Summary
A preprint study of 1,268 South African adolescent girls found that DXA-measured body composition, particularly central fat distribution, is associated with elevated blood pressure. The findings highlight the importance of body composition balance and modifiable factors like sedentary behaviour.
Contents
Study design and participants
The study, posted as a preprint on medRxiv on 18 September 2026, is part of the Ntshembo trial and enrolled 1,268 girls aged 13–19 years from rural Agincourt and urban Soweto, South Africa. Participants were selected to include underweight and overweight individuals, creating a sample spanning nutritional extremes. Blood pressure was measured in triplicate at a single visit and classified into clinic BP category ranges. Body composition was assessed using dual-energy X-ray absorptiometry (DXA), which provided measures of fat mass (FM), fat-free soft tissue mass (FFSTM), and related indices. The study was approved by the Human Research Ethics Committee (Medical) at the University of the Witwatersrand (M211061) and is registered with the Pan African Clinical Trials Registry (PACTR202201638897606).
Key findings
Mean systolic blood pressure (SBP) was 110.0 ± 11.2 mm Hg and mean diastolic blood pressure (DBP) was 68.7 ± 8.2 mm Hg. Overall, 21.1% of participants had elevated or hypertensive-range blood pressure. Overweight adolescents had higher SBP and were more likely to fall into higher blood pressure categories compared with their underweight peers.
DXA-derived adiposity measures were positively associated with SBP and with higher blood pressure categories. Fat-free soft tissue mass (FFSTM) also showed a strong positive association with SBP. The ratio of fat mass to fat-free soft tissue mass (FM/FFSTM) was particularly strongly linked to abnormal blood pressure: compared with those with lower ratios, participants with higher FM/FFSTM had a relative risk ratio of 4.25 (95% CI 1.77–10.20) for elevated blood pressure and 19.04 (95% CI 6.43–56.40) for hypertensive-range blood pressure.
Two additional factors were independently associated with hypertensive-range blood pressure. Caregiver hypertensive-range blood pressure was associated with a relative risk ratio of 1.72–1.82 for adolescent hypertensive-range blood pressure. Sedentary behaviour was also independently associated with elevated blood pressure. The associations were more consistent for SBP than for DBP.
The researchers also performed regional percentage analyses, which suggested that a greater proportion of total fat distributed centrally rather than peripherally was consistent with higher blood pressure.
What the findings mean
The study adds detail to the understanding of how body composition relates to blood pressure during adolescence, a period when cardiovascular risk begins to accumulate. The findings indicate that both excess fat mass and greater fat-free mass are associated with higher systolic blood pressure, and that the distribution of fat—specifically a more central pattern—may be particularly important. The strong association with the FM/FFSTM ratio suggests that the balance of body composition, rather than overall weight alone, may be a useful indicator.
The independent association with caregiver blood pressure points to a possible intergenerational component, while the link with sedentary behaviour identifies a potentially modifiable target for intervention. However, because the study is cross-sectional, it cannot establish causality. The sample was selected to include underweight and overweight participants, so the results may not apply to all adolescents. In addition, the analysis is based on a preprint that has not yet undergone peer review.
The findings come from a single visit, so they do not capture how blood pressure or body composition change over time. Future longitudinal work would be needed to determine whether the observed associations predict later cardiovascular disease.