BeautifulPeople.com, which boasts 550,000 users worldwide and has a strict ban on 'ugly people', said it acted after vigilant members noticed 'fatties roaming the site'.
Most of those expelled came from the UK, US and Canada, and had somewhat foolishly uploaded photos revealing they had 'let themselves go' over Christmas and the New Year.
Skin deep: Lets members accept or veto new applicants based on their photo
Robert Hintze, the site's founder, said: 'We mourn the loss of any member. But our users demand the high standard of beauty be upheld.
'Letting fatties roam the site is a direct threat to our business.'
Almost 900 members from the UK were thrown out and told to re-apply once they had lost weight.
Managing director Greg Hodge said: 'We responded to complaints by moving the newly chubby members back to the rating stage. This is the same as having them re-apply.
'Their re-applications were reviewed by existing members and only a few hundred were voted back in. Over 5,000 were rejected.'
The social networking site allows its members to decide on who should be allowed to join.
Admission to the site is only allowed after accepted members vote on a photograph of the applicant and a brief profile.
No way: The website excluded people for being overweight and told them to re-apply after shedding some pounds
Members of the opposite sex vote 'Yes definitely', 'Hmm yes, O.K', 'Hmm no, not really' and 'NO Definitely NOT' to decide who is allowed into the site.
Mr Hodge said the 'festive fatties' have become an annual problem: 'Every year we see that some of our members from western cultures eat and drink to excess over the holidays and clearly their looks suffer.
'In the UK and Canada, Christmas and the New Year are all about over-eating, over-drinking and watching TV on the sofa.
'It's no wonder that so many members have been expell
ed from the network. We hope they will be back after shedding the festive pounds.'
In an attempt to soften the blow to those given the boot the website sent details of fitness centres where they can lose weight.
Mr Hodge said they had already received many new applications to join the site, with the majority of applicants from Brazil.