Common questions about weight loss medicines

Your healthcare provider will work with you to make a decision about the most suitable weight loss option for you. Your healthcare provider will consider other health conditions you may have and other medicines you are taking. You might also like to consider the following.

How does the medicine work?

Weight loss medicines work in different ways – they can affect appetite, digestion, or metabolism. Different types of medicines may suit different people's needs.

• Saxenda and Wegovy mimic a hormone (GLP-1) that's naturally released in your gastrointestinal tract in response to eating. These medicines suppress (control) your appetite by making you feel more full and less hungry. This can lead to eating fewer calories and losing weight.
• Contrave is a combination of 2 medicines – naltrexone and bupropion. These medicines work together in your brain to help reduce your body's signals that trigger the feeling of hunger. This means you can feel full with less food and have fewer food cravings when you're not hungry.
• Duromine is a stimulant medicine that works to suppress your appetite by directly affecting the area of your brain that controls your appetite making you feel less hungry. It's only recommended for short term use.
• Xenical works on an enzyme in your gut called pancreatic lipase, which reduces fat absorption in your gut by about 30%.

Efficacy – how well do the medicines work?

Weight loss medicines differ in how much weight loss they help people achieve. Your healthcare provider will monitor your weight loss monthly in the first 3 months and then on an ongoing basis to see if it's the right option for you and how long you will need to keep taking it.

Safety and side effects

Weight loss medicines, like all medicines, have side effects. Some side effects can be serious or even dangerous, especially for people with certain health conditions, such as heart disease, high blood pressure or psychiatric conditions. The risk of side effects may also depend on other medicines you're taking. If side effects are unpleasant people may stop taking the medication early or miss doses, reducing its effectiveness.

Is the medicine available as an injection or tablets?

Saxenda and Wegovy are given as an injection under the skin. Saxenda is given as daily injection, while Wegovy is given as weekly injection. Xenical, Duromine and Contrave are available as tablets or capsules.

Cost

Weight loss medicines are not subsidised in Aotearoa New Zealand, which means you'll have to pay for them yourself. They vary in price, costing between $100 to $500 per month. Most people are on these medicines long term, so the expense adds up quickly. Ask your healthcare provider how much they will cost before you start your course.

The effects of weight-loss medicines are not permanent. When they stop taking them, most people will regain weight over time. However, having healthy lifestyle habits may help limit weight gain.

Calorie-controlled eating

• It's important to adopt a healthy eating plan – a balanced and nutritious diet that meets your daily energy requirements.
• It's also important that you can stick to the diet long term, rather than a choosing a fad, or quick fix diet.

Regular exercise

• At least 2.5 hours of moderate intensity physical activity per week should be included in all weight loss plans.
• Exercise also leads to increased muscle mass and fitness, and improved heart health and mental health.
• Perform muscle strengthening activities 2 days of each week.
• Some physical activity is better than none – increasing physical activity of any kind is beneficial. Read more about how to increase your activity levels.

Different people respond differently to weight loss medicines and your healthcare provider can help you decide whether using weight-loss treatment long term is suitable for you.

• Once you've started treatment with a weight loss medicine, your healthcare provider will monitor you on a regular basis for side effects and your response to treatment.
• Usually people who lose weight after 12 to 16 weeks of treatment continue to lose weight at 1 year and beyond.
• For people who are overweight or obese, a lasting weight loss of 5 to 10% can have important health benefits such as lower blood pressure, blood glucose and triglyceride levels. If you're not managing to lose enough weight (eg, weight loss <5% after 3 to 4 months), the medicine should be stopped, as the long-term benefits are likely to be outweighed by the risks and costs.

Yes, there are medicines that shouldn't be used for weight loss. These include:

• Laxatives: Laxatives shouldn't be used for weight loss. Any weight lost by using laxatives is short term, due to fluid or water loss. This is harmful as it can lead to serious problems, such as dehydration and salt (electrolyte) disturbances, and in some cases dependence.
• Thyroid hormones: Thyroid hormones (eg, Eltroxin) are not appropriate for losing weight unless the weight gain was caused by an underactive thyroid (hypothyroidism). 
• The use of diuretics, chorionic gonadotrophin, or amphetamines is not appropriate for losing weight.

Evidence that weight loss medicines directly improve fertility is lacking. Being overweight or obese can reduce fertility in men and women.

• For women, being overweight or obese affects fertility by causing hormonal imbalances, problems with ovulation and period problems. It's also associated with PCOS, a common cause of low fertility or infertility.
• For men, fertility may be reduced by extra weight leading to hormonal imbalances, issues with sperm quality and erection problems.

Overall, even a small weight loss can improve fertility and pregnancy health. You have a greater chance of getting pregnant and having a healthy baby if you are close to a healthy weight. Weight loss in men who are overweight or obese can improve their total sperm count and quality.

Note: Weight loss medicines are generally not safe to take during pregnancy, so family planning should be discussed with your prescriber.