Science identifies biological drivers behind obesity and weight regain

Medical science is increasingly characterizing obesity as a complex, chronic disease driven by biological mechanisms rather than a simple lack of willpower or discipline. When individuals lose weight through strict dieting, the body often perceives the loss as a threat, triggering defense mechanisms such as increased appetite, a reduced metabolic rate, and altered satiety hormones. This biological response contributes to the “rebound effect,” with research suggesting that approximately 80% of people regain lost weight within three years.

Recent studies, including research conducted by Japanese scientists on mice, suggest that the body may “remember” obesity at a cellular level. This research focused on adipose tissue macrophages (ATMs)—immune cells in fat tissue that regulate inflammation and fat levels. The study found that obesity causes changes in these cells related to mRNA splicing that do not reverse even after weight loss. Specifically, mice that struggled to maintain a healthy weight exhibited low levels of a protein called CWC22, which is involved in the protein synthesis process. While these findings in mice require further study to determine if they are directly extrapolatable to humans, they provide insight into why maintaining weight loss is biologically challenging.