Obesity epidemic has emerged among Nigerians

Overweight and obesity, defined by the WHO as body-mass index ≥ 25 kg/m² and ≥30 kg/m², respectively, are associated with several diseases including cardiovascular disease, diabetes and several types of cancer cancer and cardiovascular disease [1]. In 2008, 1.4 billion adults aged 20 years and above were overweight or obese, of whom approximately 200 million men and 300 million women were estimated to be obese [2]. Although it had been projected that by 2030, there will be 2.16 billion overweight and 1.12 billion obese individuals globally [3], results from trend analysis suggest that 2 or more billion people worldwide are currently overweight or obese [4]. High blood pressure and high fasting plasma glucose were leading risk factors for disease worldwide in 2010 [1] and are in part caused by obesity. The global disease burden attributable to high body-mass index increased from 52 million in 1990 to 94 million disability-adjusted life-years in 2010 [1].

Although more people in developing countries now die from obesity-associated diseases, including ischemic heart disease, diabetes mellitus and cancer [5], many people are still under the impression that overweight and obesity affects only the Western world and that lower resource countries continue to struggle with only underweight, malnutrition and infections. This may not be the case because the obesity epidemic is growing faster in developing countries than in the developed world [6]. Among people aged 15 years and above, the WHO estimated that the prevalence of overweight and obesity in 2010 was as high as 63.8% and 21.3% respectively, for men, and 73.8% and 43.2% respectively, for women, in some Sub-Saharan Africa countries. Eritrea, Ethiopia, Democratic Republic of the Congo and Central African Republic had the lowest prevalence, while Seychelles, Lesotho, South Africa and Mauritius had the highest prevalence of overweight and obesity in Sub-Saharan Africa [7]. In general, the countries with lower prevalence of overweight and obesity tend to be those with low gross domestic product per capita and vice versa, suggesting that socio-economic status may be a determinant of overweight and obesity in some African countries.

According to the 2010 WHO survey data on Nigeria, the prevalence of overweight was 26% and 37% in men and women respectively, while the prevalence of obesity was 3% and 8.1% in men and women respectively [7]. Data from the WHO Global InfoBase, based on individuals aged 30 years and above, shows that the prevalence of overweight and obesity together increased by 23% in men and 18% in women, while the prevalence of obesity alone increased by 47% in men and 39% in women, between 2002 and 2010, in Nigeria [7].

Previous studies have shown that several factors including age, gender, marital and socio-economic statuses, occupation, urban residence, dietary intake and physical activity are associated with overweight and obesity [8‐12]. Even though the prevalence of overweight and obesity in Nigeria continues to increase, there are few studies of its correlates. We therefore conducted this study to examine the prevalence of overweight and obesity and its potential correlates in an urban Nigerian population.

The mean age (SD) of the participants was 41.6 (9.3) years; 40% (416/1041) were women and 60% (625/1041) were men. The mean (SD) body-mass index of all the participants was 27.2 (4.8) kg/m²; 36% (377/1041) of the study participants were of normal weight 38% (399/1041) were overweight and 26% (265/1041) were obese. The mean (SD) body-mass index was 22.5 (1.6) kg/m² for the participants within the normal weight range, 27.2 (1.4) kg/m² among the overweight and 33.8 (3.2) kg/m² for those who were obese. Table 1 shows the demographic characteristics of the study population overall and by body-mass index categories. Some 32% (134/416) of the women and 42% (265/625) of the men were overweight, while 42% (174/416) of the women and 15% (94/625) of the men were obese. Table 2 shows the prevalence of overweight and obesity by gender.

Individuals who were older than 30 years were more likely to be overweight or obese than younger persons. Compared to individuals aged < 30 years, the prevalence ratio (PR) for being overweight was 1.45 (95% CI = 1.07, 1.97) for individuals aged 40 – 49 years and 1.35 (95% CI = 0.98, 1.85, p-value for trend test = 0.002) for individuals aged 50 years and above; while the PR for obesity was 8.07 (95% CI = 3.01, 21.66) for individuals aged 40 – 49 years and 7.74 (95% CI = 2.88, 20.81 p-value for trend test = <0.0001) in individuals who are 50 years of age and above. The prevalence of overweight and obesity was related to age in a non-linear manner (p < 0.001). Both conditions increased linearly with age up to around age 45, at which point the prevalence of these conditions remained constant or even declined (Figure 1). Comparing women to men, the PR and 95% CI for overweight and obesity were 1.24 (95% CI = 1.08, 1.43 p = 0.004) and 2.54 (95% CI = 2.08, 3.10 p = <0.0001, respectively. Being married was also associated with increased prevalence of overweight and obesity. Table 3 shows the results of univariate and multivariate analyses of the risk factors for the prevalence of overweight while Table 4 shows the same information for obesity.

