DR MICHAEL MOSLEY: Why new weight-loss jab works better for women than men


A few years ago my wife Clare was startled when a patient came into her GP surgery and said lightly, ‘My husband is beating me.’

Fortunately, this was not a case of domestic violence: what the patient was really complaining about was that she and her husband had gone on the 5:2 diet at the same time and he was losing more weight than her.

Clare pointed out that although men do typically lose more weight when they go on a diet, women experience similar health benefits, certainly when it comes to key measures such as blood sugar control, even when they don’t lose as much weight.

But surprisingly, new research shows that women seem to do better than men when given new weight-loss drugs, such as semaglutide (brand names Wegovy or Ozempic). 

This is important given that earlier this week Rishi Sunak announced a £40 million pilot scheme to allow GPs to prescribe them.

DR MICHAEL MOSLEY: A few years ago my wife Clare was startled when a patient came into her GP surgery and said lightly, 'My husband is beating me

DR MICHAEL MOSLEY: A few years ago my wife Clare was startled when a patient came into her GP surgery and said lightly, ‘My husband is beating me

So why do men lose more weight when they go on a diet? It’s probably because we tend to be musclier and have a higher metabolic rate, which means we are burning more calories when sitting down and even when asleep.

Having higher levels of testosterone also helps: studies have shown that if you give men with low testosterone levels a hormonal boost, this leads to significant weight loss.

But curiously, recent research has shown that with the new weight-loss drugs, the situation is reversed, with women losing a higher percentage of body weight than men.

Drugs such as semaglutide work by mimicking the action of the GLP-1 hormone, which is released in your gut in response to eating. It prompts your body to produce more insulin, which reduces blood sugar levels. This is why it was originally developed for people with type 2 diabetes.

But these drugs also act on your brain, suppressing appetite. People who’ve tried them say one of the biggest changes is the drugs stop cravings. The result is impressive weight loss, though once you stop taking the drug there is often significant weight regain.

One of the first big studies that looked at semaglutide found that the men and women given the drug had, over 66 weeks, lost an impressive 2st 6lb (15.3 kg).

But less positive was a follow up study, published this April in the journal Diabetes, Obesity and Metabolism, which found they had regained two-thirds of that weight within a year of stopping the drug — whether this means people should be on the drugs for ever is clearly going to be an issue.

What was also striking was that the women in the trial lost a higher percentage of their initial weight than the men, around 18 per cent versus 13 per cent, according to a re-analysis of the data by Dr Alyssa Susanto, a researcher in the Faculty of Medicine and Health at the University of Sydney.

Dr Susanto, who presented her findings at the recent International Congress on Obesity, in Melbourne, didn’t speculate why this might be. However, I suspect it might be because these new drugs work so powerfully on the brain, reducing cravings — and research suggests women are more susceptible to cravings than men.

For example, a study from 2005, called Eating and Dieting Differences in Men and Women (published in the Journal of Men’s Health & Gender), concluded that men tend to overeat because they are ‘pleasure orientated’ (whereas craving something is more intense and dominates your thoughts).

Men also tend to go on diets for health reasons, often prompted by a doctor or partner. Women, meanwhile, are more likely to struggle with cravings for calorie-rich tempting treats.

Dr Susanto suggested studying male-female differences to weight loss could lead to better, more personalised treatments.

Although these gender differences are interesting, what this research really points to is the importance of first identifying and dealing with the reasons why you overeat.

This is what researchers from the Mayo clinic in the U.S. have been looking at: they’ve identified four different types of over-eater, based on different tests including how many calories people ate at a buffet meal and how long it took for their guts to empty.

The four types are:

  • Hungry brains: these people need to eat more than average to feel full, because the hunger centre in their brain remains ‘switched on’ for longer than average.
  • Hungry guts: this describes those who are hungry soon after eating and feel the need for frequent snacks. This seems to be because food goes through their stomachs faster than average.
  • Emotional eaters: as the name implies, they eat when stressed.
  • Slow burners: they have a slower metabolic rate than average.

