Our findings show that the combined prevalence of overweight and obesity among women intending to become pregnant within the next four years is very high in Tanzania. Overall, we found that being older, having informal employment and middle to high socioeconomic status were associated with overweight and obesity among women in Dar es Salaam, Tanzania. The study found an association between vigorous physical activity and decreased overall prevalence of overweight and obesity. Sugary dietary intake was associated with an increased prevalence of overweight and obesity. Consumption of protein from fish and poultry was associated with a lower risk of overweight and obesity after adjusting for energy intake and physical activity.
More than half of the women in our study are either overweight or obese, which is higher than the 2015 national prevalence in urban settings (50.7% vs 42.0%) in Tanzania . Women in this study had a 6-fold higher prevalence of overweight and obesity in women than underweight (8.6%). This is of great concern considering nutritional counselling in many antenatal health care services; the emphasis is on maternal weight gain and less on the overweight and obese control (a personal conversation with the health facility providers in the study area). High prevalence of maternal obesity is also reported in a systematic review and meta-analysis across Africa, ranging from 6.5–50.7% . This has been mainly attributed to economic and nutrition transition, which have exposed women to sedentary life and unhealthy diets [27, 28]. Such a high prevalence of overweight and obesity in women who intend to conceive within the next few years is alarming considering the reported maternal and newborn adverse outcomes associated with pre-pregnancy high BMI such as gestational hypertension, diabetes mellitus, macrosomia and infant mortality [9, 11].
Being older, having informal employment, and middle to high socioeconomic status were associated with an increased prevalence of overweight and obesity in this study. These findings are consistent with other studies that reported a higher prevalence of overweight and obesity in older women [15, 29, 30]. Obesity among older women may be attributed to increased parity, hormonal changes and a less active lifestyle as women grow older [31, 32]. In addition, weight retained during pregnancy is often difficult for women to lose, even for obese women, contributing to increased BMI over time .
Women who were self-employed or under the informal employment sector, such as street vendors, shopkeepers, and tailors had a higher prevalence of overweight and obesity compared to women who were unemployed or formally employed. The role of employment status as a determinant of BMI is not clear but, studies have shown that white-collar workers are at the greatest risk of low occupational physical activity levels and sedentary behaviour [34, 35]. In this study, women under formal employment in most cases were in the white-collar job category; however, this was not associated with increased risk of overweight and obesity. There is, therefore, a need to understand the nature and actual contribution of specific employment status to women’s BMI.
We found that women with higher economic status had a higher prevalence of overweight and obesity. Similar findings have also been reported by other studies from SSA, where socioeconomic status was an important determinant of overweight and obesity [15, 30, 36]. This may be due to socio-cultural factors and perceptions in many LMICs that favours women having larger body size [37, 38]. Being obese or overweight in many African countries have been perceived as a sign of being wealthy, having enough to eat, and less associated with diseases such as HIV infection [39, 40]. More importantly, wealthier households can afford more calories in their diets and may be more able to purchase processed and unhealthy foods, eat fast food from restaurants etc., while also being less likely to be physically active . The findings are contrary to many studies in high-income countries where adults with higher socioeconomic status have a low prevalence of obesity [42, 43].
Besides controlling dietary intake, having sufficient exercise and physical activity is considered an effective approach for controlling weight gain . This is in line with our findings that women who met moderate to severe total physical activity criteria (MVPA) had a lower prevalence of overweight and obesity by 21%. Similar findings were found in a study among Ghanaians where women who did not meet the recommended physical activity level had increased risk of obesity by 23% . Physical activity, including aerobic exercises, reduces fat mass and body weight .
We found that high consumption of sugar was associated with a higher prevalence of overweight and obesity, which is consistent with findings from a systematic review in SSA. The review found that a steady increase in the availability and consumption of energy-rich foods from the 1980s had contributed substantially to the increase of obesity in the region . High sugar and beverages consumption above 10% of the total daily energy as recommended by the WHO has increased in recent years, especially in urban settings including Tanzania . Thus, this calls for immediate attention considering that high sugar intake is associated with non-communicable diseases . Animal protein and fat intake were not associated with increased risk of overweight and obesity. This is contrary to the USA and European study, which associated animal protein intake with increased risk of both global and abdominal obesity. Fish and poultry protein intake was significant associated with low risk of overweight and obesity. Compared to the animal (red) meat, both fish and chicken have less saturated fat and cholesterol, which justifies having less risk of overweight and obesity .
Our study is one of the few studies in SSA that has measured physical activity and dietary intake given the current situation of unprecedented urbanization and dietary transmission in many African countries. Therefore, we believe the findings are vital to underpin the importance of addressing overweight and obesity determinants in the region, including physical activity and healthy diets. However, we cannot ignore the possibility of a recall bias as some respondents may fail to remember foods consumed in the past 30 days. Additionally, we utilize a cross-sectional study design which may be affected by confounding. In this study, we also adjusted for energy intake and known potential confounders to address confounding issues. Additionally, in the models for dietary intake, we also controlled for physical activity.