Overweight, obesity and weight loss: an umbrella review of meta-analyses on diets, behavioural programmes, medication, surgery and weight regain, 2013–2026

Background. Obesity is a chronic, relapsing disease driven by biological, psychological and social factors. Treatment options range from dietary and behavioural interventions to incretin-based medication and metabolic– bariatric surgery. Their effects have been summarised in numerous meta-analyses, but rarely compared side by side within a single evidence overview. Methods. Umbrella review of systematic reviews and meta-analyses of weight-loss interventions in adults with overweight or obesity, covering diets, behavioural programmes, pharmacotherapy, surgery, effects on mortality and weight regain after treatment cessation. Structured search of bibliographic records (PubMed/PMC, publisher and institutional repositories) up to 2 November 2026. Published pooled estimates were extracted without repooling; methodological features were appraised descriptively. Results. Eight meta-analyses (2013–2026) were included. Named diets produced weight losses of about 4 to 5.5 kg at six months compared with usual diet, with no clear superiority of any macronutrient pattern, and effects largely faded by twelve months. Behavioural programmes yielded –2.4 kg at 12 to 18 months, doubled the chance of losing at least 5% of body weight (RR 1.94) and reduced progression from prediabetes to diabetes by a third (RR 0.67). Placebo-subtracted weight loss was 16.2% with tirzepatide and 11.9% with semaglutide, compared with 3 to 9% for older drugs. Surgery produced 26 kg more weight loss than non-surgical treatment and was associated with 49% lower all-cause mortality and a median gain in life expectancy of 6.1 years. Across weight-loss trials, intentional weight loss reduced all-cause mortality (RR 0.82; high certainty). After stopping weight-loss medication, weight was regained at 0.4 kg per month, with return to baseline projected after 1.7 years, faster than after behavioural programmes. Conclusions. Effective treatments exist at every level of intensity, with a clear gradient of efficacy from diet and behavioural programmes to incretin-based medication and surgery. Because obesity is a chronic disease, durability is the central challenge: lifestyle-related losses fade and medication-related losses reverse after discontinuation. Long-term, stepped and combined treatment strategies, the preservation of lean mass and equitable access are the main open questions. Author. Dirk de Pol, Editor-in-Chief, MedizinDoc (medizindoc.de), Berlin, Germany