Experts warn weight loss drug users in the UK risk nutritional deficiencies without proper support
Cambridge study highlights lack of structured dietary guidance for those using medications such as Ozempic
Last updated 8th Jan 2026
People using weight loss drugs like semaglutide and tirzepatide—marketed as Ozempic, Wegovy and Mounjaro—may face nutritional deficiencies and muscle loss due to insufficient dietary advice and support, experts from UCL and the University of Cambridge have warned.
A study published today in Obesity Reviews has found limited evidence surrounding nutritional guidance for people taking these drugs. According to the researchers, who analysed available studies, there could be risks of poor protein intake, lack of essential vitamins and minerals, and lean muscle loss linked to reduced calorie consumption during treatment.
Dr Adrian Brown from UCL said that while these medications effectively suppress appetite and promote substantial weight loss, “without appropriate nutritional guidance and support from healthcare professionals, there is a real risk that reduced food intake could compromise dietary quality.”
The National Institute for Health and Care Excellence (NICE) guidelines recommend semaglutide as part of an NHS programme that includes a reduced-calorie diet and increased physical activity for those meeting specific criteria, such as a body mass index (BMI) of at least 35 and related conditions like type 2 diabetes. However, most people—around 95% of the estimated 1.5 million GLP-1 drug users in the UK—access the medication privately, where additional nutritional advice is often missing.
Dr Marie Spreckley from the Medical Research Council at the University of Cambridge is leading research into the impact. She said that nutritional care has not kept pace with the rapid rise in usage of these medications, creating risks of preventable deficiencies and muscle loss.
While the researchers acknowledged the need for more targeted studies to inform nutritional support, they suggested interim guidance could be drawn from established practices surrounding weight loss surgeries like gastric bands, which have similar outcomes to GLP-1 drugs.
Dr Cara Ruggiero, co-author of the study, pointed out the importance of prioritising nutrient-dense foods, including protein, distributed evenly across meals to maintain lean muscle mass during rapid weight loss.
She added that strategies like small, frequent meals could help reduce common side effects such as nausea and improve tolerability, especially in early treatment stages.
The team has launched the AMPLIFY project to better understand how people experience these therapies, focusing on diverse perspectives. Dr Spreckley explained, “These medications are transforming obesity care, but we know very little about how they shape people’s daily lives. That’s what we’ll explore, especially with people from communities historically under-represented in obesity research.”
The study was funded by the National Institute for Health and Care Research (NIHR), with support from the NIHR UCLH Biomedical Research Centre and the Medical Research Council.