Research
Mixed
The association between low BMI and increased mortality is likely caused by preclinical disease (weight loss preceding diagnosis) rather than low body weight itself.
If you are underweight, do not panic about mortality risk based on BMI alone. This risk is often driven by underlying undiagnosed health issues causing weight loss. Focus on medical check-ups rather than just trying to gain weight.
WeakRefutesHIGH confidence
The increased risk of mortality observed in underweight people could at least partly be caused by residual confounding from prediagnostic disease.
Why this rating
Supported by stratification by follow-up duration showing risk decreases with longer follow-up.
Source
BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants
Dagfinn Aune et al. · BMJ · 2016
DOI 10.1136/bmj.i2156
Meta-analysis · 230 studiesCited 956×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
Related findings · Mixed
- Bariatric surgery (VSG and RYGB) is the most effective and sustainable treatment for obesity, producing marked and sustained weight loss that non-surgical interventions cannot match.Strong
- Severely protein-deficient diets (2–3% energy) induce lean body mass loss and metabolic imbalance, whereas adequate protein intake (0.66 g/kg/d minimum) is a prerequisite for maintaining muscle, bone, and physiological function.Strong
- For patients with Class III obesity (BMI >39.9 kg/m2), metabolic bariatric surgery (MBS) is significantly more effective than any currently approved medication, with BilioPancreatic Diversion (BPD) showing the highest estimated weight loss.Strong
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