Associations between abdominal adiposity, body size and objectively measured physical activity in infants from Soweto, South Africa.
Maternal and Child Health Journal 2022
PubMed ID : 35612772
Considering the importance of the early life period, in conjunction with the increasing prevalence of adiposity and insufficient physical activity already evident in early childhood, this study aimed to determine associations between abdominal adiposity, body size, and objectively measured physical activity in infancy.
Infants (n = 138, aged 3-24 months) from Soweto, South Africa were recruited to this cross-sectional study. Visceral (VAT) and subcutaneous abdominal fat (SAT) were measured using ultrasound. Physical activity was assessed using accelerometry and analysed at the hourly level. Multilevel linear regression analyses were run with body composition exposures adjusted for age, sex, and length; models with VAT and SAT were also adjusted for total abdominal fat.
Mean (SD) age was 11.8 (7.6) months; 86% were normal weight, 7% were underweight and 7% overweight. In linear models, no body composition variable was significantly associated with physical activity. Physical activity was higher with each increasing length tertile (ANOVA p < 0.01); with a mean(95%CI) 29(60-60)mg in the lowest tertile, 39(71-71)mg in the middle tertile, and 50(81-82)mg in the highest tertile. Infants with normal weight had higher mean(95%CI) physical activity (40(70-80)mg) than underweight (34(73-85)mg, p = 0.01) or overweight infants (31(63-78)mg, ANOVA p < 0.01). When also adjusting for total abdominal fat, infants in the lowest SAT tertile had higher physical activity than those in the middle or highest SAT tertiles (p < 0.01).
These findings lend support for higher physical activity as a marker of healthy growth in the first two years of life.
The first two years of life are a critical period for children to develop trajectories for better health later in life. This includes establishing healthy lifestyle patterns, such as being physically active and eating well; and growing at the right pace to avoid metabolic complications such as obesity. Globally however, young children are not sufficiently active, and present with obesity from very young ages. Considering this, our study aimed to assess whether physical activity in the first two years of life was associated with abdominal fat accumulation, weight and height.
We assessed 138 children aged between 3-24 months who lived in Soweto, an impoverished semi-urban area in South Africa. We measured how much fat they had around their abdominal region using an ultrasound machine, and measured how physically active they were using small devices attached at the wrist called accelerometers, which function similarly to a fitness tracking watch. We then categorised children’s weight, height, and fat accumulation as “low”, “normal”, or “high”; and examined if their physical activity levels were related to which category they fell into.
We found that 7% of the children were underweight, while another 7% presented with overweight. Children who were taller, normal weight, and had normal abdominal fat accumulation were more physically active; while children who were shorter or overweight were less physically active. However, when removing the categories and looking at length, weight and fat accumulation as a continuum, physical activity was no longer associated – indicated that these relationships are not straightforward, but rather that there are differing relationships with physical activity for children with low vs medium vs high weight, length, and fat values. These findings show that we could use physical activity in children as an indicator for healthy growth in the first two years of life.