Obesity

Obesity

Obesity is a chronic disease recognized by every major medical organization. It is defined as a body mass index (BMI) of 30 kg/m2 or more and split into severity classes: Class I (BMI 30-34.9), Class II (BMI 35-39.9) and Class III or severe obesity (BMI ≥40). It results from a mix of genetic, environmental, behavioral and hormonal factors that create a lasting energy imbalance. It sharply raises the risk of type 2 diabetes, cardiovascular disease, obstructive sleep apnea, non-alcoholic fatty liver disease, osteoarthritis and many cancers.

Drug treatment for obesity was long held back by modest results and significant side effects. Incretin-based drugs changed that. GLP-1 receptor agonists showed that meaningful weight loss, defined as ≥5% of starting body weight, was possible in most treated patients. Retatrutide has gone further: in the Phase 2 trial, people on the highest dose lost an average of about 24% of their weight at 48 weeks, close to what is usually seen only with bariatric surgery.

Obesity is the main target of retatrutide’s clinical program. The Phase 3 TRIUMPH trials test its efficacy and safety in adults with obesity, or overweight with at least one weight-related condition. In TRIUMPH-1, published in the New England Journal of Medicine in September 2026, retatrutide 12 mg produced -28.3% mean weight loss at 80 weeks. If approved, retatrutide could be a major advance in obesity treatment: a once-weekly injection under the skin that delivers weight loss once possible only with surgery.