Higher occupational level and a higher socio-economic status were significantly associated with an increased prevalence of obesity but not overweight. The PR for obesity among those in the middle and high socio-economic categories, were 1.39 (95% CI 1.13, 1.72) and 1.24 (95% CI 0.97, 1.59) respectively, p for trend = 0.003, compared with the lower socio-economic status category

Only 36% of the participants in this study had normal body-mass index, the remaining 64% were either overweight or obese. Factors that were significantly associated with higher prevalence of overweight and obesity were being in older age groups, and female gender. In addition, having a more professional job and belonging to middle or high socio-economic status were significantly associated with increased obesity prevalence.

Some 77% of our study participants had at least a college degree and 50% had professional jobs. Data from the 2008 Nigeria Demographic and Health Survey [24] shows that Abuja, federal capital territory, has the highest proportion of men and women who have completed a secondary school education, among all 36 states and the federal capital territory, in Nigeria. Our findings are consistent with studies on obesity in Sub Saharan Africa, that the prevalence of obesity was more marked among urban, highly educated women [8], who are more likely to have sedentary lifestyles and access to processed foods, compared to women in rural areas.

The findings from our spline analysis showed that, the prevalence ratio of obesity increases rapidly after age 30 years and peaks at age 40 – 49 years. Our findings, on the prevalence of overweight and obesity among adults aged 30 years or older in Nigeria, were higher than in the WHO 2010 survey [25]. However, unlike our study which was based on an urban population, the WHO survey included rural and urban populations. Our estimates were also substantially higher than estimates from other recent studies in Nigeria. Table 5 shows how the prevalence estimates obtained from these studies, compare to our prevalence estimates and the setting for each study population. In contrast to these studies, our study sample was urban, more educated and more likely to be engaged in professional vocations compared to average Nigerians [24]. As the Nigerian economy continues to improve, food availability and individuals’ dietary calorie intake may have increased, thus contributing to more people becoming overweight and obese. People living in rural Nigeria still consume more traditional Nigerian diets which have more whole grains, have higher fiber and fewer calories. They may also have less sedentary lifestyles compared to those in the urban areas. However, there is scarce data, on the nutritional and physical activity patterns, among Nigerians.

Our results are consistent with other African studies, that overweight and obesity is more prevalent among women, persons older than 30 years and married individuals [9, 11, 12, 28, 32]. The gender disparity among overweight and obesity is not well understood. However, weight gain during and after pregnancy, the perception of weight gain as evidence of high socio-economic status [33], fattening practices among women [34, 35] and increased prevalence of more sedentary occupations among Sub-Saharan African women, may contribute to this. Although women in Africa may do more household chores, men’s professions and work related to engaging in these occupations, participation in sports and other physical activities, may contribute to the different prevalence between men and women [15]. In addition, Nigerian women in urban areas who are highly educated and have higher socio-economic status, may not engage in household chores as they are more likely to have maids who do the work.

Higher socio-economic status and occupational level were significantly associated with the risk of obesity. This finding was consistent with the pattern of results in low- and middle-income countries [10]. We noted that those that were at least moderately physically active were more likely to be overweight or obese, even though this was not statistically significant. Some of these people may include those trying to lose weight. Also, obesity and overweight was more prevalent among those reporting consumption of fewer carbohydrate calories. This may be due to underreporting of dietary intake by those who were overweight and obese [36, 37]. People with higher dietary calorie intake are also likely to be more physically active. Unlike studies done in developed countries where hours spent watching TV is associated with obesity [38], we did not find this to be the case in this study population.

The prevalence of overweight and obesity in Abuja is high, compared to other cities in Nigeria [9, 26‐30] but it is similar to the prevalence in developed countries like the United Kingdom, where a greater proportion of men than women (42% compared with 32%) were classified as overweight and 26% of the adults were classified as obese in 2010 [39]. This dramatically increasing prevalence is of particular concern, in view of increased risk of non-communicable diseases such as hypertension, diabetes and cancer. Our findings argue for public health interventions that seek to promote healthy diets and increase physical activity, among the rapidly urbanizing populations, particularly of the developing world.

Our study is limited by its cross-sectional design and its setting in an adult urban population, thus the results cannot be generalized to rural populations or children. As there were many different ethnic groups, we did not have sufficient power to address the role of these unique ethnicities on overweight or obesity. Also, dietary carbohydrate intake was assessed over the past year, which may not be the best representation of the participants’ long-term intake. However, we made objective measurements of anthropometry, using standardized guidelines and techniques, and we found correlates of overweight and obesity in this Nigerian population, that were similar to other highly urban populations in West Africa [9, 11, 12].

In conclusion, our findings emphasize the importance of implementing population-wide approaches to reduce diseases associated with increasing urbanization such as obesity in rapidly developing countries like China and Nigeria. Future studies on diet, physical activity and their determinants in urban populations are urgently needed. Specific urban public health policies to promote awareness especially among young adults, education, nutritional interventions, improved urban neighborhood planning and increased physical activity, should be integrated in national health policies to help control this epidemic in Africa.