A guide to medicated weight loss

Niamh Hennessy
Lead Dietitian, Cromwell Hospital
05 January 2024
Next review due January 2027

Have you heard about weight loss injections? Whilst they’re not suitable for everyone, there’s evidence to suggest that some people may benefit. Here, I’ll explore what medicated weight loss is, who it’s suitable for, and what the potential side-effects are.

Two people running up some stairs

What is medicated weight loss?

The phrase ‘medicated weight loss’ usually refers to two different types of treatments. These are weight loss pills and weekly weight loss injections. Medicated weight loss is now an option for people who meet certain criteria and may be suggested as an alternative option to weight loss (bariatric) surgery.

One type of medication often used in weight loss pills and injections is called semaglutide. Semaglutide belongs to a class of medications called glucagon-like peptide 1 receptor agonists. These medications have various effects in the body and may support weight loss.

Some weight loss medications include orlistat and setmelanotide. These work in a different way but may also help you to lose weight.

How does medicated weight loss work?

Semaglutide, which is used in the weight loss injection Wegovy, affects a part of your brain linked to appetite and fullness. This means you’ll feel less like eating. You’ll also become full more quickly. So, you end up eating less, which reduces your calorie intake, and therefore promotes weight loss.

Orlistat, another weight loss medication, reduces the amount of fat you absorb from your food, which can also help you to lose weight.

Who is eligible for medicated weight loss?

Currently there are quite strict criteria for who can use medicated weight loss treatments. For example, with Wegovy, you would usually need to have a body mass index (BMI) of 30 or higher. You might also be prescribed Wegovy if you have a BMI between 27-30, but you must also have an additional weight-related health issue, such as type 2 diabetes or high cholesterol.

A doctor will also need to check your medical history. This is to make sure you don’t have any health issues that would make you unsuitable for medicated weight loss. These could include stomach issues, kidney disease, or heart failure.

What are the benefits of medicated weight loss?

Current evidence shows that combining weight loss medications with lifestyle changes is a more effective way to lose weight than just making lifestyle changes on their own. In one study, most participants taking semaglutide lost 5-10 per cent of their body weight.

Some weight loss medications can also lower your blood sugar and cholesterol levels. This can reduce the risk of heart disease and type 2 diabetes.

What are the side effects of medicated weight loss?

Most side-effects are mild, and usually go away once you’ve been taking the medication for a little while. They can include things such as:

  • feeling or being sick
  • constipation
  • diarrhoea
  • stomach-ache
  • headache
  • tiredness

Some of these minor side effects may be prevented. You can reduce your risk of experiencing these side effects by:

  • reducing your portion sizes
  • eating mindfully and stopping when full
  • avoiding high fat or spicy foods
  • reducing alcohol intake
  • drinking plenty of fluids

Occasionally, more serious side-effects can occur, so report any new symptoms to a doctor straight away.

Are lifestyle changes important with medicated weight loss?

Lifestyle changes are the key to success when using weight loss medications. This is true both during and after treatment. Studies looking at how well weight loss medication works combined the drugs with other changes. These included healthy eating, portion control, and plenty of regular exercise. It’s this combination that gets the best weight loss results.

Will I gain weight after stopping weight loss medication?

Once you stop taking weight loss medication, weight gain is likely. Studies have shown most people regained the weight they lost within a year of stopping injections. So, you’ll need to keep following a healthy diet and active lifestyle going forwards.

Weight loss medication isn’t for everyone. But, if you fit the criteria, evidence suggests you have a higher chance of losing weight than through lifestyle changes alone. Speak to a medical professional if you would like to find out more.

The Bupa weight management plan is designed for people with a BMI over 30 (or over 27 if you have a weight related condition). The plan is designed to empower you to achieve and maintain a healthy weight in a sustainable way.
Discover more about our medicated weight loss plan.

Niamh Hennessy
Niamh Hennessy
Lead Dietitian, Cromwell Hospital



Julia Ebbens, Health Content Editor at Bupa UK

    • NICE recommended weight loss drug to be made available in specialist NHS services. NICE., updated 8 March 2023
    • Wegovy made available in the UK for weight loss in people with type 2 diabetes and pre diabetes. Diabetes UK., Published April 2023
    • Ryan DH. Next Generation Antiobesity Medications: Setmelanotide, Semaglutide, Tirzepatide and Bimagrumab: What do They Mean for Clinical Practice? J Obes Metab Syndr. 2021;30(3):196-208. doi: 10.7570/jomes21033
    • Kwon J, Kwon G, Lee H et al. The Effect of Orlistat on Sterol Metabolism in Obese Patients. Front. Endocrinol. 2022; 13 .
    • Wegovy., accessed 15 September 2023
    • Ghusn W, De la Rosa A, Sacoto D, Cifuentes L, Campos A, Feris F, Hurtado MD, Acosta A. Weight Loss Outcomes Associated With Semaglutide Treatment for Patients With Overweight or Obesity. JAMA Netw Open. 2022;5(9):e2231982. doi: 10.1001/jamanetworkopen.2022.31982
    • Singh G, Krauthamer M, Bjalme-Evans M. Wegovy (semaglutide): a new weight loss drug for chronic weight management. J Investig Med. 2022;70(1):5-13. doi: 10.1136/jim-2021-001952
    • Di Folco U, Vallecorsa N, Nardone MR, Pantano AL, Tubili C. Effects of semaglutide on cardiovascular risk factors and eating behaviors in type 2 diabetes. Acta Diabetol. 2022;59(10):1287-1294. doi:10.1007/s00592-022-01936-6
    • Wilding JPH, Batterham RL, Davies M, Van Gaal LF, Kandler K, Konakli K, Lingvay I, McGowan BM, Oral TK, Rosenstock J, Wadden TA, Wharton S, Yokote K, Kushner RF; STEP 1 Study Group. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564. doi: 10.1111/dom.14725
    • Tak YJ, Lee SY. Long-Term Efficacy and Safety of Anti-Obesity Treatment: Where Do We Stand? Curr Obes Rep. 2021;10(1):14-30. doi: 10.1007/s13679-020-00422-w

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