section_path: Effects on health/Mortality
section_name: Mortality
paragraph_text: Mortality
  
  Obesity is one of the leading preventable causes of death worldwide. The mortality risk is lowest at a BMI of 20–25 kg/m in non-smokers and at 24–27 kg/m in current smokers, with risk increasing along with changes in either direction. This appears to apply in at least four continents. Other research suggests that the association of BMI and waist circumference with mortality is U- or J-shaped, while the association between waist-to-hip ratio and waist-to-height ratio with mortality is more positive. In Asians the risk of negative health effects begins to increase between 22 and 25 kg/m. In 2021, the World Health Organization estimated that obesity caused at least 2.8 million deaths annually. On average, obesity reduces life expectancy by six to seven years, a BMI of 30–35 kg/m reduces life expectancy by two to four years, while severe obesity (BMI ≥ 40 kg/m) reduces life expectancy by ten years.