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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 2, March/April 2017
AFRICA
89
camouflage the problem and propagate inherent imperfections
of the obesity-screening processes.
Cataloguing BMI, WC and sometimes waist:hip ratios may
not reflect their correlation to obesity-related sequelae. There
are medically healthy obese individuals and metabolically
obese normal-weight individuals, although the prevalence of
these conditions in this community is unknown. National
anthropometric data are scarce or unavailable.
The growing prevalence of overweight and obesity sweeping
southern Africa, with a national prevalence between 30 and
60% of populations over the age of 15 years, is largely due
to dietary shift away from high-fibre, low-calorie diets rich in
fruits and vegetables towards refined, energy-dense foods high
in fat, calories, sweeteners and salt, and this affects females
disproportionately.
18,19
A paradoxical situation, in which poverty
and high levels of overweight and obesity co-exist in urban
settings, may be explained by reduced levels of physical activity
in all groups. Coupled with rapid urbanisation, industrialisation
and increased sedentary lifestyles, these nutritional and
demographic transitions have ushered in the rapid emergence of
non-communicable diseases, including hypertension, diabetes,
stroke, heart disease and other cardiovascular diseases.
Despite direct correlations between BMI and WC, findings
from this situational analysis in Botswana suggest the need for
new cut-off points for WC (98 cm in men; 85 cm in women) that
correspond to a BMI of 30 kg/m
2
. Europid WC cut-off points
(
≥
80 cm in women;
≥
94 cm in men), as recommended by the
IDF
9
and currently used in sub-Saharan Africa to define central
obesity do not appear to correlate with BMI
≥
30 kg/m
2
in
Botswana. Elsewhere, there is a strong correlation between BMI
of 25–34.9 kg/m
2
, WC
≥
102 cm for men and
≥
88 cm for women,
and greater risk of hypertension, type 2 diabetes, dyslipidaemia
and coronary heart disease.
20
Western countries derived cut-off values of WC from
correlation with BMI, whereas Asians tried to define WC
cut-off values produced by receiver-operating characteristics
(ROC) curve analysis.
21,22
Measurements of skinfold thickness
are less accurate, particularly in obese individuals and are
therefore discouraged in routine screening exercises, except in
epidemiological studies. Precise measurements of body fat using
computed tomography (CT) or magnetic resonance imaging
(MRI) scans or biochemical barometers such as adipokines
are unlikely to be used outside research settings in Botswana.
However, measurement of fasting insulin and glucose levels may
help in the calculation of HOMA-IR in individuals with features
of insulin resistance syndromes.
In the Diabetes and Macrovascular Complications study of
258 adult diabetic patients in Botswana,
1
the MetS defined using
IDF criteria
9
was more prevalent in diabetic women compared to
diabetic men. Depending on which set of parameters in the IDF
criteria was used for the definition, the prevalence of the MetS
ranged from 41.7–83.7% in men, and 37.8–88.6% in women.
Obesity, defined by waist:hip ratio (
>
0.9 in men,
>
0.85 in
women) was present in 87.9% of diabetics, and by WC (
>
94 cm
men,
>
80 cm in women) in 79.0% of diabetics, but prevalence
of the MetS dropped to 38.3% using BMI (
>
30 kg/m
2
).
Large disparities in estimates of the MetS based on different
parameters complicated its true prevalence estimates in that
study. BMI was viewed as an insensitive indicator of the MetS,
especially in diabetic women.
Garrido
et al.
2
conducted a small cross-sectional, observational
study of 150 hospital workers at a peripheral facility in Botswana,
representing nearly half of the hospital workforce, women
comprising over 70% of the group. The investigators applied any
three or more of the ATP III criteria for definition of the MetS.
23
Low high-density lipoprotein (HDL) cholesterol affected 80%
of the group, dysglycaemia 73.3%, hypertension 44%, central
obesity 42% and hypertriglyceridaemia 14%. A third of the
participants met the ATP III criteria for the MetS and 28.7%
had a BMI
>
30 kg/m
2
. That over 40% of hospital employees
had central obesity, using higher cut-off points for WC raises
the possibility of a high prevalence of abdominal obesity in the
community.
Another cross-sectional study by Malangu
3
looked at 190
adult HIV-infected patients on highly active antiretroviral
therapy (HAART) at Princess Marina Hospital in Gaborone
in 2010. Their mean age was 42
±
9.04 years and nearly three-
quarters of the group were women (74.2%). Using IDF criteria,
the investigator showed an overall prevalence of the MetS
in 11.1% of participants. Risk factors for the MetS included
increased age, male gender and longer exposure to antiretroviral
drugs, particularly protease inhibitors. Only 10% of participants
had a BMI
>
30 kg/m
2
, 13 of 141 women and eight of 49 men had
abdominal obesity (WC
≥
80 cm in women and
≥
94 cm in men).
The study design lacked comparator control groups (e.g.
non-HIV-infected individuals or HIV-infected persons
pre-HAART), making it difficult to determine the independent
contribution of antiretroviral therapy to the MetS and this limits
generalisability of the findings. However, it appears that obesity
and the MetS were substantially lower in HIV-infected individuals,
despite the use of different diagnostic criteria for the MetS.
Studies fromother parts of sub-SaharanAfrica have generated
wide variations in WC cut-off points. For example, central
obesity defined by WC
>
102 cm in men and
>
88 cm in women
was more common than generalised obesity (BMI
>
30 kg/m
2
) in
Cotonou, Benin.
11
In South Africa, Motala
et al
.
12
found that WC
of
>
86 cm in men and
>
92 cm in women predicted the presence
of at least two elements of the MetS in a cross-sectional,
population-based study in a rural setting. That study was heavily
gender biased, with 80% of the 947 participants being female.
In 2014 Magalhães
et al
.,
13
in another cross-sectional study
of 615 university employees in Luanda, Angola, found overall
prevalence of overweight to be 47.8%, and obesity in 45.2%
of participants. Using JIS criteria, crude and age-standardised
prevalence of the MetS were 27.8 and 14.1%, respectively. The
crude and age-standardised prevalence of the MetS was 17.6
and 8.7% using ATP III criteria,
23
which apply higher WC cut-off
points (
≥
102 cm in men,
≥
88 cm in women).
Applying ROC curves of WC to detect the MetS, new cut-off
points of this study were 87.5 cm in men (sensitivity 75.9%,
specificity 81.2%) and 80.5 cm in women (sensitivity 88.4%,
specificity 60.5%). The three most common criteria for the
MetS were increased WC, hypertension and low serum HDL
cholesterol levels. Women showed a higher prevalence in all age
groups from the age of 30 years.
The INTERHEART study, a case-controlled study of 27 000
participants from 52 countries, showed a graded and highly
significant association between waist:hip ratios (WHR) and
acute myocardial infarction worldwide.
15
The association of
WHR with acute myocardial infarction in the INTERHEART