Fretting about your long-term health prospects? Worried about whether you are going to succumb to heart disease and cancer? According to new advice from scientists, the answers to your questions could be as close as your nearest full-length mirror. Take a long, hard look at your body shape, they say, because it could reveal a whole host of clues about your longevity and your risk of serious illness.
Here's why: for more than a century, doctors have been aware that there is a correlation between certain body shapes and an individual's health prospects. Much of what they have discovered isn't fully understood: but the evidence is clearer than ever that the data they have collected isn't just down to epidemiological chance, but to real issues that require much deeper investigation.
Most of the doctors' work focuses on two areas: height and the distribution of body fat. "We've known for a long time that the taller you are, the higher your risk of breast cancer, prostate cancer, colo-rectal cancer, leukaemia and lymphomas," says David Gunnell, professor of epidemiology at Bristol University. "If you're short, on the other hand, we know you are more at risk of cardiovascular disease and strokes - that has been shown in many studies, including one published earlier this year that looked at 4,000 women and found those with short legs had more chance of getting heart disease than those with longer legs. And we know short men are at greater risk, too."
For a long time, says Gunnell, these statistical link-ups were merely puzzled over by scientists: but over the past decade or so clues have been found that may explain the findings, and that could in turn provide exciting new ways of screening and even treating disease in the future. What seems to be most significant, says Gunnell, is that being tall is an overall healthier shape to be - you might be more prone to cancer, but part of the reason for that is precisely that you are going to live longer and so are more likely to succumb to what remains, after all, mostly a disease of old age.
It has long been known that factors such as not being breastfed, having a poor childhood diet and being born into a less-affluent family influence growth negatively: what doctors now believe is that issues in early life - especially dietary issues - that affect height then go on to affect an individual's susceptibility to conditions such as heart disease and strokes. But, says Gunnell, what is also interesting is the role of blood-carried hormones called insulin-like growth factors (IGFs). High levels of these hormones, which are known to be an important determinant of childhood growth but which are also present in the adult bloodstream, have been strongly linked with prostate cancer and may also be related to breast and colon cancer; meanwhile, a study from Denmark has also found people with high concentrations of IGFs have a lower-than-average risk of heart disease.
The chemistry is still being unravelled but what is emerging on the cancer front is that, while IGFs are designed to boost cell turnover and so make a person taller, they also - as an unfortunate side-effect - seem to dampen the body's self-defence mechanism which is primed to force damaged cells to self-destruct. If these cells fail to bump themselves off, because of the influence of the IGFs, they may go on to become malignant. And it follows that a person with a high level of IGFs swishing around their bloodstream will have a greater risk of this interference happening and so a greater risk of cancer eventually developing.
What doctors are now starting to look at, says Gunnell, is the possibility of screening IGF levels in the bloodstream to pinpoint those who might be at higher risk of cancer; because of the effect of other factors, such as early nutrition, it isn't the case that only tall people have a higher proportion of IGFs, although they are more likely to have them than short people. Even more exciting than the screening, for the future, is the chance that IGF-blocking agents could be developed to counteract the hormone's effect on the body's defence mechanism, and so prevent some malignancies developing.
Some studies have shown it isn't just adult height that is significant: research published last week in the New England Journal of Medicine linked a higher risk of breast cancer with girls who were heavier at birth and taller aged 14. The reason isn't clear, but again IGFs could be involved: it may be that the amount of IGFs in the bloodstream during puberty is a significant factor in turning off one of the body's defence mechanisms at a crucial time.
But let's get back to your reflection, because it's not just height that's significant. A few days ago, the National Obesity Forum conference heard a bleak warning over the association between fat distribution and the risk of heart disease and diabetes: in a nutshell, the message is that being round and apple-shaped is not just bad, it's very, very bad. Get that tape measure out and check your vital statistics, says diabetes expert Professor Anthony Barnett of the University of Birmingham. If you're a woman with a bigger than 32 inch waistline, or a man with a bigger than 37 inch measurement, you could be heading for trouble: and if your waist circumference is even bigger - more than 35 inches for a woman, 40 inches for a man - you could be at four times the normal risk of developing diabetes and heart disease.
The health profession, it seems, is closely monitoring our changing body shape. Another survey, reported in today's papers, suggests that the average British male is now the not-so-proud owner of a beer belly of varying proportions, depending on which area of the country he lives in. According to the health and fitness website DailyDietTracker.co.uk, which surveyed 38,000 adults, the average male is now a distinctive "apple" shape, rather than, say, celery or leek shaped, with a worrying build-up of fat concentrated around the waist. Overall, women, the survey found, are still largely retaining their far healthier pear shape, with fat concentrated on the hips rather than the belly, though women in Northern Ireland, north east England, East Anglia and Wales are the most likely to be apples.
The problem, says Barnett, is that the waist is a bad area to lay down fat: far better to be big on your bottom and hips - the classic pear-shape - than thick-waisted. "What some people call big-belly obesity is usually because you're eating more food than you need and not burning it off by taking enough exercise," he says.
"We're not sure exactly why waist fat is so damaging, but we think it's because fat cells around the waist tend to be very active. Fat cells around the waist don't just sit there, they produce chemicals, and some of these chemicals seem to produce an imbalance of proteins and hormones that can damage the body's insulin system, putting you at risk of type 2 diabetes.
"It's especially bad news for women, because what we are seeing is that younger women - who traditionally lay down fat on their thighs and bottoms - are getting bigger tummies, as men have always tended to do." That, says Barnett, overrides the protection from heart disease and diabetes that women have tended to get from oestrogen before the menopause. In other words, if women go on getting bigger around the waist, the rates of heart disease among pre-menopausal females may soon be as high as those among men, rather than being significantly lower as they currently are. At the moment, 28% of men and 20% of women have waistlines that are way too big, and obesity forecasters warn those figures are likely to rise.
As well as indicating your risk of illness, your body shape can sometimes alert you to a condition you already have. People with Marfan's Syndrome, for example, are often not diagnosed until their illness, which causes a problem of the connective tissues, affects the heart and becomes life-threatening. But they may for many years have exhibited the tell-tale features of the condition, which affects one in 5,000 people in the UK: long limbs, a slim build, very long fingers and toes. "We hear tales of young people who go along to accident and emergency saying they have a bad chest ache, and they are sent home with painkillers and then die of an aneurysm the following day," says Marion Mason of Marfan Association UK. "But the signs will always have been there - they will be very tall, lanky individuals ... we need to make health professionals, as well as the rest of the population, a lot more aware of this."
Sometimes it is a change in body shape that can alert you to a problem. "We get lots of people who phone us because they have noticed a change in their body shape," says Sarah Leyland of the National Osteoporosis Society. "Typically, they would be older, post menopausal women, and what they have seen is that their shoulders have become more rounded and their height has shrunk - in some cases they think they have got bigger round the waist but that is actually because they are more stooped than they used to be.
"We advise them to go to their GP, who will be able to refer them for X-rays, because it may be that they have got osteoporatic fractures in their spine." What that means, says Leyland, is that the usually rectangular-shaped vertebrae in the neck and upper back become crushed into wedge-shaped structures, forcing the head forward and causing the shoulders to hunch.
"It tends to happen very gradually, but sometimes you just suddenly become aware of it," says Leyland. "Typically, we hear from women who have caught sight of themselves in the mirror and been really shocked at how they look - that's what prompts them to investigate what has gone wrong, because it can seem very dramatic."
