Five in 10 women only realise they need to lose weight when seeing themselves in an unflattering photograph, it has been revealed.

Experts asked 1000 women who have embarked on diets in the last five years the reasons behind their bid to shed a few kilos. And the results showed that many began slimming down when an old snap revealed lumps and bumps they didn't know they had before. Even passing a shop window or mirror can be the defining moment for many after being shocked at the face and body staring back at them.

Realising a favourite pair of jeans no longer fit and having to buy a bigger dress size when shopping also ranked highly on the list of reasons to lose weight.

"It is all too easy to become complacent with our body shape and size, and think we are doing okay, when really we’re carrying round a few extra pounds," a spokesman for EatWater.co.uk, which conducted the study, said.

"A photograph can be like a bolt from the blue – often people are absolutely flabbergasted that they could have let things get so bad."

Even old photographs can bring to light current weight issues – as 42 percent of girls have dieted after seeing how much weight they have put on since the pictures were taken. Preparing for a holiday abroad was a major trigger for weight loss too, as was feeling self-conscious when going swimming. A third of women over the last five years have slimmed down to attend someone else's wedding – while 17 percent have done the same for their own big day.

Other weight loss triggers include realising you are the fattest person in the office, a dwindling sex life, and being cheated on by a partner. The study also looked into the average weight loss experienced by women who find themselves in one of the above scenarios.

It shows that when seeing an unattractive pic, women go on to lose a staggering 14 pounds on average. Ladies will also lose 6.35 kilograms after being dumped – in a bid to get back on the dating scene. And women shed around five kilos in order to feel more confident in their holiday bikinis. Desperately wanting a new job, and wanting to fit into a favourite pair of jeans also lead to a respective weight loss of around five kilograms.

But just under half of women admit that they find it hard to maintain weight, and are more likely to diet for occasions than for any other reason. In fact, the average female goes on at least two diets a year, which last around three weeks each time.

TOP 20 WEIGHT LOSS TRIGGERS

  1. Being shocked at how fat you look in a photograph
  2. Catching a glimpse of yourself in a shop window or mirror
  3. Realising you couldn’t fit into a favourite pair of jeans
  4. Go shopping and realise you have to buy a bigger dress size
  5. Looking through old photographs you realise how much weight you have put on recently
  6. Preparing for a holiday abroad
  7. Feeling self-conscious when swimming
  8. Attending a wedding
  9. A good friend loses weight and looks amazing
  10. Before a special party
  11. Preparing for your own wedding
  12. You realise you are the fattest person in the office
  13. Someone asks if you are pregnant
  14. Your sex life has dwindled
  15. A partner loses weight and you’re the only fat one
  16. Getting back into the dating game after being dumped
  17. A partner cheats on you
  18. A sibling loses weight and you feel jealous
  19. Starting a new job
  20. You suspect a partner is having an affair