Lesbian and bisexual women are more likely to be overweight than heterosexual women, research has shown for the first time, as experts said sexual identity should now be viewed as a health risk factor.

Researchers at the University of East Anglia studied 12 British national health surveys involving more than 93,000 people which recorded body mass index (BMI) and sexuality and found a striking link between weight and sexual orientation.

For women, being gay increased the odds of them being overweight by 41 per cent, an increased overall risk of 14 per cent. It means that you would expect an extra eight gay women of an unhealthy size in every 100 compared to heterosexual women (65% compared with 57%).

Bisexual women were 24 per cent more likely to be overweight or obese, however for men the opposite was the case, with gay men at three times the risk of being underweight.

“This is worrying because being overweight and obese are known risk factors for a number of conditions including coronary heart disease, stroke, cancer and early death,” said lead researcher Dr Joanna Semlyen, from the University of East Anglia's Norwich Medical School.

“Conversely, gay and bisexual men are more likely than heterosexual men to be underweight, and there is growing evidence that being underweight is linked to a range of health problems too, including excess deaths.