The survey, carried out by weight loss aid SlimWeight Patch, interviewed 948 people, found that adding just half a stone is enough for their partners to simply look elsewhere.
42 per cent of men interviewed said they would be attracted to their girlfriends a lot lesser should they put on extra weight.
And five per cent even said they would consider ending the relationship altogether, reports the Daily Mail .
Women, however, are not so shallow. More than three quarters of respondents said weight gain was a turn off and 21 per cent admitted they would find their partner more attractive.
“A lot of people will find these results hard to take and with Britain getting fatter as a nation it’s surprising that weight gain can have such an impact on a person’s perceived attractiveness,” said Dr Tim Thurlings, from SlimWeight Patch.
“When questioned how much weight gain was acceptable, we found that piling on a few pounds was OK, but anything over half a stone was viewed by many as a real turn-off,” he added.
He added that crash diets should be avoided as they may end up looking worse than before.
“It can be easy to put on weight, particularly for women, so if your partner is shallow enough to ditch you then maybe you shouldn’t be with them in the first place,” he added.