Newer weight loss medications have helped many people lose a large amount of weight in a short time.
Drugs such as semaglutide and tirzepatide have quickly become popular, both through medical prescriptions and private clinics.
However, experts from University College London and the University of Cambridge are now warning that many people using these drugs may not be getting enough nutrition guidance to stay healthy in the long term.
Without proper support, users may face avoidable problems such as vitamin and mineral deficiencies and loss of muscle mass.
These concerns come from a new study published in the journal Obesity Reviews. The research was led by Dr. Marie Spreckley from the University of Cambridge and examined how nutrition advice is currently provided to people using these medications.
The team found that there is very limited high-quality evidence on how dietary guidance affects calorie intake, muscle mass, protein intake, and overall patient experience during treatment. This gap is worrying, given how widely these drugs are now being used.
To understand the issue, it helps to know how these medications work. Drugs such as semaglutide and tirzepatide are often sold under brand names like Ozempic, Wegovy, and Mounjaro. They work by copying the effects of a natural hormone called GLP-1, which the body releases after eating.
This hormone helps control appetite by increasing feelings of fullness and reducing hunger and food cravings. As a result, people taking these drugs often eat much less than before.
Studies show that calorie intake can drop by around 16 to 39 percent while using these medications. This strong appetite-suppressing effect makes the drugs very effective for weight loss and can improve conditions such as type 2 diabetes and heart disease.
However, the researchers point out that eating less does not automatically mean eating better. Very little research has looked closely at whether people on these drugs are getting enough protein, vitamins, and minerals to support their bodies.
One major concern is the loss of lean body mass, which includes muscle. Existing evidence suggests that as much as 40 percent of the total weight lost during treatment may come from lean tissue rather than fat. Losing muscle can reduce strength, slow metabolism, and increase the risk of falls and injuries, especially in older adults.
Dr. Adrian Brown from UCL, the study’s corresponding author, explained that while appetite suppression is a key benefit of these medications, it also creates risks. When people eat far less food, their overall diet quality can suffer.
Without guidance from healthcare professionals, individuals may not consume enough protein, fiber, or essential vitamins and minerals needed for long-term health.
In the UK, national guidelines from the National Institute for Health and Care Excellence recommend semaglutide for weight management only for people who meet strict criteria, such as having a high body mass index and related health conditions.
When prescribed through the National Health Service, the medication is meant to be part of a broader program that includes a reduced-calorie diet, physical activity, and ongoing support.
In reality, most people using these medications do not access them through the NHS. Around 1.5 million people in the UK are estimated to be taking GLP-1 weight loss drugs, and about 95 percent obtain them privately.
In many private settings, follow-up appointments and structured nutrition advice are limited or completely absent. This means many users are left to manage major changes in eating habits on their own.
Dr. Spreckley noted that the rapid rise in use has far outpaced the development of proper nutritional care. Many people experience strong appetite suppression but receive little guidance on how to maintain a balanced diet.
Without support, there is a real risk of trading obesity-related health problems for new ones caused by poor nutrition. Low intake of key nutrients can lead to fatigue, hair loss, weakened immune function, and bone loss, while muscle loss can reduce physical function and independence.
The researchers reviewed existing studies and found only 12 that examined diet and nutrition alongside treatment with semaglutide or tirzepatide. These studies varied widely in quality and methods, making it difficult to draw clear conclusions or provide firm recommendations. This lack of evidence leaves doctors and patients without clear guidance.
Because of this gap, the researchers suggest borrowing lessons from nutrition care used after weight loss surgery. After bariatric surgery, patients receive structured advice to prioritize nutrient-dense foods and adequate protein intake. These principles may also help people using weight loss drugs preserve muscle and avoid deficiencies.
The study did not support strict low-fat diets alongside these medications. However, some studies showed that users may consume high levels of total and saturated fat, suggesting that personalized advice could be useful. Meal timing was also rarely studied, but eating smaller meals more frequently may help reduce side effects such as nausea.
In reviewing the findings, the study makes one message clear: weight loss drugs are powerful tools, but they are not complete solutions on their own. Without proper nutrition guidance, their benefits may come at the cost of long-term health.
As use continues to grow, integrating nutrition care into treatment is essential. Doing so could help people lose weight safely, protect muscle mass, and support lasting improvements in health rather than short-term success followed by new problems.
If you care about weight loss, please read studies that hop extract could reduce belly fat in overweight people, and early time-restricted eating could help lose weight .
For more health information, please see recent studies about a simple path to weight loss, and results showing a non-invasive treatment for obesity and diabetes.
Copyright © 2026 Knowridge Science Report. All rights reserved.
