When weight loss drugs work, don’t let nutrition and muscle fall behind

Clinical takeaway: Adults receiving GLP-1 or dual GLP-1/GIP therapies should be monitored not just for weight loss, but also for nutritional adequacy, gastrointestinal intolerance, muscle function, psychological adjustment, and signs of malnutrition—especially if weight loss is rapid or intake is very low.

Incretin-based therapies such as semaglutide and tirzepatide have reshaped obesity care, but a new EASO*/EFAD*/ECPO* consensus statement warns that appetite suppression and rapid weight loss can create risks that BMI alone will miss.

The statement emphasizes dietitian-led medical nutrition therapy, particularly for patients with nutritional risk, older age, frailty, restrictive diets, food insecurity, prior bariatric surgery, chronic disease, persistent GI symptoms, or excessive weight loss. Practical targets include protein of about 1.0–1.5 g/kg adjusted body weight per day during active weight loss, with at least 60 g/day; fiber of at least 25 g/day; fluids of about 2.0–2.5 L/day unless contraindicated; and nutrient-dense foods rather than routine reliance on supplements.

Drug-related guidance focuses on tolerability and safety. Clinicians should use gradual dose escalation, and if significant nausea, vomiting, or other GI effects occur, consider delaying titration, returning to the last tolerated dose, temporarily pausing therapy, or discontinuing when clinically necessary. Persistent vomiting should prompt urgent review, hydration and nutrition assessment, possible thiamine supplementation, and consideration of dose reduction or interruption.

The authors also call for screening for disordered eating, alcohol misuse, mood symptoms, and psychological vulnerability when clinically indicated. Access to incretin therapy should not be routinely delayed solely because of severe mental illness, but monitoring and shared care should be adapted.

Because 24%–30% of weight lost in trials may be fat-free mass, the consensus recommends moving beyond BMI to include waist measures and simple function tests such as handgrip strength or five-times sit-to-stand. Resistance training and adequate protein are highlighted as key strategies to help preserve lean mass.

“Incretin-based therapies represent a paradigm shift in obesity care,” the authors write, but optimal use requires “dietitian-led medical nutrition therapy with integrated psychological and functional support.”

*EASO: European Association for the Study of Obesity; EFAD: European Federation of the Associations of Dietitians; ECPO: European Coalition for People Living with Obesity.

Source: Dobbie LJ, et al. (2026 July 8) Lancet Diabetes Endocrinol. Nutritional, functional, and psychological considerations for incretin-based therapies in adults—an EASO, EFAD, and ECPO Consensus Statement