Peptides for Weight Loss

Peptides are a short chain of amino acids (usually 2 to 50), which are the ‘building blocks’ of protein.

Peptides link amino acids together through peptide bonds. When many amino acids are linked together, they form a polypeptide (between 10 and 100). Polypeptides then fold together in a certain way to make protein.

Peptides are found naturally in the body or in certain foods, medications, supplements and even skincare products. Peptide medications are prescription-only and can treat lots of different health issues, including:

• weight loss (in people who are overweight with a weight-related medical condition, or people who are obese) – GLP-1 agonists like Saxenda, Wegovy and Mounjaro
• type 2 diabetes – GLP-1 agonists like Mounjaro, Ozempic and Victoza
• HIV – such as peptide T-20 used in the medication enfuvirtide (Fuzeon)
• irritable bowel syndrome (IBS) – such as the Guanylate Cyclase-C receptor agonist (GCCA) medication called linaclotide (Constella)

Yes, prescription peptide medications do work for weight loss. Weight loss treatments containing peptides were first used in type 2 diabetes to control and manage blood sugar levels but were also found to help with weight loss due to their appetite-stimulating properties.

The active ingredients liraglutide (Saxenda), semaglutide (Wegovy) and tirzepatide (Mounjaro) are glucagon-like peptide-1 receptor agonists. They mimic the peptide hormone GLP-1, which is made up of 30 amino acids. Mounjaro also mimics another peptide hormone called glucose-dependent insulinotropic polypeptide (GIP), which is made of 42 amino acids.

These all work in the same way – by mimicking the effects of GLP-1 and in the case of Mounjaro, also GIP. When you take the injection, the medication binds to the same receptors and activates them in your body, essentially tricking your body.

Please note: ‘Peptides’ can refer to a wide range of products, some of which may include herbal or over-the-counter products. Only prescription peptide medications are proven to work and they can only be bought safely from regulated online services like ZAVA. Buying peptide products elsewhere online may be a waste of money and could potentially be dangerous.

How do peptide medications work?

Peptide medications work by simulating or mimicking a peptide and triggering the receptor. By having a similar structure. man-made peptides can still bind to receptors in your body and trigger their effects.

How do peptides work for weight loss?

In the case of weight loss, GLP-1 and GIP can:

• slow down gastric emptying (how quickly food empties from your stomach), making you feel full between meals
• reduce your appetite by sending signals to your brain that you’ve had food and are full

These effects, when taken alongside a reduced-calorie, balanced diet and more exercise, can help you lose weight.

As you feel fuller you’re less likely to snack between meals or get cravings, and because you’ve got a reduced appetite, you can safely and more easily reduce your calories for effective weight loss. It’s been proven in studies that people can lose up to 22.5% of their weight when taking Mounjaro (tirzepatide) at the highest maintenance dose of 15mg for 72 weeks.

How do peptides work for type 2 diabetes?

GLP-1 and GIP also trigger your pancreas to release more insulin. This helps people with type 2 diabetes to manage their blood sugar, but usually in lower doses than for weight loss. As a side effect of taking them for diabetes, you may lose weight but these aren’t made specifically for weight loss so won’t have the same results.

For other peptide medications and how they work, this depends on the condition being treated.

The best peptides for weight loss are:

Mounjaro

Mounjaro is a prescription-only medication that contains the active ingredient tirzepatide and mimics 2 peptide hormones (GLP-1 and GIP). It’s taken once weekly and works best when you take it at the same time and day every week, so the medication level stays steady in your bloodstream.

It follows a dosage schedule, increasing up to a maximum weekly maintenance dose of 15 mg but you can also stay on a lower dose. Mounjaro is manufactured by Eli Lilly.

Wegovy

Wegovy is also prescription-only and contains the active ingredient semaglutide which mimics the GLP-1 peptide hormone. It’s taken as a self-injection once a week and for best results should be taken at the same time and day each week.

It also follows a dosage schedule like Mounjaro, increasing to a maximum maintenance dose of 2.4mg although you can stay on a lower dose. Wegovy is manufactured by Novo Nordisk.

Saxenda

Saxenda is a prescription-only weight loss treatment that is currently long-term out of stock, partly due to the popularity of weekly weight loss injections. Saxenda contains liraglutide and is injected once per day, so has to be taken much more frequently than Wegovy or Mounjaro.

Saxenda isn’t available in the UK at the moment, but there should be a generic liraglutide injection available at some point this year.

How much weight can you lose on peptides?

The Wegovy study found that people lose on average 15% of their body weight after taking the 2.4 mg highest maintenance dose after 68 weeks. Lower doses were not studied at the time.

