Appetite Suppressants

Appetite suppressants are medications or supplements that can aid weight loss. They work in several ways, including reducing hunger or cravings and acting on the areas of the brain that regulate appetite. They are often taken as part of a wider weight management programme that includes dietary changes and increased physical activity.

Some appetite suppressants can influence hormonal or communication pathways in the body to reduce your appetite. For example, some act on the brain’s hunger centre, also known as the hypothalamus, to release signals that create a feeling of fullness and reduce your cravings. Whereas other types of appetite suppressants can mimic specific digestive hormones like glucagon-like peptide-1 (GLP-1) to slow down digestion and signal to the brain to eat less.

Several types of appetite suppressants are available, including prescription and over-the-counter options.

Prescription appetite suppressants

Several prescription appetite suppressants are available in the UK. These medications can only be prescribed by registered healthcare professionals. This ensures they are safe and effective for you and your health needs.

1. Naltrexone with bupropion is a combined medication that targets the reward system and appetite control centre in the brain. It works by reducing food cravings, making you feel full, and helping you stop overeating. It is available under the brand name MySimba.
2. Semaglutide, available as Wegovy for weight loss, works by imitating the hormone GLP-1, which is released by the gut after eating. It slows down digestion, increases the feeling of fullness, and stops you from overeating.
3. Tirzepatide or Mounjaro is a dual-acting GLP-1 and GIP receptor agonist that is effective for both weight loss and blood sugar control. It works like Wegovy but may have a greater effect as it mimics 2 hormones instead of 1.
4. Liraglutide or Nevolat, is a GLP-1 receptor agonist that is similar to Wegovy (semaglutide) but requires daily rather than weekly injections. It manages appetite and is approved for weight loss in the UK for people who meet the eligibility criteria.

Non-prescription appetite suppressants

Non-prescription appetite suppressants are also widely available in the UK but should be approached with caution. Some examples include:

1. Caffeine-based supplements are sometimes marketed for their ability to temporarily suppress your appetite but they can also cause side effects like insomnia or jitteriness.
2. Green tea extract is often included in weight loss supplements because of its potential fat-burning and appetite-suppressing properties. However, results can vary between individuals and there is limited information about how it works for appetite.
3. Glucomannan is a type of water-soluble fibre that swells when it comes into contact with water in the stomach, creating a sense of fullness which may reduce your calorie intake. Other examples of dietary fibre that may be taken in a similar way include psyllium husk, apple pectin, and fenugreek. Water-soluble dietary fibre is usually included in non-prescription appetite suppressants like ‘XLS-medical appetite reducer’.

These products are usually sold as food supplements rather than over-the-counter medications. Unlike prescription medications, these products do not undergo the same rigorous testing and many do not have the scientific evidence to back up their claims. So, it’s important to speak to a doctor or health professional before using them for appetite control.

Appetite suppressants not available in the UK

Some appetite suppressants that are available abroad are not approved in the UK by the NHS because of safety concerns. For example, phentermine, sold under the brand name Adipex-P, and diethylpropion are not available in the UK from the NHS. Phentermine has not been researched in many long-term case studies, meaning it should only be used for a short time. It has also been shown to cause adverse effects in people with health conditions, especially heart disease, high blood pressure, or in those who are pregnant. Many countries have banned phentermine for weight loss because of this.

These appetite suppressants, however, are legal with a private prescription, such as from a slimming clinic. Yet, there are safer alternative options available, like semaglutide, tirzepatide, and liraglutide.

Appetite suppressants can work in several ways to reduce hunger and food cravings.

Gut hormone regulation

GLP-1 receptor agonists like Wegovy and liraglutide mimic the GLP-1 hormone, while Mounjaro mimics the actions of GLP-1 and GIP to:

• reduce appetite by signalling to the brain that you’ve eaten
• delay gastric emptying to increase feelings of fullness

Neurotransmitter modulation

Some prescription appetite suppressants, such as phentermine, work by acting on brain chemicals like dopamine and norepinephrine to suppress appetite.

Acting on reward pathways

Medications like MySimba act on the areas of the brain responsible for appetite regulation and reduce the brain’s reward response to food which can help you cut down your calorie intake.

Water absorption

Some over-the-counter appetite suppressants, like those that contain water-soluble dietary fibre, work by absorbing water in the stomach and expanding in size to make you feel full and lower your appetite.

