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Physical Activity and Adiposity in a Racially Diverse Cohort of US Infants
Sara E Benjamin-Neelon1, Jiawei Bai2, Truls Østbye3
1Department of Health, Behavior and Society, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
Insights
Infant physical activity increases during the first year and is linked to less central body fat. Objective measurement methods are recommended for future infant obesity prevention research.
Area of Science:
- Pediatrics
- Public Health
- Biomedical Engineering
Background:
- Early life physical activity is crucial for preventing childhood obesity.
- Objective quantification of physical activity in infants presents significant challenges.
- Understanding infant physical activity patterns is essential for early intervention strategies.
Purpose of the Study:
- To objectively quantify physical activity levels in infants throughout the first year of life.
- To examine the trends of physical activity in infants over time.
- To investigate the association between objectively measured physical activity and adiposity indicators in infants.
Main Methods:
- A cohort of 506 infants was monitored using accelerometers for 4 days at 3, 6, 9, and 12 months of age.
- Log-transformed physical activity counts were computed, standardized, and analyzed using linear mixed models.
- Associations between physical activity and BMI z-score, overall adiposity (SS+TR), and central adiposity (SS:TR) were assessed.
Main Results:
- Physical activity counts significantly increased with each assessment visit during infancy (P < 0.0001).
- A 1-SD increase in physical activity was associated with a significant reduction in central adiposity (SS:TR) (P = 0.03).
- No significant associations were found between physical activity and BMI z-score or overall adiposity (SS+TR).
Conclusions:
- Infant physical activity demonstrates a positive trend throughout the first year of life.
- Objectively measured physical activity in infancy is associated with reduced central adiposity.
- Despite measurement challenges, objective quantification of infant physical activity is vital for obesity prevention research.
Objective:
Early life physical activity may help prevent obesity, but objective quantification in infants is challenging.
Methods:
A total of 506 infants were examined from 2013 to 2016. Infants wore accelerometers for 4 days at ages 3, 6, 9, and 12 months. Daily log-transformed physical activity counts were computed, averaged, and standardized across assessments. A linear mixed model was used to examine trends in standardized physical activity counts as well as associations between physical activity and BMI z score, sum of subscapular and triceps skinfold thickness for overall adiposity (SS+TR), and their ratio for central adiposity (SS:TR).
Results:
Among infants, 66% were black and 50% were female. For each additional visit, standardized physical activity counts increased by 0.23 (CI: 0.18 to 0.27; P < 0.0001). This translates to 126.3 unadjusted physical activity counts or a 4% increase for each visit beyond 3 months. In addition, a 1-SD increase in standardized physical activity counts (550 unadjusted physical activity counts) was associated with a 0.01-mm lower SS:TR (95% CI: -0.02 to -0.001; P = 0.03). However, standardized physical activity counts were not associated with BMI z score or SS+TR.
Conclusions:
Physical activity increased over infancy and was associated with central adiposity. Despite limitations, researchers should consider objective measurement in infants.
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