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RESEARCH ARTICLE
SA JOURNAL OF DIABETES & VASCULAR DISEASE
44
VOLUME 14 NUMBER 2 • DECEMBER 2017
Obesity in Botswana: time for new cut-off points for
abdominal girth?
Churchill Lukwiya Onen
Correspondence to: Churchill Lukwiya Onen
Centre for Chronic Diseases, Gaborone, Botswana
e-mail:
onenkede@info.bwPreviously published in
Cardiovasc J Afr
2017;
28
: 86–91
S Afr J Diabetes Vasc Dis
2017;
14
: 44–49
Abstract
Introduction:
Country-specific cut-off points for defining
central obesity in black Africans are long overdue.
Methods:
Anthropometric data from 215 (51.4%) male and
203 (48.6%) female patients seen in Gaborone between
2005 and 2015 were analysed to establish appropriate
cut-off points for waist circumference (WC) corresponding
to a body mass index (BMI) of 30 kg/m
2
. Relative risks for
cardiometabolic disorders were calculated for different BMI
and WC categories using MedCalc
®
. The subjects’ mean age
was 50.0 ± 10.8 years and 80.6% were Batswana.
Results:
Only 7.2% of patients had a BMI < 25 kg/m
2
, 27.3%
were overweight and 65.5% were obese; mean BMI was
34.9 ± 6.5 kg/m
2
in the women versus 31.0 ± 4.9 kg/m
2
in
the men (
p
< 0.0001). New cut-off points of 98 cm in men
and 85 cm in women emerged. Different weight and WC
categories appeared not to confer increased relative risk of
hypertension, dysglycaemia or dyslipidaemia.
Conclusion:
The proposed WC cut-off values, if validated,
should set the pace for larger studies across sub-Saharan
Africa.
Keywords:
Botswana, obesity, waist circumference, cut-off points,
modelling
Several small observational studies in Botswana have produced
inconsistencies in the prevalence of the metabolic syndrome
(MetS), partly because of variations in methodological approaches
to measurements of waist circumference and differences in study
populations.
1-3
Although Botswana was one of the poorest countries
at independence, its diamond-dependent economy has propelled it
to upper-middle income, with one of the fastest-growing economies
in the world, gross domestic product of $18 825 per capita in 2015,
the fourth largest gross national income, and the highest human
development index in sub-Saharan Africa.
4,5
It is currently estimated that 57% of the population is urbanised.
Overweight and obesity are therefore assuming epidemic
proportions in the country. Life expectancy at birth is 63 and 65
years in men and women, respectively.
6,7
This represents a 14-year
increase for both genders between 2000 and 2012. The probability
of dying between the ages of 15 and 60 years in men and women
is 321 and 254 per thousand of the population, respectively.
In 2012, HIV/AIDS accounted for a third of the causes of mortality
(5 700 deaths), whereas stroke, ischaemic heart disease, diabetes
mellitus and hypertensive heart disease together accounted for
about 15% of deaths (2 900 deaths). Cardiovascular diseases and
diabetes together constituted the third most common cause of
disability-adjusted life years (DALYs).
Since its description by Jean Vague
8
nearly seven decades ago,
abdominal obesity consistently features among criteria for the
definition of the MetS, although the clustering of cardiovascular
risk factors has greatly expanded. Obesity is also the bedrock in
the International Diabetes Federation (IDF) definition of the MetS.
9
The Joint Interim Statement (JIS) on the MetS recommended the
use of population- and country-specific cut-off points to define
an enlarged waist circumference.
10
Accordingly, using non-
validated cut-off points for waist circumference in the definition
of obesity may falsify estimates of the MetS in the African setting.
Inconsistent estimates of the MetS in sub-Saharan Africa have
largely been due to lack of African-specific cut-off points for waist
circumference.
11-13
This study aimed firstly to determine the validity of current
operational waist circumference cut-off points in Botswana;
secondly, to determine the correlation between body mass index
(BMI) and waist circumference (WC) in black African men and
women, and in particular, the relationship between BMI of 30 kg/
m
2
and WC of 80 cm in women and 94 cm in men; and thirdly
whether excessive body weight relates to cardiometabolic and
other chronic medical disorders in the study population.
Methods
Data from a heterogeneous group of adult patients seen over a
10-year period (2005–2015) at a specialised medical clinic I run
in Gaborone city were extracted from conveniently sampled case
notes, taking every sixth file from over 3 000 files accumulated in
the filing room during a decade of private practice. Completeness
of records was examined for the presence of weight (kg), height
(cm), waist circumference (cm) and co-morbidities for each patient
during the index visit.
From the inception of the clinic at Gaborone Private Hospital,
anthropometric measurements have been routinely performed
whenever possible, using standard methods. Weight (kg) and
height (cm) were measured in a similar manner to the method
described by Dowse and Zimmet,
14
using a well-calibrated scale.
BMI was derived by dividing weight (kg) by the square of height
(m
2
). Able-bodied participants were instructed to stand upright
with the back against the stand, heels together and eyes directed
forward so that the top of the tragus of the ear was horizontal with
the inferior orbital margin, and the measuring plate was lowered
on to the scalp to give the correct height.
Waist circumference was measured with the individual standing
upright with the side turned to the observer, who was often seated.
A measuring tape attached to a spring, similar to that used in the
INTERHEART study,
15
was placed snugly in a horizontal plane around