In a recent clinical trial with 165 overweight volunteers, the Mayo researchers matched the different over-eater type with a particular weight-loss approach.

Those with ‘hungry brains’ were put on a time-restricted diet, full of fibre to fill them up. The thinking was that encouraging people to eat their food within a constrained time period would ‘switch off’ their brain hunger centre. 

Those with ‘hungry guts’ were given protein supplements to take with their meals, to keep them fuller for longer. Here, the thinking was that consuming more protein would delay their stomachs emptying and lead to earlier release of gut hormones that tell you when you are full.

DR MICHAEL MOSLEY: Those with 'hungry brains' were put on a time-restricted diet, full of fibre to fill them up. The thinking was that encouraging people to eat their food within a constrained time period would 'switch off' their brain hunger centre (file image)

DR MICHAEL MOSLEY: Those with ‘hungry brains’ were put on a time-restricted diet, full of fibre to fill them up. The thinking was that encouraging people to eat their food within a constrained time period would ‘switch off’ their brain hunger centre (file image)

The emotional eaters were given emotional support and asked to practise mindfulness, while the slow burners took protein supplements, like the hungry guts group, but also did a HIIT (high intensity interval training) programme, as this has been shown to be helpful at speeding up metabolism.

The results were interesting. Compared with a control group, put on a standard low-calorie programme, those who followed a tailor-made diet lost more than twice as much weight over 12 weeks.

They also lost more inches around the waist, experienced a greater improvement in mood and a greater drop in blood fat levels.

Larger and longer-lasting studies are needed, but what this research shows is that when it comes to weight loss, one size does not fit all.

Hidden risk in water

At this time of year I like nothing better than an evening swim in the nearby Thames. So far I haven’t done that, mainly because of stories about raw sewage being pumped into our rivers. 

But there’s another, more insidious threat, so-called ‘forever chemicals’ or PFAS (per-and polyfluoroalkyl substances), which have been used for decades to make food containers and non-stick cookware. 

Unfortunately, once they get into the environment they hang around for a very long time, which is bad news as some PFAS, even at low levels, can lead to problems such as infertility and cancer.

In the UK, the official limit for PFAS in tap water is 100 nanograms (ng) per litre, but in the U.S. it’s just 25ng for some PFAS. Meanwhile the European Union is planning to ban almost all PFAS within ten years.

In the meantime, filter your water and avoid microwaving food in the plastic containers from your take-away. I’ll also probably swim only in the sea.

Don’t be fooled by ‘junior doctor’ title   

My son Jack is returning to the UK next week after a couple of years working as a junior doctor in Melbourne, where he went to broaden his medical horizons and recharge his batteries after a long stint on a Covid ward.

Despite the name, most ‘junior doctors’ are highly trained professionals. It can take ten years or more to become an NHS consultant, which means you go on being classified as a junior doctor after medical school until well into your 30s, or even 40s.

DR MICHAEL MOSLEY: My son Jack is returning to the UK next week after a couple of years working as a junior doctor in Melbourne, where he went to broaden his medical horizons and recharge his batteries after a long stint on a Covid ward

DR MICHAEL MOSLEY: My son Jack is returning to the UK next week after a couple of years working as a junior doctor in Melbourne, where he went to broaden his medical horizons and recharge his batteries after a long stint on a Covid ward

So I wasn’t surprised to learn that ‘one of the most discussed motions’ at the recent Junior Doctors Conference was the term ‘junior doctor’, says the BMJ — it’s ‘misleading for the public … and undersells the incredibly valuable work that doctors of all grades do’.

While they’re looking for a more appropriate name, their strike action continues.

I have huge sympathy for patients whose lives are disrupted by these strikes, but my heart is also with the junior doctors who have over the past decade seen a big pay cut in real terms.

If this isn’t resolved, the risk is we see a flight of junior doctors to places such as Australia, where they have better pay and working conditions.

We desperately need to train more doctors, but also to cherish those we have.

I only hope the lure of friends and family is enough to keep Jack, and others, from booking a flight to work where they’re more appreciated.



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