In the UK, prescription-only appetite suppressants can be prescribed by a registered health professional to people who meet the following criteria:

• a BMI of 30 or more or
• a BMI of 27 or more and 1 or more weight-related health conditions such as high blood pressure (hypertension), type 2 diabetes, or sleep apnoea

As with all medications, there is a risk of side effects if you take prescription or over-the-counter appetite suppressants. However, not everyone will experience them.

The side effects differ from medication to medication. You should always read the possible side effects listed in the information sheet that is provided with your medication.

Prescription appetite suppressant side effects

The table below outlines some of the most common prescription appetite suppressant side effects.

Non-prescription appetite suppressant side effects

Non-prescription appetite suppressants can also cause side effects.

For example, glucomannan can cause:

• diarrhoea
• gas
• stomach pain
• bloating

Other possible side effects of over-the-counter appetite suppressants include:

• constipation
• feeling or being sick
• heartburn
• headaches
• fatigue
• sleep disturbances
• taste changes
• low mood

These depend on the substance that you take and this list is not exhaustive. It’s best to check the information that comes with the appetite suppressant and speak to your doctor.

The effectiveness of appetite suppressants varies depending on the individual and the medication used.

Prescription appetite suppressants

Prescription appetite suppressants like semaglutide and tirzepatide have shown significant weight loss results in clinical trials when taken at the maximum maintenance dose.

For example, Mounjaro can help people lose an average 22.5% of their starting body weight over 72 weeks on the 15mg dose.

Wegovy, on the other hand, can help you lose an average 15% of your initial body weight in 68 weeks on the 2.4mg dose.

Liraglutide is a daily self-injectable appetite suppressant that helps people lose on average 8% of their starting body weight after 56 weeks at the 3mg dose.

MySimba, a prescription-only weight loss pill that contains a combination of naltrexone and bupropion, has been shown to help people lose an average of 8.1% of their starting weight after 56 weeks of treatment.

However, these medications are not a standalone solution and they work best when combined with other lifestyle changes such as a calorie-controlled or healthy, balanced diet and increased physical activity.

Non-prescription appetite suppressants

There is little scientific evidence to support the claims that over-the-counter products act as appetite suppressants. For example, an 8-week study investigating the effects of glucomannan on weight loss found that although the supplements were well tolerated they didn’t significantly change the individual's body weight, promote weight loss, or alter hunger levels.

Research into the effects of green tea extract on weight loss are mixed. One review found that green tea can result in a small but not significant loss of weight in obese and overweight individuals. Another study found that a 12-week treatment with a high-dose green tea extract resulted in significant weight loss in women with central obesity.

In the UK, prescription appetite suppressants undergo stringent testing and regulatory processes to make sure they are safe and effective.

Medications like Wegovy, Mounjaro, and liraglutide have been approved by the Medicines and Healthcare products Regulatory Agency (MHRA) and are available with a prescription from a registered healthcare professional. MySimba is not available on the NHS and is only available with a private prescription.

However, if you are looking to request appetite suppressants or weight loss medications online, it is important to check that the source is regulated and reputable. It is illegal for weight loss medications to be sold in the UK without a prescription from a doctor or other registered healthcare professional.

Non-prescription suppressants are not subjected to the same strict regulatory processes. Therefore, you must purchase products from reputable manufacturers and speak to a doctor or pharmacist before trying any new medication.

While appetite suppressants can be a popular and tempting weight loss option, they are not the only available treatments.

Medical alternatives to appetite suppressants

Orlistat is a prescription-only medication that's also available under the brand name Xenical. It is a lipase inhibitor, which means it prevents an enzyme called lipase from absorbing around a third of the fat you eat, and this is instead passed out from your body in your stools. This can help you lose weight as you aren’t taking in as much fat from your diet.

Orlistat has been shown to help 37% of people lose at least 5% of their starting body weight after 12 weeks. An over-the-counter version of orlistat, alli, is available to buy without a prescription.

Weight loss or bariatric surgery is sometimes offered in the most severe cases. For example, it may be available on the NHS if you have a BMI of 40 or more or between 35 and 39.9 and you have a serious health condition that may improve with weight loss. Some surgery options include:

• gastric bypass
• sleeve gastrectomy
• gastric band
• gastric balloon

Lifestyle changes

Some of the lifestyle changes you can make to aid weight loss, include: