“Obesity is a much more complex disease than previously understood. It is more than a simple lack of willpower, laziness, or a refusal to ‘eat less and move more’. The root causes of obesity run much deeper.” (Ballesteros-Pomar and Barazzoni, 2026)
The National Institutes of Health (NIH) first declared obesity a chronic disease in 1998. The American Medical Association followed suit in 2013, and in 2021, the European Commission called obesity a “chronic relapsing disease.” Despite these organizations recognizing that carrying excess body fat is not a character flaw—not a failure of willpower and discipline—social debates continue, with many wanting to make obesity no more complicated than simple greed and sloth.
A recent paper in Clinical Nutrition ESPEN (the European Society for Clinical Nutrition and Metabolism) dives deep into the biological underpinnings of obesity and provides a comprehensive overview of the many contributing factors to obesity , such as problems with appetite regulation, chronic stress, altered circadian rhythms, endocrine-disrupting chemicals, and more. It also reiterates the shortcomings of the body mass index (BMI) and places more emphasis on body composition and waist-to-height ratio, which may be stronger indicators of metabolic health compared to body weight alone.
By acknowledging the myriad factors that can influence weight and eating behaviors, this review shifts “blame” away from the individual and focuses more on societal and systemic changes that may be more effective for addressing obesity than simply advising people to eat less, while still recognizing that individual agency plays a role. The authors propose that we have entered an era of seeing the complexity in obesity. Rather than merely a simplistic imbalance in calories taken in and calories expended, they describe the current era as one in which obesity is “recognized as a tremendously complex chronic disease integrating social, environmental, genetic, and metabolic determinants.”