Obesity and type 2 diabetes mellitus (T2DM), which often coexist as 'diabesity,' are chronic conditions with lifelong implications for health, quality of life, and healthcare systems worldwide. Lifestyle interventions, including dietary modifications, physical activity, and behavioral strategies, are widely recommended as first-line treatment. However, evidence across systematic reviews varies in methodological quality and conclusions. This umbrella review synthesizes high-level evidence to guide sustainable, non-pharmacological strategies for managing obesity in adults with T2DM across the lifespan.

A systematic search of SCOPUS, PubMed, Web of Science, and ProQuest identified 382 records. After screening, seven systematic reviews were included, four of which conducted meta-analyses. Eligible reviews included adults aged 18 years and older with coexisting obesity and T2DM, and evaluated lifestyle interventions compared to any comparator. Interventions were categorized thematically. Methodological quality was appraised using the AMSTAR-2 tool.

Multicomponent interventions demonstrated the most clinically significant effects, including at least 5% weight loss, reductions in HbA1c ranging from 0.3 to 1.0%, and improvements in cardiometabolic markers. Cognitive behavioral therapy further supported adherence and self-management. While single-component dietary or physical activity interventions yielded moderate benefits, multicomponent strategies showed more sustained impact. Gaps remain in standardized outcome reporting, long-term follow-up, and inclusion of patient-centered outcomes such as quality of life and functional capacity.

Lifestyle interventions, particularly those combining dietary, physical activity, and behavioral components, are effective and sustainable strategies for managing obesity in adults with T2DM. These findings highlight the importance of a lifelong, behavior-focused approach to diabesity care. Future research should emphasize standardized outcomes, cultural adaptation, and implementation across diverse populations and healthcare systems.