High body mass index within the normal weight range and risk of type 2 diabetes and hypertension in US and Europe: a systematic review and meta-analysis.

Abstract

Clinical guidelines suggest body mass index (BMI) thresholds of ≥25 kg/m² to identify individuals at elevated risk of type 2 diabetes and (T2D) hypertension, however, growing evidence suggests that higher BMI values within the normal weight range may also be associated with increased risks. A systematic search was conducted in PubMed and Scopus, with an updated PubMed search through October 2025, to identify cohort studies from the US and Europe that reported risk estimates of T2D or hypertension for higher normal weight BMI values (e.g., 22.5-24.9 kg/m²) compared with lower normal weight BMI values. Asian studies were excluded because of lower BMI thresholds in Asian populations. Random-effects meta-analysis was performed to estimate summary relative risks (RRs) and 95%CIs. Eleven cohort studies were included, with 23% of participants and 17% of cases being classified as having high normal weight BMI values (22.5-24.9 kg/m²). Compared with lower BMI values within the normal weight range, high normal weight BMI values were associated with a greater risk of T2D (RR = 1.78, 95% CI: 1.30-2.45, I² = 98%; n = 10 studies with 1,818,036 participants and 84,414 cases; moderate certainty evidence). Evidence for hypertension was limited, based on three US cohort studies (RR = 1.42, 95% CI: 1.33-1.51, I² = 0; n = 3 studies with 129,046 participants and 22,254 cases; low certainty evidence). Compared with lower normal weight BMI values, higher BMI within the normal range was associated with a higher risk of T2D and hypertension, suggesting that current BMI classifications may not fully capture the increased risk among individuals at the upper end of the normal weight spectrum. If replicated, the findings may justify reconsideration of BMI thresholds to better reflect the higher cardiometabolic risk observed among individuals with high normal weight BMI.