Cardiovascular Journal of Africa: Vol 27 No 6 (November/December 2016)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 6, November/December 2016 AFRICA 371
activity, walking for travel, absolute dietary intake or DQI-I
between BMI groups (data not shown). Those who smoked at
baseline had a significantly higher BMI than those who did not
smoke.
Baseline housing density and asset index were not associated
with change in body weight, body composition or body fat
distribution. By contrast, other SES variables at baseline and
the changes in these variables were associated with changes in
body weight or changes in body composition over the follow-up
period (Table 3). Baseline and changes in access to sanitation and
employment had siginficant effects on weight gain over the 5.5
years, while education and contraceptive use did not.
Nulliparty had significant associations with changes in body
weight as well as changes in body fat distribution. Parity was
associated with redistribution of fat mass, with larger decreases
in appendicular fat mass (percentage of total fat mass) (–3.1 ±
2.9 vs –1.5 ± 2.7%, p = 0.040) and gynoid fat mass (percentage of
total fat mass) (–1.1 ± 1.0 vs –0.5 ± 1.2%, p = 0.088), and larger
increases in trunk fat mass (percentage of total fat mass) (3.69
± 3.5 vs 1.9 ± 3.1%, p = 0.044) and trunk:leg ratio (0.19 ± 0.2 vs
0.08 ± 0.1%, p = 0.004) in the nulliparous women compared to
the women with children at baseline.
Furthermore, those women who were still nulliparous at
follow up (n = 9) increased their body weight significantly more
over the 5.5-year follow-up period than their childbearing
counterparts (p = 0.001). There was a trend for those who
had children over the 5.5-year period to increase their body
weight less than those who already had children, but it was not
significant after adjusting for baseline age and BMI. Those who
increased their education level (n = 11) had a greater increase
in relative trunk fat mass (percentage of fat mass) compared to
those who did not (n = 53) (p = 0.035).
Dietary intake and physical activity at baseline, and baseline
and follow-up smoking and alcohol intake were not associated
with changes in body composition (data not shown).
Multiple regression analysis was used to explore the
independent determinants of the changes in body weight and
body fat distribution over the 5.5-year follow-up period (Table
4), based on the significant univariate analyses described above.
Based on the regression model, increasing body weight over time
was associated with a lower baseline BMI, being nulliparous at
baseline, not having children during the follow-up period, lack
of household sanitation at baseline and improved sanitation
at follow up. This model explained 51% of the variance in the
change in body weight (p < 0.001). The model that explained
the greatest variance in the change in relative trunk fat mass
(percentage of fat mass), change in trunk:leg ratio and change
in relative gynoid fat mass (percentage of fat mass) (model B)
included only baseline BMI and being nulliparous at baseline.
Discussion
The main findings of this study were that lower BMI and
nulliparity, together with sanitation as a proxy for SES, were
significant determinants of weight gain and change in body fat
distribution over a 5.5-year period in a sample of free-living peri-
urban black SA women. In addition, younger women increased
their body weight more than their older counterparts, but this
association was not independent of baseline BMI.
The finding that there was an inverse relationship between
baseline BMI and weight gain is similar to other studies in
HICs. Few researchers have highlighted the effect of baseline
BMI as a predictor of future weight gain. Brown et al.5 showed
that a baseline BMI of 25–30 kg/m2, in conjunction with a high
energy intake, was a significant determinant of weight gain over
five years in middle-aged Australian women. Another study in
the USA reported greater weight gain in those who were both
younger and who had a lower baseline BMI.4 In addition, this
study showed that a lower baseline BMI was associated with a
greater redistribution of fat from the periphery to the central
depots over time. The women with a lower BMI may have
a higher capacity for increasing body weight and increased
centralisation of fat mass over time. This highlights a group
that is at increased risk and should be targeted for future
interventions aimed at preventing an increase in body weight
and centralisation of fat mass over time, due to the associated
negative cardiometabolic outcomes. 18
Table 4. Multivariate models for changes in
body composition over the 5.5-year period
Change in body weight (kg)
Variable β SEE p-value
Baseline BMI –0.24 0.13 0.016
Presence of
running water
and a flush toilet
–0.28 2.66 0.023
Improvement in
sanitation (toilet
and water)
0.30 2.41 0.005
Child/children at
baseline
–0.42 2.07 0.000
Children over
follow-up period
–0.25 2.12 0.025
R2 = 0.51, p < 0.001 VIF: 1.25.
Change in body fat distribution
Variable Δ Trunk FM (% FM)
(R2 = 0.43) (p < 0.001)
Δ Trunk:leg
(R 2= 0.35) (p < 0.001)
Δ Gynoid FM (% FM)
(R2 = 0.20 (p = 0.001)
VIF 1.02 1.02 1.02
β SEE p-value β SEE p-value β SEE p-value
Baseline BMI –0.61 0.04 < 0.001 –0.47 0.00 < 0.001 0.40 0.02 0.001
Child/children
at baseline
–0.34 0.69 0.001 –0.42 0.03 < 0.001 0.22 0.27 0.022
Table 3. Change in body weight and trunk fat mass in response to
differences in SES/behaviour/lifestyle variables
SES/behaviour/lifestyle variable
Change in body weight (kg)
n Yes n No p-value
Access to inside running water at
baseline?
16 1.7 ± 11.2 45 8.8 ± 8.8 0.012
Access to inside flush toilet at
baseline?
16 2.3 ± 12.1 45 8.5 ± 8.8 0.032
Employed at baseline? 20 10.2 ± 10.9 41 5.1 ± 8.7 0.050
Grade 12 at baseline? 21 7.2 ± 8.8 40 6.5 ± 10.3 0.803
Hormonal contraceptive use at
baseline?
30 8.0 ± 8.9 31 5.5 ± 10.6 0.982
Nulliparous at baseline? 25 10.7 ± 9.5 36 3.8 ± 8.9 0.005
Nulliparous at follow up? 9 16.6 ± 7.2 52 5.4 ± 9.3 0.001
Improvement in sanitation over
time?
14 15.1 ± 7.5 44 4.8 ± 9.4 < 0.001
Loss of employment over time? 8 11.7 ± 6.4 53 5.8 ± 11.6 0.043
Change in trunk fat mass (% TFM)
n Yes n No p-value
Improvement in level of education
over time?
11 2.2 ± 3.3 53 4.6 ± 3.1 0.035
Nulliparous at baseline 25 3.7 ± 3.5 36 1.9 ± 3.1 0.044