Research in context
Evidence before this study
We searched PubMed (with the medical subject heading search tool) on April 15, 2020, using the terms “body mass index” OR “anthropometry” AND “diabetes mellitus” AND “low- and middle-income countries” NOT “comment” NOT “case reports”. We searched for manuscripts published in any language from database inception to April 15, 2020. We found two pooled studies on the association between body-mass index (BMI) and diabetes. One study pooled nationally representative surveys from six low-income and middle-income countries (LMICs) and evaluated the association between BMI categories and non-communicable disease multimorbidity (including nine chronic conditions, one of which was diabetes). The second study pooled data on 900 000 individuals recruited from 18 cohorts across seven Asian countries and did not include nationally representative data. Several large studies on the prevalence and projected trends of overweight, obesity, and diabetes across LMICs have been published, but none of these studies have evaluated the association between BMI and diabetes risk in these settings and how this association varies by geographical region and sex.
Added value of this study
To our knowledge, this study uses the largest harmonised dataset collected to date of nationally representative, individual-level data on BMI and a biological measure of diabetes in 685 616 adults across 57 LMICs spanning six world regions. We did robust analyses, stratified by sex and geographical region, to assess the association between BMI (as a continuous and categorical exposure) and diabetes, defined biologically as a fasting plasma glucose concentration of 7·0 mmol/L (126·0 mg/dL) or higher; a random plasma glucose concentration of 11·1 mmol/L (200·0 mg/dL) or higher; or a glycated haemoglobin of 6·5% (48·0 mmol/mol) or higher, or by self-reported use of diabetes medication. We also present receiver operating curve analyses of optimal BMI cutoffs when assessing diabetes risk. The results show substantial variability in the association between BMI and diabetes risk by region and sex, and they add to our current understanding of the association between BMI and diabetes risk in countries poorly represented in previous literature.
Implications of all the available evidence
Given the rapidly growing burden of overweight, obesity, and diabetes in LMICs, urgent population-level strategies are needed to reverse current and projected trends. Additionally, our findings highlight that interventions and the BMI thresholds at which clinicians and policy makers consider metabolic risk to be increased vary across LMICs. Finally, in specific regions, screening might also need to include younger adults than is currently recommended by most guidelines.