Coming back from holiday humming "Everybody's beautiful... / In their own way", however, tends not to last long - for women in particular. While men are often either unaware of their sagging parts, or simply don't care about them, women dwell morbidly on their own imperfections.
Dr Judith Rodin, an American expert on weight and behaviour, writes in her book Body Traps that "even as children, females are more dissatisfied with their bodies than are males". She explains that few people have an accurate mental picture of how they really look, because almost everyone's perceptions are distorted by comparing themselves with others. "We all have problems knowing our bodies because our mirror image is not the total story. Our body concept is made up of much more than our reflection." One American study showed that 95 per cent of women overestimate the size of their own bodies - often by as much as 50 per cent.
Such overestimating is easy to do. "I always thought I was quite realistic about how I looked, and always imagined myself as quite big, not fat exactly, but substantial," says Louise Ward, a marketing assistant. "But one day I was out at a restaurant where the walls were all mirrored, and I caught sight of this woman. I thought: `Oh, she's wearing the same blouse as me, but she's really slim.' Then I realised it was my own reflection. It was a real boost, seeing myself just for an instant as a stranger would see me." Louise is a size 12 - which translates as somewhere between small and medium.
"I've been on a diet on and off since I was about 16," says Lucy Stewart- Brooks, a language teacher aged 28. "I was a fat teenager, the fat girl of the class, and even though I'm a size 12 now and logically I know that's about right for me, I am just obsessed with being a size 10. I'm perfectly intelligent, I know that happiness is not measured in dress sizes, that they are a completely arbitrary measure, but I just don't feel slim until I hit the magic number. When I'm size 10 I feel great, confident, slender, but when I'm size 12 I just feel like a blob."
Men are not immune. Television host Dale Winton, who has lost five stone, says: "When people say I look nice I still find it difficult to believe". Interviewed last month, he confessed: "Now, when I'm thinner, I always think I'm too fat. I was a fat child. My mother was always sending me to health farms, so I've always had a distorted body image."
"At school I was a really skinny, puny little kid, the one who'd get sand kicked in his face on the beach. I've filled out a lot since then, but I always vaguely think of myself as a weed," admits a perfectly strapping young man.
It can be difficult to change your perceptions, even when you know they are wrong. "I've just spent a whole year losing nearly four stone," says one young woman wistfully, "but somehow I'm still wearing all my old clothes, even though they're hanging off me. It's because I just can't bring myself to buy anything close-fitting in a small size, it somehow feels all wrong to be thinking about showing off my figure instead of hiding it."
The overwhelmingly negative way in which being fat is perceived means that even slightly overweight people often have a poor body image. Reprogramming people not only to be realistic about their size, but to accept it, is the latest weapon in the fight against obesity. Traditionally, the treatment of obesity has relied on medical intervention: appetite-suppressants, stomach stapling, waist cords that dig in when the patient eats too much. New Scientist magazine reported last month that doctors and psychiatrists are starting to turn to body-image workshops and self-esteem therapy to give patients a positive outlook on losing weight, even if they have to come to terms with the fact that they are never going to look like Kate Moss.
Even if it's difficult accurately to gauge your own size, why do women consistently see themselves as larger than life rather than slimmer than they really are? Dr Jane Wardle, a clinical psychologist at the Institute of Psychiatry, has conducted a number of research projects investigating body perception. " Most women are much more exposed to naked perfect bodies than imperfect ones. Most of us don't see our friends in the nude - what we see are film stars like Demi Moore or Debra Winger. Or, rather, what we see are their body doubles, who are even more perfect, and we make our comparisons with this kind of body." Men, she says, are as vulnerable as women in some ways. "There is a certain part of their bodies that they are very hung up on indeed."
Dr Wardle is not sure that all inaccurate perceptions are wholly subconscious. "In one experiment, women were asked to assess their body size. They were then told that they hadn't been very accurate, and asked to re-do the test. They all shifted their estimates downwards, so at some level they must have been aware of their exaggerated perception.
"My view is that women over-estimate partly because they would be ashamed to be seen under-estimating. They don't want to risk anyone saying or thinking: `Oh, she's not as slim as she thinks she is'. And it's a way of eliciting reassurance - having people say `Oh, of course you're not fat!' It's like someone who is worried about having a big nose and keeps drawing attention to it, so that everyone will keep saying that it's not that big."
