A top professor has warned that not being able to wear the same clothes you did aged 21 could highlight that you're at risk of developing diabetes.
Prof Roy Taylor from Newcastle University spoke at the European Association for the Study of Diabetes' annual meeting - and previewed new research he has been working on.
In his talk, Prof Taylor emphasised how even people who were not overweight were developing the condition in greater numbers - but that it can be reversible.
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He said: "As a rule of thumb, your waist size should be the same now as when you were 21.
"If you can’t get into the same size trousers now, you are carrying too much fat and therefore at risk of developing type 2 diabetes, even if you aren’t overweight."
Prof Taylor has been running the ReTUNE study with colleagues including Dr Ahmad Al-Mrabeh, and though results of this are at an early stage, he said it had shown the benefit of losing "10-15%" of someone's body weight, even if you're not overweight, when it comes to reversing diabetes.
The trial - set to be completed early next year - is looking at the impact of fat around internal organs on the condition.
So far, those on the trial - all of "normal" weight - have been put on a restricted diet of 800 calories a day based on soups, shakes and non-starchy vegetables.
This has been done under medical supervision and such a diet is not recommended otherwise.
In the trial, the diet has lasted two weeks, before those taking part have been carefully supported to return to healthier long-term eating habits.
Participants have done this process three times - and of 12 taking part, eight have seen their diabetes go into remission and levels of fat around organs such as the liver and pancreas reduced.
Though to be treated with caution, this suggests that diet can be an early treatment for those diagnosed with diabetes who are not overweight.
Previously, as it was thought something different may cause diabetes in these people, doctors have been quicker to move to treatments like giving insulin.
Professor Taylor added: "These results, while preliminary, demonstrate very clearly that diabetes is not caused by obesity but by being too heavy for your own body. It's due to having too much fat in your liver and pancreas, whatever your BMI."
Dr Lucy Chambers, from Diabetes UK, welcomed the news.
She said: "We welcome these early results from the ReTUNE study and eagerly look forward to the full results expected next year, which will advance our understanding of how internal body fat contributes to type 2 diabetes."
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