Association between BMI and diabetes risk among low-middle income countries varies considerably by geographical region

1. Standard BMI thresholds associated with greater risk of diabetes varied across 57 low- and middle-income countries depending on geographical region.

2. Younger individuals are also at greater risk of diabetes depending on geographical region, notably for men aged 25-34 in sub-Saharan Africa. 

Evidence Rating Level: 2 (Good)

Study Rundown: Body mass index (BMI) is a commonly used clinical measurement to assess risk of developing type 2 diabetes. However, there is a scarcity of recent studies comparing the association between BMI and type 2 diabetes in low- and middle-income countries (LMIC). This large-scale cross-sectional study of 685 616 adults across 57 LMICs analyzed data from the WHO Stepwise Approach to Surveillance (STEPS) survey and other population-level surveys. Overall prevalence of obesity or overweight BMI was 48.2% among the LMICs surveyed. The pooled results from all countries showed an increased risk of diabetes once BMI exceeded 23 kg/m² (upper-normal). For sex and age analysis, diabetes risk was generally higher in men than women and increased sharply at the 35-44 age group in all countries except for men in sub-Saharan Africa, where it began at 25-34 years. When stratified by geographical region, diabetes and BMI association varied greatly. With these results, the study provided a ROC-derived analysis for recommended BMI screening cut-offs. In other words, the clinically important BMI in which a demographic becomes at-risk of type 2 diabetes. This value was lowest (23.8) for men in east, south, and southeast Asia and highest (28.3) for women in the Middle East, north Africa, Latin America, and the Caribbean. Limitations of this study include the use of BMI as a single measure of risk for diabetes, as BMI is not an accurate measure of body fat percentage, but a rough estimation. However, BMI is a suitable proxy as body fat percentage would not be a routine clinical measurement performed. Nevertheless, this study provides large-scale analysis of important data that shows the importance of regional variability when evaluating risk of disease.

Click to read the study in the Lancet

Relevant Reading: Associations between BMI, waist circumference, central obesity and outcomes in type II diabetes mellitus: The ACCORD Trial

In-Depth [cross-sectional study]: This study used data from the WHO STEPS survey. If STEPS was not completed, a search was done for a suitable comparable survey done after 2008 with a 50% or higher response rate. In total, there were 58 surveys analyzed (9 non-STEPS) from 57 LMICs. Diabetes was defined as fasting plasma glucose > 7.0 mmol/L, random plasma glucose > 11.1 mmol/L, or a HbA1C > 6.5%. If no values were available, then the use of a diabetes medication was sufficient. The most used measurement to confirm diabetes was POC fasting glucose. A total of eligible 685 616 adults had data analyzed. Criteria included older than 25, complete diabetes status, BMI, sex and age. The mean age was 42.6 years and 52.8% were women. Pooled results showed 27.2% of adults were overweight, 21.0% obese and 9.3% had diabetes. The risk of diabetes was slightly higher in men (RR 1.05 vs. 1.04). The greatest increase in diabetes risk in terms of BMI category was seen in the upper-normal range (23.0-24.9) compared to normal (RR 1.41 in women, 1.43 in men). In individuals with a BMI > 30, risk increased steeply at age group 35-44 years, except for in men in sub-Saharan Africa which had increased risks at earlier ages of 25-34 years. Stratified regional analysis showed a variable BMI association with diabetes. Compared to normal BMI, the greatest risks for diabetes were observed in men with obesity from east, south, and southeast Asia (RR 3.93 [95 CI 3.18-4.86]) and sub-Saharan Africa (RR 3.46 [2.98-4.02]).

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