Peptides for weight loss: how they work

Peptides are chains of amino acids, which are the building blocks of proteins. They act as signaling molecules in the body, influencing processes like hormone regulation, immune response, and metabolism.

Your body naturally produces peptides involved in key functions like appetite control, digestion, and metabolism. For example, peptides such as glucagon-like peptide-1 (GLP-1) are naturally released after eating, helping regulate appetite and blood sugar levels.

Some medications contain synthetic peptides designed to mimic these natural peptides. Peptides are typically used in treatments for things like:

• weight loss
• type 2 diabetes
• HIV
• irritable bowel syndrome (IBS)

The peptides used in these medical treatments are prescription-only medicines, meaning they can only be obtained with a doctor’s approval.

Yes, peptide medications can help with weight loss. Specifically, GLP-1 receptor agonists like semaglutide have shown significant effectiveness in clinical trials. Studies have demonstrated that semaglutide can result in an average body weight reduction of 14 to 20% for people without type 2 diabetes. This makes peptides one of the most promising treatment options for those managing obesity.

Peptides can influence appetite and weight by acting on the gut–brain axis, a communication pathway that creates signals from the digestive system to help regulate hunger and feelings of fullness.

Peptides involved in appetite regulation

Naturally occurring peptides help regulate appetite through the gut–brain axis. Ghrelin, released by the stomach, stimulates hunger, while GLP‑1 and peptide tyrosine tyrosine (PYY), released after eating, promote fullness and help regulate blood sugar. These peptides are key signals that guide the body’s energy intake and fullness responses.

GLP-1 and related peptides

GLP‑1, in particular, is a highly studied peptide for weight loss, with numerous clinical trials demonstrating its effectiveness in reducing body weight and regulating appetite.

It is released by the intestines after eating, promoting fullness, slowing down the speed your stomach empties and improving insulin secretion. These effects help reduce appetite and support weight loss.

Semaglutide, a synthetic GLP-1 receptor agonist, mimics this natural peptide to support weight loss.

Certain peptides can help you lose weight, but their effectiveness can vary. The following are some of the most well-known peptides used for this purpose.

Tirzepatide (Mounjaro)

Mounjaro is a prescription weight loss medication composed of peptides that mimic natural gut hormones, GIP and GLP-1, helping with appetite control, feeling full sooner and blood sugar regulation.

Semaglutide (Wegovy)

Semaglutide is a synthetic GLP‑1 receptor agonist, a lab-engineered peptide that helps regulate appetite and blood sugar. When used as part of a structured weight management plan, semaglutide has been shown to produce significant weight loss.

Popular treatments that contain semaglutide include Wegovy, which is specifically approved for chronic weight management. Ozempic, another semaglutide treatment, is licensed only for type 2 diabetes in the UK and is not approved for weight loss.

Liraglutide (Nevolat)

Nevolat is a prescription medication used for weight loss. It contains liraglutide, a synthetic version of the body’s natural GLP-1 hormone. Nevolat works by targeting receptors in the brain that help control appetite, making you feel fuller and helping you eat less. It also helps regulate blood sugar levels.

Nevolat is most effective when combined with a reduced-calorie diet and increased physical activity. It’s typically prescribed to adults who are overweight or obese and meet specific body mass index (BMI) criteria. The treatment is continued only if significant weight loss is seen after an initial trial period.

Any medication that influences appetite regulation can cause side effects. The most common side effects of peptides like Wegovy and Mounjaro are gastrointestinal, including:

• nausea
• vomiting
• diarrhoea
• constipation
• abdominal pain
• bloating
• reduced appetite

These side effects occur because these peptides slow down digestion and influence signals between the gut and brain. Most are mild to moderate and often improve over time. It’s important to discuss any potential side effects with a doctor before starting treatment.

In the UK, peptides that are prescribed by a doctor and regulated by the Medicines and Healthcare products Regulatory Agency (MHRA) are legal.

However, many peptides sold online, such as Ipamorelin, are unlicensed, unregulated, and potentially unsafe, particularly when marketed for weight loss. Always speak with a doctor before using any peptide treatment.

The table below shows which peptides are licensed for weight loss in the UK. If a peptide is not licensed for weight loss, then you should not use it for this purpose.

If you’re interested in prescription-only peptides for weight loss, the first step is a medical assessment with a qualified doctor. During the consultation, the doctor will review your health, current medications, and weight loss goals to see if the treatment is suitable for you.

At Asda Online Doctor, we can prescribe peptides for weight loss in the UK. After a consultation with one of our doctors, they will decide if this medication is suitable for you. If so, your prescription will be issued and your medication delivered directly to your home in discreet packaging.

Are peptides the same as weight loss injections?

It depends on what you mean by ‘peptides’. There are several kinds of peptides, and they can do different things to your body. Certain kinds of peptides are found in weight loss injections like Mounjaro and Wegovy.

However, when people promote ‘peptides’ you can buy on social media, they are often referring to non-prescription products which contain other kinds of peptides. These may not be regulated or approved for weight loss, so you should not use them for this purpose.

Can peptides help with fat loss without dieting?

Yes, prescribed peptides such as Wegovy and Mounjaro can support weight loss, but they work best when combined with a healthy diet and regular exercise. Using them as part of a holistic weight management plan increases effectiveness and helps maintain long-term results.

Are peptide injections safe?

When prescribed by a doctor and used as instructed, prescription peptide injections such as Wegovy and Mounjaro are generally considered safe. Like all medications, they can cause side effects, so it’s important to monitor how you feel and speak to a doctor if you notice any adverse reactions.

Why are some peptides not approved for weight loss?

Not all peptides are licensed for weight loss because they must meet strict regulatory standards for safety and effectiveness. Many peptides sold online or promoted for weight loss do not have enough clinical evidence to show they are both safe and effective in humans. Others may have known safety concerns that prevent approval.

Do peptides affect metabolism or just appetite?

Peptides for weight loss can affect both appetite and metabolism. Drugs like GLP‑1 receptor agonists reduce hunger, increase feelings of fullness, and slow digestion, while also improving blood sugar control and how the body processes nutrients. This combination helps support weight loss beyond just appetite suppression.