A study found that overweight and obese individuals have a 0.7 times lower risk of suicide compared to those with a normal weight, while underweight individuals have a 1.44 times higher risk.
Professor Lee Seung Hwan and his team from the Department of Endocrinology at Seoul St. Mary’s Hospital, Catholic University, analyzed the relationship between BMI (Body Mass Index) and suicide risk in over 4 million individuals registered in the National Health Insurance Corporation database.
The study considered various factors, including age, gender, income, lifestyle habits like smoking and drinking, exercise routines, mental health issues, and the presence of chronic diseases such as diabetes.
Results showed that the underweight group (BMI < 18.5 kg/m²) had a 1.44 times higher risk of suicide than the normal weight group (BMI 18.5–23 kg/m²). This group also showed higher prevalence rates of diabetes, hypertension, dyslipidemia, and chronic kidney disease. Women accounted for 66.74% of the underweight group, with 70.38% being non-smokers and 56.88% non-drinkers.
Conversely, suicide risk decreased as BMI increased. The overweight group (BMI 23–25 kg/m²) had a 0.79 times lower risk, the obese class 1 group (BMI 25–30 kg/m²) had a 0.76 times lower risk, and the obese class 2 group (BMI > 30 kg/m²) had a 0.71 times lower risk.
However, these findings were independent of factors such as major depressive disorder, housing conditions, and lifestyle habits.
The researchers explained: “Leptin, a hormone produced by fat tissue, signals the brain to regulate hunger and energy balance. Obesity reduces the brain’s response to leptin. This increased leptin resistance can alter the brain’s reward processing pathways, potentially reducing impulsivity in certain situations.”
They also highlighted the psychological factors at play: “Issues like body image concerns, victimization, bullying, eating disorders, and sleep problems might be connecting the dots between suicide risk and being underweight. To effectively reduce future suicide rates, public health resources should be strategically allocated, and policymakers must carefully assess where to invest.”
The study was published in the January issue of the international journal BMC Psychiatry.