Weight Loss Medication – what is the truth?

With weight loss medications dominating headlines and social feeds almost daily, separating fact from fiction has never been trickier. One thing’s for sure: these so-called “wonder drugs” are capturing the public’s attention like never before. 

In this article, Dr Chris Cashin, Programme Manager in Sport and Excercise Nutrition at UWTSD, cuts through the hype to explore what’s really behind the buzz.

There has been a lot of interest in weight loss medication over recent months and it does seem that many people are taking them to lose weight. 

There are a number of so called weight loss medications that are collectively known as GLP – 1RA’s (Glucagon like peptide 1 receptor agonists). The most commonly used are Wegovey / Ozempic (Semaglutide) and Mounjaro (Tirzepatide).

They were initially developed to treat Type 2 Diabetes but after clinical trials showed many of the participants had lost around 10% of their body weight, attention turned to their use in weight management. 

How do they work?

GLP-1 is a hormone that is produced in the stomach after you eat. Its main role is to regulate your appetite by acting on the brain’s hypothalamus to reduce appetite and increase satiety (fullness). It also aids the control of blood glucose (sugar) levels by increasing insulin levels. Therefore, it helps to control weight and decrease appetite. There are also some other health improvements reported in clinical trials, such as reducing cardiovascular risks and improving fatty liver disease.

The drugs are known as agonists or mimics, as they make the body think there is more GLP-1 available to control the appetite.

They are taken by weekly injections subcutaneously, usually into the abdomen, thigh or arm in a pre-filled pen. 

Is it available on the NHS?

GLP-1RA’s are available in England and Wales on the NHS but there are strict criteria, such as a high BMI (>40), plus patients need to have other co-morbidities, such as Type 2 Diabetes and cardiovascular disease. You will need to have a BMI (Body Mass Index) of more than 27 -3,0 depending on any other conditions such as heart disease or high blood pressure.

In Wales it is usually prescribed by specialist weight management services within each health board.

As it is limited on the NHS it is easy to understand why so many people are now obtaining the medication through online pharmacies at quite a cost to themselves. It is worth noting that from wherever you obtain the medication, you still need to meet the criteria such as higher Body Mass Index and certain health conditions, in order to be prescribed them. It is certainly worth noting that reputable online pharmacies or suitably qualified health care practitioners are the safest places to obtain the medication. It is estimated that around 1.5 million people are currently taking a weight loss medication via private prescription. 

Are there any side effects?

Most people do have some degree of side effects such as nausea, gastrointestinal issues, constipation, low blood glucose when taking some diabetes medications, headaches and, in more severe cases, pancreatitis. It is important to seek medical advice if suffering from any of these side effects.

Do I need to change my lifestyle?

The simple answer is Yes – it may affect your appetite, but if you stop the medication, the evidence suggests that most people do put weight back on unless they change their diet and physical activity. As a Nutritionist and Dietitian, what I am seeing in practice is that many people are not getting adequate advice on what to eat and how to be active.

Nutrition

Many people who are taking these weight loss medications do not seem to get adequate nutrition advice when they are prescribed, plus there are so many so called experts on social media offering nutrition advice that may not be based on evidence. The usual method of weight loss is to follow a plan that creates a calorie deficit. These days, Dietitians and Nutritionists do not usually prescribe very low calorie diets, but it does seem that many people are reporting eating very small amounts of food. This is not healthy as it can lead to deficiencies of important minerals and vitamins, and muscle loss.

There are some important things to consider, such as:-

• Eat a helping of protein at meals – this can be chicken, meat, eggs, cheese or fish, but also vegetarian sources such as Tofu or beans. 
• Eat your five a day – 2 portions of fruit and the rest as vegetables. If you can eat more than the 5 helpings of vegetables, evidence shows it can really help to improve the gut microbiome.
• Keep to wholegrain carbohydrates such as wholemeal bread/pasta/cereals, and potatoes with their skins on.
• Use small amounts of fats such as butter/ margarine and olive oil.
• Drink enough fluid – water, tea, coffee and sugar free drinks – most people need 2 – 2.5 litres in total.
• Include at least 300mls (half a pint) of dairy such as milk or yoghurt, but if you cannot eat dairy, use a plant based drink that has added calcium to protect your bones.

Physical Activity

The UK guidelines state that we should all aim for 150 minutes of aerobic exercise per week which could be walking, running or classes that are active. We should also include 2  x 30 minute sessions of resistance exercise – yes, that does mean weight training! It is probably a good idea to get some professional advice as it is important to do this in the correct manner.

Conclusion

The weight loss medications can certainly help you to decrease your weight, but a healthy diet and exercise are very important as well. If you are not getting advice from the medication provider, it is definitely worth seeking advice from a Registered Nutritionist (Association for Nutrition) and avoiding much of the poor information that is so readily available across a range of social media channels.

References

Garvey, W.T., Mechanick, J.I., Brett, E.M., Garber, A.J., Hurley, D.L., Jastreboff, A.M., Nadolsky, K., Pessah-Pollack, R. and Plodkowski, R. (2016) ‘American Association of Clinical Endocrinologists and American College of Endocrinology comprehensive clinical practice guidelines for medical care of patients with obesity’, Endocrine Practice, 22, pp. 1- 203.

GovUK (2019) Physical Activity Guidelines for the United Kingdom. Available at: https://www.gov.uk/government/publications/physical-activity-guidelines-uk-chief-medical-officers-report

Kaplan, L.M., Apovian, C.M., Ard, J.D., Allison, D.B., Aronne, L.J., Batterham, R.L., Busetto, L., Dicker, D., Horn, D.B. and Kelly, A.S. (2024) ‘Assessing the state of obesity care: Quality, access, guidelines, and standards’, Obesity Science & Practice, 10(4), pp. e765. 

Mechanick, J. I., Butsch, W. S., Christensen, S. M., Hamdy, O., Li, Z., Prado, C. M., & Heymsfield, S. B. (2025). Strategies for minimizing muscle loss during use of incretinmimetic drugs for treatment of obesity. Obesity Reviews, 26(1), e13841.

Further Information

Lowri Thomas

Principal Communications and PR Officer     
Corporate Communications and PR     
Email: lowri.thomas@uwtsd.ac.uk     
Phone: 07449 998476