition differences between non-Hispanic Caucasians and African Americans.
- To analyze fetal growth patterns in late gestation concerning body composition.
- To explore potential links between ethnic fetal growth strategies and later health disparities.
Main Methods:
- Air displacement plethysmography used to measure fat and lean body mass.
- Study included 220 non-Hispanic Caucasian and 93 non-Hispanic African American neonates.
- Linear regression analysis compared body composition between ethnic groups.
Main Results:
- At 36 weeks gestation, Caucasian neonates had significantly more lean mass (2,515g vs. 2,319g) but similar fat mass compared to African American neonates.
- By 41 weeks gestation, Caucasians had greater lean mass (319g heavier) and fat mass (123g heavier).
- Fat mass accumulation rate was 5.8 times greater in Caucasian fetuses (41.0 g/week) than in African American fetuses (7.0 g/week) during late gestation.
Conclusions:
- African American fetuses exhibit less lean mass and comparable fat mass by 36 weeks gestation.
- While lean mass accrual is similar later in gestation, African American fetuses accumulate fat at a slower rate.
- Divergent fetal growth strategies in body composition may underlie ethnic health disparities observed in adulthood.
Objectives:
Lower birth weight within the normal range predicts adult chronic diseases, but the same birth weight in different ethnic groups may reflect different patterns of tissue development. Neonatal body composition was investigated among non-Hispanic Caucasians and African Americans, taking advantage of variability in gestational duration to understand growth during late gestation.
Methods:
Air displacement plethysmography assessed fat and lean body mass among 220 non-Hispanic Caucasian and 93 non-Hispanic African American neonates. The two ethnic groups were compared using linear regression.
Results:
At 36 weeks of gestation, the average lean mass of Caucasian neonates was 2,515 g vs. that of 2,319 g of African American neonates (difference, P = 0.02). The corresponding figures for fat mass were 231 and 278 g, respectively (difference, P = 0.24). At 41 weeks, the Caucasians were 319 g heavier in lean body mass (P < 0.001) but were also 123 g heavier in fat mass (P = 0.001). The slopes for lean mass vs. gestational week were similar, but the slope of fat mass was 5.8 times greater (P = 0.009) for Caucasian (41.0 g/week) than for African American neonates (7.0 g/week).
Conclusions:
By 36 weeks of gestation, the African American fetus developed similar fat mass and less lean mass compared with the Caucasian fetus. Thereafter, changes in lean mass among the African American fetus with increasing gestational age at birth were similar to the Caucasian fetus, but fat accumulated more slowly. We hypothesize that different ethnic fetal growth strategies involving body composition may contribute to ethnic health disparities in later life.
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