Sara Stanner, science director at the British Nutrition Foundation, explains why nutrition is central to supporting patients on weight-loss medications.
The rapid rise in the use of GLP-1 and GIP receptor agonists, such as Wegovy and Mounjaro, marks a shift in the treatment landscape for obesity care. As one of the UK’s leading causes of preventable illness, costing the NHS an estimated £6.5 billion annually, these medications can help people living with obesity to achieve clinically meaningful weight loss. For many patients, they represent a welcome shift towards recognising obesity as a chronic disease rather than a personal failing.
However, while 29 million people in England are eligible for treatment according to MHRA guidelines and 3.4 million under NICE guidance, it is estimated that only around 220,000 patients will be treated within the first three years. Meanwhile, a recent analysis by Nesta suggests that as many as 1.5 million people in the UK are already taking weight-loss medications. This means an estimated 90% of users are accessing treatments privately, potentially without sufficient clinical or nutritional support.
But while these medications can support weight loss, they do not directly address dietary quality, which is fundamental to improving health in both the short and long-term. Currently, for NHS patients, the window of opportunity to establish habits that support long-term wellbeing is limited as treatment is only offered for up to two years. In contrast, those accessing medication privately through online pharmacies may remain on the medication for longer, or even indefinitely. In both cases, dietary guidance is important.
At the British Nutrition Foundation, our position is clear: the success of weight-loss medications depends on sustained attention to a healthy, balanced diet, physical activity, and prioritising long-term behaviour change alongside medication.
Why appetite suppression can increase nutritional risk
Across the UK, intakes of fibre, calcium, folate, iodine, iron and vitamin A are already below recommended levels for many within the population. By design, weight-loss medications reduce hunger and slow gastric emptying, and lowered food intake risks exacerbating the problem of preexisting nutritional inadequacies. Lean mass, such as muscle and bone, can account for a clinically important proportion of weight loss when taking these medications. Preserving muscle mass by prioritising protein and exercise is therefore crucial, not just for metabolic health, but to support long-term weight management once treatment ends.
More concerningly, these risks are not experienced equally across all users, so tailored advice is required for certain groups who may need additional consideration. Older adults, for example, may be more vulnerable to muscle and bone loss and therefore need particular emphasis on protein, calcium and vitamin D. Separately, women of reproductive age may already be at risk of inadequate intakes of folate, iodine and iron, and therefore require a focus on these nutrients which are important for their own health, as well as for future pregnancies. It should be noted, however, that use of weight-loss medications is not approved for pregnant women, and these medications should not be used when trying to conceive or during breastfeeding.
Another emerging concern is the number of people accessing weight-loss medications privately, through unregulated online sources or while abroad, without regular clinical monitoring, potentially missing out on key guidance on nutrition, hydration, and long-term behaviour change. Ensuring these groups receive clear, evidence-based advice is important for reducing the risk of nutritional inadequacy, coping with side effects such as constipation and nausea, and for setting up healthier habits that can be sustained over the longer term.
What healthcare professionals can do
Evidence shared through our recent webinars and guidance highlights several practical priorities for healthcare professionals supporting patients on weight-loss medications:
First, they focus on fibre intake. Most UK adults do not meet the 30g per day target for dietary fibre. Smaller portion sizes may make it more difficult to achieve these targets, affecting gut health and potentially increasing the risk of longer-term, diet-related diseases. Suggest to patients that they gradually include more wholegrain carbohydrate foods, fruit and vegetables, beans and lentils, nuts and seeds. Reassure them that fibre, alongside sufficient fluid intake, also helps reduce constipation, which is a common side effect for weight-loss medication users.
Next, they prioritise protein in every meal. A reduction in appetite, resulting in, for example, meal skipping, may mean users struggle to consume enough protein to maintain muscle mass. Encourage patients to include a source of protein, such as fish, lean meat, eggs, or pulses, across mealtimes and to undertake strength-based activity, where possible, to support muscle preservation. Strength training twice a week is recommended for all UK adults.
At the same time, they support micronutrient adequacy. Certain nutrients like iron, iodine, calcium, folate, and vitamin A intakes are often low in UK diets. Including a variety of nutrient-dense foods such as dairy products or fortified alternatives, wholegrain and fortified cereals, vegetables and fruits and a wide variety of protein-rich foods, such as beans, fish, eggs and lean meats, can help to ensure that nutrient requirements are met.
They also reinforce hydration and digestive comfort. Fewer eating occasions and lower food consumption could also result in lower fluid intake, increasing constipation and fatigue. Encouraging regular sips of water throughout the day, carrying a water bottle and having regular drinks, including unsweetened regular or herbal tea or coffee, can help to avoid unintentional dehydration.
Finally, they use structured behaviour-change approaches: Use patient-centred counselling methods, such as the 5A’s (Assess, Advise, Agree, Assist and Arrange) framework, to encourage behaviour change, providing constructive, non-judgemental conversations about diet and lifestyle. Try introducing staged changes, as some early success with weight loss can build confidence before gradually introducing more detailed dietary advice and goals.
A moment of opportunity
Weight-loss medications can provide a lifeline, supporting patients to break the cycle of repeated weight loss and gain, but only when paired with sustained, evidence-backed nutritional guidance and advice. The core message remains constant across all healthcare applications – weight-loss medications should complement, not replace, a healthy, balanced diet and lifestyle.
At the British Nutrition Foundation, we remain committed to providing credible, evidence-based information for healthcare professionals navigating this fast-moving field. With coordinated support, weight-loss medications can become not just a weight-loss tool, but a catalyst for lasting improvements in diet, metabolic health and quality of life.
