Obesity Paradox: Better Survival in Obese Lung Cancer Patients with Strong Muscle Health, Study Finds

"In a study of more than 7,000 patients, those classified as obese (body mass index [BMI] ≥25) had a 21% lower risk of death compared to those without obesity (HR 0.79). This association was particularly strong among patients without low skeletal muscle mass or myosteatosis (HR 0.77)," the researchers reported.

The researchers note that a thorough evaluation of skeletal muscle health is essential to understanding the link between improved clinical outcomes and obesity, as defined by body mass index (BMI; calculated as weight in kilograms divided by height in meters squared), in lung cancer. However, there have been few studies exploring this relationship. To address this gap, Ji Hyun Lee, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea, and colleagues aimed to investigate the association between BMI-defined obesity and survival in patients with non-small cell lung cancer who underwent curative resection, with particular emphasis on skeletal muscle status assessed through CT imaging.

For this purpose, the researchers conducted a retrospective study on Korean non-small cell lung cancer patients who underwent curative resection between 2008 and 2019. Patients were categorized into nonobese (BMI <25) and obese (BMI ≥25) groups. Skeletal muscle status was assessed via CT scans at the level of the third lumbar vertebrae, with low skeletal muscle mass defined as the sex-specific lowest quartile. Cox regression analysis was performed to assess the associations between BMI, muscle status, and overall survival.

The research unveiled the following findings:

• The study included 7,076 patients, with a mean age of 62.5 years, of whom 4,081 were male. Of these, 35.5% had a BMI of 25 or greater, classifying them as obese.
• In patients without low skeletal muscle mass and myosteatosis, the obese group had longer overall survival compared to the nonobese group (HR 0.77).
• The association between obesity and lower mortality was observed only in male patients (HR 0.72).
• There was a lower mortality risk in patients who had ever smoked (HR 0.71) and had no LSMM or myosteatosis.
• The effect varied according to sex and smoking status, with P values ranging from <.001 to .02 for interaction.

The study identified a link between BMI–defined obesity and improved overall survival in patients with non–small cell lung cancer who underwent curative resection, provided that their CT-measured skeletal muscle mass and radiodensity were within normal ranges. The researchers suggest that while BMI is a useful and practical tool for initial assessment, it should be supplemented with detailed body composition measurements to deeply understand the obesity paradox in non–small cell lung cancer.

"The findings underscore the significance of the quantity and quality of skeletal muscle in explaining the relationship between obesity and improved survival. Further research exploring the biological mechanisms connecting preserved skeletal muscle status with better survival in individuals with obesity, particularly focusing on metabolic health, is essential," the researchers concluded.

Reference:

Lee JH, Kang D, Lee J, Jeon YJ, Park SY, Cho JH, Choi YS, Kim J, Shim YM, Kong S, Kim HK, Cho J. Association of Obesity and Skeletal Muscle with Postoperative Survival in Non-Small Cell Lung Cancer. Radiology. 2025 Jan;314(1):e241507. doi: 10.1148/radiol.241507. PMID: 39873605.