Dr Wardle's research has shown that pregnancy is one way of calming body image anxieties - for nine months, at least. "When you're pregnant you gain a different perspective on your appearance. Your main priority is having the baby. Many women have said it's a break from the pressure, a holiday from trying to look slim. And when people go on holiday, they find it's enormously good. On the beach or wherever they see all shapes and sizes, and after a while, they don't even think about it any more."
Not thinking about body imperfections on the beach, however, is one thing; not thinking about them at all is impossible for many people. Obesity levels have never been higher - one in two Britons is overweight, one in seven dangerously so - but at the same time, an estimated 2 to 3 per cent of women suffer from an eating disorder such as anorexia or bulimia. Ten per cent of children are overweight, and nutritionists expect this number to double by the end of the decade due to poor diets; but a recent study revealed that more than a quarter of Britain's five-to-seven-year- olds wanted to be thinner. One in six children is already attempting to diet, and eating disorder clinics such as Rhodes Farm in north London are admitting anorexic six-year-olds.
So whatever happened to the happy medium? Or even being medium-sized? According to social psychologist Dr Halla Beloff, not everyone is desperate to be model-thin. "It's true that the average measurements are going up, and so is the number of overweight people. But quite a lot of those say: `So what if I weigh more than I did before?' There are lots of people who are perfectly happy to be a size 14," she says firmly. And anyway, she adds, such petty concerns tend to fade with maturity. "Your perceptions change throughout life. When you are young, you might think you're too short, the wrong size, or whatever. As you get older, and everything else in your life starts to fall into place, you wonder what you were worried about."
WHAT THEY THINK
NICK, 30, sales manager
"I'm too puny. It's my shoulders, really - they should be much squarer and broader. As it is, clothes just don't hang well on me. My knees are bony and stick out, and I've been unhappy with my legs since a girl at school told me they looked like matchsticks. My wrists are similar - far too thin. It's impossible to buy a watch strap that fits.
"I'm also convinced that my nipples are smaller than other men's and they're too far apart. I'm worried I'll develop a hairy back - I've already got a few shoulder sprouters, which I keep a very sharp eye on.
"I'm more aware of my body in front of women than men - with girls I make an effort to hold my shoulders back. I'm far less self-conscious now than I was 10 years ago, though."
SOPHIE, 32, actress
"The things I like about myself are also the aspects I worry about: my legs are too skinny compared to the rest of my body; my bosoms are too big; and I'm too chunky in the middle. I sometimes compare my figure to other people's but I'm never that worried. Saying that, I look like a white blob compared to the other three in the photograph.
"My sister describes me as a potato with cocktail sticks at the bottom and a pea on the top. The description doesn't really upset me - I think it's quite true.
"As a teenager I used to feel a lot more self-conscious about my body; now I'm used to it. These days, how I feel about my body depends on what's going on in my life: my mood, the time of month and the state of my love life."
MATTHEW, 30, travel director
"I feel overweight - by about half a stone. My legs are too short and the top bits of my thighs are far too big. I'm always aware that the veins on my legs stick out.
"I also worry that I've got a big bum and a thick neck. I think my hands are coarse-looking and plump - I'd like them to be more elegant. My feet aren't much better - they look deformed from wearing poor-fitting shoes when I was young. I'm always embarrassed about an appendix scar on the right of my stomach - highly unattractive.
"I'm more aware of my body as I get older. It takes far more effort to stay fit and slim. I suppose I feel good about my shoulders; they're quite broad. But, all in all, I do wish I had an athlete's body."
JO, 30, TV producer
"People tell me that my legs are nice but I've always wanted them to be longer. I've got a big bottom and I'm never sure about my bosoms. When I'm pre-menstrual they can get too big - I want bee-stings and hate the look of these big things sticking out in front. Sometimes I feel wimpy- looking - I'd like to have muscular arms, broader shoulders and a thinner waist. I fantasise about being one of those 5ft 8in, powerful Amazonian types. As it is, I feel too short.
"A few years ago an ex-boyfriend told me I had a `chicken neck'. I'm still paranoid that it looks scrawny.
"My self-image shifts with my psychological state. In general, I'd say I'm pleasantly surprised when people pay me compliments."Reuse content