Private weight loss injections clinic in London, same-day endocrinology.

How they work

They mimic gut hormones released after eating. They slow stomach emptying, act on appetite centres in the brain, and for most people substantially reduce hunger and the constant background preoccupation with food that many describe as 'food noise'. They are given as a weekly injection, with the dose increased in steps over several months.

Those are averages. Some people lose considerably more, and around one in ten loses very little — which is worth knowing before starting, and a reason to review at three to four months rather than continuing indefinitely without benefit.

Side effects

• Nausea, vomiting, constipation, diarrhoea, reflux and burping are common, usually worst after each dose increase, and usually settle.
• Eat smaller portions, stop when full rather than when the plate is empty, avoid fatty and heavy meals, and keep fluids up.
• Gallstones are more common, partly because rapid weight loss itself causes them.
• Pancreatitis is uncommon but serious.
• Injection site reactions, fatigue and hair thinning during rapid loss.
• They interact with other diabetes medication and can affect absorption of other tablets.

When you stop

This is not a course of treatment with an endpoint. Trials consistently show that most of the weight returns over the following one to two years after stopping, along with the improvements in blood pressure and blood glucose. The medication treats the condition while it is being taken, in the way blood pressure tablets do.

That has practical implications worth thinking through before you start: the likely long-term cost, whether you will be able to continue, and what your plan is if you stop. Using the period on treatment to build eating patterns, activity and strength that can persist afterwards gives the best chance of holding some of the benefit.

Who should not take them

• anyone pregnant, planning pregnancy or breastfeeding — and note these medications can reduce the effectiveness of oral contraception, so additional contraception is needed
• a personal or family history of medullary thyroid cancer or MEN2
• previous pancreatitis
• severe gastrointestinal disease or gastroparesis
• anyone with a current or past eating disorder, without specialist input
• people seeking cosmetic weight loss at a healthy weight