6 days ago
Weight-loss injections could make you fitter without exercise
Weight-loss jabs could help people become fitter by making their muscles work more efficiently, evidence suggests.
Anecdotally, there is concern among people who use treatments such as Mounjaro that weight loss will make them less muscular, toned and strong.
However, a study analysing the body composition of more than 200 people with type 2 diabetes, found they lost no more muscle after a weight-loss jab than if they had lost weight by other means.
Meanwhile, they shed significantly more fat from within their muscles than they would have done losing weight another way.
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The loss of fat from the muscles after taking tirzepatide, the prescription injection sold as Mounjaro, could also boost someone's capacity to do physical activity.
That is because 'ectopic' fat found within the body, which gets into muscles and wraps in and around other organs, has been linked with poorer muscle strength and physical performance in both men and women.
Naveed Sattar, the lead author of the study and a professor of metabolic medicine at the Institute of Cardiovascular and Medical Sciences at the University of Glasgow, said: 'For the majority of people using the weight-loss injection tirzepatide, they experience an increase in their capacity for activity, meaning they can often walk for longer or be more active than before.
'Having less muscle fat usually means the remaining fat muscle cells are more efficient in generating power, which could explain the boost to people's exercise abilities. These results are hugely encouraging as less muscle fat is also linked to a reduced risk of cardiovascular disease and type 2 diabetes in many studies.
'However, we don't yet know how weight-loss injections remove additional muscle fat, and more evidence is needed to understand the mechanisms involved.'
Fat streaks within the muscles tend to increase when someone is more overweight or sedentary. They can be reduced through aerobic exercise such as jogging, walking and cycling. But the use of weight-loss injections to achieve a similar result could be useful for people who are unable to be as active because of their excess weight.
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The research, published in the journal The Lancet Diabetes & Endocrinology, looked at 246 people given varying doses of tirzepatide, or insulin in a previous study.
An MRI scan was used to quantify the amount of muscle and fat each person had in their thighs before the treatment, and a year after starting it. The amount of muscle lost by people using tirzepatide was compared to typical muscle loss in people of the same age and sex, losing the same amount of weight. Muscle loss was broadly similar for both groups.
However, the percentage of fat lost from their muscles was 0.5 per cent higher if they took tirzepatide than would be expected from losing the same amount of weight without the drug.
Researchers worked this out using data for almost 3,000 people taken from the long-running UK Biobank health study.
It may be that tirzepatide not only makes people feel fuller for longer and less hungry, but also removes ectopic fat from different parts of the body better than conventional weight loss. That could help to explain evidence suggesting weight-loss injections may reduce the risk of diabetes and many other chronic diseases.
