Global Experts Warn Against Using Weight-Loss Injections Without a Dietician

Millions of people using popular weight-loss injections may be losing more than unwanted fat unless their treatment is backed by expert nutritional care, according to a landmark international consensus statement published in The Lancet Diabetes & Endocrinology. The guidance urges patients not to rely on medicines alone, warning that without proper diet, exercise and monitoring, they could lose valuable muscle, develop nutritional deficiencies or overlook emerging mental health concerns.

The recommendations were developed by an international panel of 26 experts led by Dr Laurence Dobbie of King's College London, in collaboration with the European Association for the Study of Obesity (EASO), the European Federation of the Associations of Dietitians (EFAD) and the European Coalition for People Living with Obesity (ECPO).

The statement focuses on incretin-based therapies, including widely used GLP-1 receptor agonists—medicines that mimic a natural gut hormone to reduce appetite, slow stomach emptying and help people feel full for longer. While these drugs have transformed obesity treatment and helped many patients achieve meaningful weight loss, experts say they are only one part of successful long-term care.

An analysis of existing clinical trials cited in the statement found that 24–30% of the weight lost with these medicines may come from fat-free mass, mostly muscle rather than fat. Muscle plays a vital role in movement, balance, metabolism and healthy ageing, making its loss particularly concerning for older adults who already have lower muscle reserves.

The experts suggest a practical target: for every four kilograms lost, at least three kilograms should come from body fat and no more than one kilogram from muscle and other fat-free tissue. Achieving that balance, they stress, requires far more than an injection.

Medical Nutrition Therapy, which is usually delivered by a registered dietician, is described as central to obesity care. Dieticians help patients consume enough protein, vitamins, minerals, fibre and fluids, manage common digestive side effects and support lasting dietary habits.

The authors also recommend regular resistance training—strength-building exercises, such as lifting weights or using resistance bands—to help preserve muscle while losing weight, alongside aerobic activity.

Monitoring should also move beyond the familiar Body Mass Index (BMI). Experts recommend measuring waist size, testing muscle strength with simple tests, like handgrip strength or repeated chair stands, and, where available, using body composition scans, such as dual-energy X-ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA) to differentiate fat loss from muscle loss. These tests give a better picture of the overall health of the body and not just the weight.

The consensus statement also considers the psychological aspects of obesity treatment. Weight loss can make many people feel better, but significant changes in the body can also lead to emotional difficulties or a recurrence of prior mental health problems. The authors recommend mental health assessment and screening for alcohol-use disorders prior to beginning GLP-1 therapy, along with ongoing support from multidisciplinary care teams.

Disadvantaged communities are disproportionately affected by obesity, the researchers note, and often face more barriers to specialist care, including access to dieticians and newer medicines. They say that better access to comprehensive obesity services could improve outcomes and help reduce the continuing stigma around obesity being a chronic disease.

The authors conclude: “IBTs are a paradigm shift in obesity care, optimal implementation consists of dietician-led medical nutrition therapy with integrated psychological and functional support.” They add that preventing vitamin deficiencies, protecting muscle and bone, managing side effects and supporting patients’ emotional wellbeing should all become standard parts of treatment.

The writer is a Delhi-based freelancer who writes on health issues and medical discoveries.