If you and your family could live off the profits of one drug, which one would you choose? A recent straw poll in my local pub suggested Viagra would be a popular choice (annual global sales peaked at more than $2 billion in 2012). A retired colleague went for Humira, a treatment for inflammatory conditions such as rheumatoid arthritis ($21.2 billion). I opted for the diabetes/slimming drug Mounjaro.
I have never prescribed any of the new slimming injections just for weight loss, but I know plenty of people, both patients and friends, who are taking them, all under the direction of private clinics. And sales of Mounjaro (tirzepatide), now the preferred choice over Ozempic/Wegovy (semaglutide) for many, are forecast to reach $34 billion a year by 2029. The profits should easily keep my daughters in the style to which they have become accustomed.
And it’s not all about weight loss. Barely a month goes by without some new research suggesting extra benefits for this family of drugs. Yes, they help people to lose weight rapidly — both those who have type 2 diabetes and those who don’t — but there is growing evidence that they may protect against stroke, heart attack, some types of cancer and dementia. They may even have a role in helping people with addictions to alcohol, tobacco and opioid drugs.
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It’s early days and more research is needed to explore these extra benefits, but there is already an indication that it’s not just the impact on weight that might be reducing the risk of heart disease, dementia and obesity-related cancers including breast and bowel. Indeed, a study that has just been presented at the European Congress of Obesity found that the reduced risks of cancer far exceeded that expected from weight loss alone, with researchers proposing that a second, anti-inflammatory action may be responsible.
Sales of Mounjaro are likely to have a further boost here in the UK as, from next month, GPs like me in England will be able to prescribe it on the NHS. I say next month but, judging by preparations in my county (Gloucestershire), there is still no clear plan as to how this is going to be implemented across the whole of the country.
And even when we are given the green light, access is going to be strictly limited with a gradual roll-out over the next few years. Initially it looks like GPs will only be able to prescribe Mounjaro to very obese people with a BMI of 40 or more (37.5 for some higher risk ethnic groups) and at least four of the following: type 2 diabetes, high blood pressure, high cholesterol levels, obstructive sleep apnoea (severe snoring) or heart disease. Lower thresholds can apply for those patients referred to specialist weight-management clinics, but access is very limited.
Little wonder so many people turn to the private sector, where eligibility criteria are much lower: you have to be over 18 and have a BMI of 30 or more, reduced to 27 if you have an underlying weight-related problem such as high blood pressure. Costs vary but typically start at about £130 a month.
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While I welcome any advance that helps to tackle obesity and its myriad complications, I do have some reservations about using these drugs to treat weight loss (they are well-established treatments for type 2 diabetes), not least that they will be seen as a substitute for, rather than a supplement to, diet and lifestyle measures.
I also worry about what will happen to people’s weight when they stop taking them, and about the implications for the NHS. The drugs may save money in the long term, but at what cost to other services in the short term?
Finally, there are the side-effects. I have listed some of these below, but I have a particular concern about the impact of rapid drug-induced weight loss on muscle bulk and strength. A study following 140 volunteers on semaglutide showed that about 40 per cent of the weight loss seen was muscle rather than fat, with more recent studies suggesting that this muscle loss may be even more marked with tirzepatide. Muscle loss (sarcopenia) happens to some degree with all weight-loss programmes but appears more pronounced with the new slimming jabs.
Ensuring you are eating enough protein and practising resistance/weight training should help to mitigate this loss, but most of the people I know taking the drugs are not doing either. And it shows, at least to my eyes. The older you are the greater the significance, as we all lose muscle bulk and strength from early middle age on — as much as 10 per cent during our sixties alone. Be careful.
The side-effects
Research suggests that for most people taking these drugs to lose weight, tirzepatide (Mounjaro) is the most effective.
They all work by decreasing appetite/increasing satiety: you feel full sooner and for longer.
Tirzepatide side-effects appear much the same as with semaglutide (Ozempic/Wegovy) and are mainly gastrointestinal, the most common complaints (1 in 10 or more) being nausea, vomiting, diarrhoea and constipation.
In rare cases these drugs may trigger gallbladder problems (gallstones) and, more worryingly, inflammation of the pancreas (pancreatitis).