There is a story we tell ourselves about hunger and body weight in Africa, and it goes roughly like this: poverty causes undernutrition, and wealth brings better diets. It is a tidy narrative, and like many tidy narratives, the evidence is beginning to complicate it considerably.
A new CGIAR research brief, titled Diets and Nutrition in Arusha and Kilimanjaro, assessed the nutritional status of approximately 2,600 women of reproductive age across both regions, categorising them as underweight, normal weight, overweight, or obese using standard Body Mass Index thresholds. What it found challenges policymakers, development practitioners, and nutrition advocates to rethink some foundational assumptions.
The Numbers
Across both regions, a high proportion of women were living with overweight or obesity. In Arusha, 24% of women were classified as overweight and 16% as obese. In Kilimanjaro, the figures were higher: 31% overweight and 30% obese. Combined, that means more than half of the women surveyed in Kilimanjaro were living above a healthy weight.
A higher proportion of women in Arusha, 53%, compared to Kilimanjaro, 35%, were considered normal weight. The prevalence of undernutrition, meaning underweight status, was generally low across both regions, but somewhat higher in Arusha at 8% compared to 3% in Kilimanjaro.
Underweight was defined as BMI below 18.5 kg per square metre. Normal weight was defined as BMI between 18.5 and 24.9. Overweight covered 25.0 to 29.9, and obesity was defined as BMI at or above 30.0.
The Paradox: Wealth and Weight
Here is where the data becomes uncomfortable. The brief notes that overweight and obesity were more prevalent among older and less educated women, as well as among women in the wealthiest households and those living in more urbanised villages.
The wealth connection is significant. In many development contexts, policymakers target nutritional interventions at the poorest communities, and rightly so, because undernutrition and micronutrient deficiency remain serious concerns in those settings. But the finding from Arusha and Kilimanjaro suggests that rising income, rather than automatically protecting women from nutrition-related disease, may be exposing them to a different set of risks.
The likely mechanism is dietary transition. As households gain purchasing power, they tend to shift away from traditional diets heavy in vegetables, legumes, and whole grains towards diets that include more processed foods, cooking oils, refined carbohydrates, and animal products. The market reinforces this shift: processed and packaged foods are more widely available at community-level shops than fresh produce.
Urbanisation as a Risk Factor
The urbanisation link is equally telling. Women living in more urbanised villages showed higher rates of overweight and obesity. This aligns with what researchers increasingly call the urban nutrition penalty: city and peri-urban environments, while offering income opportunities and better market access, also expose residents to food environments dominated by fast foods, snacks, and convenience items rather than nutrient-rich whole foods.
Tanzania’s agricultural regions are urbanising rapidly, and this finding suggests the nutritional consequences are already visible in the data, even in regions that are not yet fully urban.
The Research Agenda
The CGIAR team is explicit about the next steps. Having established this baseline, they aim to understand if and how better diets are associated with lower risk of overweight and obesity, and they will test whether interventions to improve fruit and vegetable intake can help reduce the prevalence of these conditions among women of reproductive age.
This is the central wager of the entire research programme: that improving what women eat, specifically by increasing their intake of fruits and vegetables, can interrupt the trajectory towards NCDs that both poverty and rising prosperity seem, in different ways, to be driving.
The evidence gathered so far shows how far Tanzania is from that goal. Nearly half of all women of reproductive age in Tanzania live with overweight or obesity, according to the Tanzania Demographic and Health Survey and Malaria Indicator Survey of 2022. The CGIAR brief confirms that Kilimanjaro and Arusha are no exception, and in some categories, they are doing worse.
The paradox is not the end of the story. But it has to be the starting point.