As the use of GLP-1 weight-loss drugs increases across England, researchers warn that limited attention to diet quality and nutrient intake could expose patients to overlooked health risks.
By Yasmina Perugia
Some people using popular weight-loss drugs may be at risk of nutritional deficiencies and muscle loss due to limited dietary support, according to researchers at University College London and the University of Cambridge.
The study, published in Obesity Reviews, found a lack of evidence-based guidance to ensure these medications are used safely and effectively.
The use of weight-loss drugs has risen sharply in recent years. Estimates suggest that around 1.6 million adults in England – roughly 2.9% of the population – used GLP-1 medications for weight management between early 2024 and early 2025.
Next-generation incretin therapies, including semaglutide and tirzepatide, mimic the hormone glucagon-like peptide-1 (GLP-1), which helps regulate appetite after eating. This effect can lead to marked reductions in food intake, with studies showing calorie reductions of between 24 and 39%.
While this appetite suppression contributes to weight loss, the researchers found that far less attention has been paid to its nutritional consequences. Few studies have examined diet quality, protein intake, or adequacy of micronutrients, a notable gap given that lean body mass, including muscle, can account for up to 40% of the total weight lost during treatment.
Dr Adrian Brown, an NIHR Advanced Fellow, Associate Professor in Nutrition and Dietetics at UCL’s Centre of Obesity Research, and senior author of the study, said: “What we know from these drugs is they considerably suppress appetite, they reduce energy intake, and they often result in rapid weight loss.” However, he added, “there's been a concern, particularly from the nutrition community, around people being nutritionally complete, i.e. getting enough protein, vitamins and minerals, and other essential nutrients”.
The researchers reviewed 12 studies and found limited systematic monitoring of patients’ nutritional status. In the available real-world data, 72% of patients consumed less energy than recommended, while more than 90% failed to meet daily requirements for multiple micronutrients, including vitamin D and potassium. Notably, only three of the studies involved dietitians, who, Dr Brown noted, “are the only profession regulated by law to deliver dietary advice.”
Independent experts say the findings reflect challenges already seen in clinical practice. Ivan Dozzani, a doctor specialising in clinical nutrition and obesity care, described the drugs as “potentially revolutionary” for people living with obesity, but warned that reduced food intake often leads to poorer diet quality if patients are not properly supported.
“If we change the management of obesity, we have to give solutions that are safe too,” Dozzani said, warning that a lack of nutritional guidance could risk “creating more malnutrition” rather than improving health.
While further evidence is needed before fully evidence-based dietary guidelines can be developed, the study highlights an urgent gap in current care. “We're really trying to show people that there are concerns. These drugs aren't necessarily the solution to everything; they’re not a wonder drug alone, there is a need for wrap-around care to support safe and sustainable use” Dr Brown said. As their use continues to expand, future research and clinical guidelines must place nutrition at the centre of obesity treatment, not as an optional add-on but as an essential component of care.
Research paper: Spreckley, M., Ruggiero, Cara F. and Brown, A. (2026). Nutrition Strategies for Next‐Generation Incretin Therapies: A Systematic Scoping Review of the Current Evidence. Obesity Reviews. https://doi.org/10.1111/obr.70079.
