Mixed
Maintaining a BMI between 21 and 25 kg/m² is associated with the lowest risk of all-cause and cause-specific mortality (including cancer, cardiovascular, and respiratory diseases) in never-smokers, whereas obesity (BMI ≥30) reduces life expectancy by 3.5–4.2 years compared to healthy weight.
For long-term health and longevity, aim for a BMI between 21 and 25 kg/m². This range is associated with the lowest risk of death from major diseases like cancer and heart conditions. While being 'overweight' (BMI 25-29.9) is not as dangerous as obesity, this study indicates that health risks start to climb once you exceed 25. Avoiding being underweight (<18.5) is equally critical for maximizing life expectancy.
Most causes, including cancer, cardiovascular diseases, and respiratory diseases, had a J-shaped association with BMI, with lowest risk occurring in the range 21–25 kg/m²... life expectancy from age 40 years was 4·2 years shorter in obese (BMI ≥30·0 kg/m²) men and 3·5 years shorter in obese women... and 4·3 years shorter in underweight (BMI <18·5 kg/m²) men and 4·5 years shorter in underweight women.
Why this rating
Large-scale population cohort (3.6 million adults) with rigorous adjustment for confounders (smoking, age, deprivation) and sensitivity analyses.
Source
Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3·6 million adults in the UK
Krishnan Bhaskaran et al. · The Lancet Diabetes & Endocrinology · 2018
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