The Mounjaro study found that people lose an average of 22.5% of their body weight after taking the maximum maintenance dose of 15 mg after 72 weeks. Other doses included in the study were 5 mg and 10 mg.

Other results from the same studies include:

Saxenda shows less promising results even though it’s taken more often. Studies found that Saxenda can help people lose an average of 8% of their body weight after 56 weeks on a daily maintenance dose of 3 mg.

ZAVA can prescribe peptide weight loss treatment, including Wegovy and Mounjaro. We can prescribe Saxenda too, if it becomes available again. You can also get peptides prescribed by the NHS, but you’ll usually need to be referred to a specialist weight management service and the criteria for NHS prescription may differ from private services.

To get peptides for weight loss through our online doctor service, start by completing a brief consultation questionnaire. This includes taking a few pictures so our doctors can check that the medication is suitable without needing a face-to-face consultation.

If you meet the criteria and have no health conditions that could make treatment unsafe, our doctors will prescribe your chosen medication. It’ll then be sent to your home in discreet packaging.

If peptide medications aren’t suitable, we also prescribe weight loss tablets, such as orlistat, Xenical, alli and Mysimba.

Each peptide medication has its own risk of side effects and it’s always best to discuss this with your doctor first. You can also check your patient information leaflet. GLP-1-type peptides for weight loss, like Wegovy and Mounjaro, often cause gastrointestinal side effects.

Very common Mounjaro and Wegovy side effects

Wegovy:

• headache
• nausea
• vomiting
• constipation
• diarrhoea
• stomach pain
• weakness or tiredness

Mounjaro:

• low blood sugar when taken for management of blood sugar
• nausea
• vomiting
• diarrhoea
• constipation

Common Mounjaro and Wegovy side effects

Wegovy:

• dizziness
• low blood sugar when taken for management of blood sugar
• inflamed stomach (gastritis)
• gallstones
• hair loss
• injection site reactions
• indigestion
• burping
• gas

Mounjaro:

• gas
• fast pulse
• fatigue
• allergic reaction
• low blood pressure
• stomach pain
• bloating
• reflux
• hair loss
• injection site reactions
• dizziness

Uncommon Mounjaro and Wegovy side effects

Wegovy:

• fast heartbeat
• increased bilirubin levels (which can cause jaundice)
• a delayed emptying of the stomach
• an increase in pancreatic enzymes
• low blood sugar in people without diabetes

Mounjaro:

• gallbladder infection
• injection site pain
• increased calcitonin levels
• gallstones
• low blood sugar when taken with other diabetic medications

Rare or serious side effects you should be aware of before taking peptide medications

Wegovy may cause:

• Common: diabetic retinopathy complications – tell your doctors straight away if you notice changes in your vision
• Uncommon: kidney or bladder stones – speak with your doctor or go to A&E if you have back or lower stomach pain, a change in the colour of your urine and difficulty urinating
• Rare: hip fractures – call an ambulance if you think you’ve fractured your hip and can’t move
• Not known: bowel obstruction

Wegovy and Mounjaro can both cause:

• Uncommon: inflamed pancreas – see a doctor straight away if you have unexplained and long-lasting pain in your stomach and/or lower back
• Rare: a severe allergic reaction – this is a medical emergency and you or someone you’re with should call 999 straight away if you can’t breathe properly, have facial swelling and/or difficulty swallowing
• Not known: gastroparesis (severe delayed gastric emptying) – this is serious and you should see a doctor straight away if you have nausea, vomiting, bloating, stomach pain and you’ve not been able to pass stool

This may not be a complete list of side effects. For the most up-to-date information, please read the Wegovy patient information leaflet or Mounjaro patient information leaflet.

Are peptides safe?

Yes, despite the risk of side effects, peptide medications are safe for weight loss and other conditions when prescribed by a doctor. All medications can cause side effects but your doctor will monitor your progress and you should speak to them straight away if any side effects become severe, or don’t go away after several days.

Peptide medications aren’t safe for everyone, which is why they require a prescription. You won’t be able to take them if you don’t meet the prescribing criteria or you have an allergy to any ingredients in the medication.

Peptide medications for weight loss may be right for you if you:

• struggle to lose weight through diet and exercise alone
• meet the criteria to use peptides safely
• are comfortable self-injecting

You must also be ready to stick to a reduced-calorie diet and exercise plan, as peptide medications for weight loss won’t work without lifestyle changes.

You’ll need to meet the requirements for our doctors to prescribe peptides for weight loss, which are:

• a body mass index (BMI) of 30 or above (obese)
• a BMI of 27 to 30 with one or more weight-related medical conditions, including high blood pressure or prediabetes

You can use our BMI calculator to check your BMI before requesting a prescription and you’ll need up-to-date weight and height measurements.