My, aren’t you a tall lassie!
She’s taller than her dad, isn’t she?
She’s like her cousin. Now there’s a big woman.
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It must be something in the water. Folk weren’t like that in my day.
A GAGGLE of grannies inspects me at a family wedding. Looking around the room, it is striking how the generations are stratified. True, people do tend to shrink a bit as they get older. But even so, something dramatic has happened in the years since my grandparents were dancing at their own wedding under the shadow of the second world war.
The past half-century or so has seen remarkable changes in the shape and size of our bodies. People are taller than they once were, and rounder too, thanks to our liking for junk food and indolence. While these facts come as no surprise, there are some unexpected changes too. The entire make-up of our bodies is changing, and not for the better. What is more, the notion of what an ideal body should look like has shifted in the opposite direction to reality. Today’s curvy woman and slightly chubby man are much more like the sex symbols of yesteryear than the beautiful people of 2004 (see “Vital statistics”).
As any granny will happily tell you, young people are tall these days. In fact, in industrialised nations they have been getting taller for decades (Proceedings of the Nutrition Society, vol 59, p 317). The people of the Netherlands, now the world’s tallest, have been on an upward trend since 1851, though the rate of growth accelerated after the second world war. In 1965, the average Dutch man was 1.78 metres tall. By 1997, he was 6 centimetres taller. The average Dutch woman grew from 1.66 metres to 1.71 metres.
Europe’s shorter people, mainly those in the south, have shot up too. The Spanish grew by 2.4 cm per decade between 1960 and 1990. And though there are signs that the rate of growth in western Europe is tailing off, with rates typically 1 cm or less per decade, people elsewhere are still shooting up. Eastern Europeans and the Japanese are achieving rates of up to 3 cm per decade. Intriguingly, women have grown at a slower rate than men, meaning that the sex differences in height have widened.
So what is behind these trends? You might think it is all down to better nutrition. But the answer is not that simple. It turns out that what really matters is how fast you grow in the first year or two. This is the crucial period that determines how tall you will be as an adult – and it is not all to do with food.
The first two years are key because this is when you are growing fastest. In particular, the long bones in your legs are extending rapidly, and it is leg length more than anything else that dictates your final height. This early spurt is what makes it harder for a child to “catch up” if he or she has had a slow start.
Clearly, improved nutrition and the other trappings of affluence have an effect on how fast infants grow. The Japanese are a case in point. Following the second world war, Japan underwent a period of rapid socioeconomic development. The average 17-year-old Japanese boy was 5 cm taller in 1980 than he was in 1948, and the average 17-year-old girl was 4 cm taller (American Journal of Clinical Nutrition (suppl), vol 72, p 1379S). Health is also a key factor. Until the advent of modern antibiotics and vaccines, infection seriously stifled babies’ growth. Today’s parents fret over media scares about combined vaccines; parents in the 1940s prayed over the cribs of infants stricken with diphtheria, whooping cough and polio.
Still, this cannot be the whole answer. Look at the Dutch. Even assuming that they have reached their full genetic potential, it has taken several generations for them to do so. If conditions got so much better after the war, why did it not happen in a single generation?
Part of the answer might be that overly rapid growth in infancy puts you at risk of disease in later life (see “Life sentence”). Tim Cole, professor of medical statistics at the Institute of Child Health in London, speculates that there may be mechanisms to limit growth rate for this reason. Another reason is the fact that your height depends on how tall your parents are – or, more accurately, how tall they aren’t. If they did not attain their full potential, chances are you won’t either. It seems that the height both parents managed to reach somehow affects how tall their children can grow. There are even hints that the effects span more than one generation – your grandmother’s height also has some influence. So if you think you are a bit on the short side, blame your parents and your grandparents, and maybe even your great-grandparents, too.
“If you think you’re a bit on the short side, blame your parents and grandparents”
So environment plays some role in determining our height. And it has certainly changed our weight. Part of the increase in weight can be explained by the fact that people are taller than they were 50 years ago. That is why scientists studying these trends talk about weight in terms of body-mass index, or BMI: it is a way of factoring in height when considering someone’s ideal weight.
You can calculate your BMI by dividing your weight in kilograms by the square of your height in metres. A BMI of less than 18.5 is considered underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight or “pre-obese”, and anything above 30 is classified as obese.
The fact that obesity is reaching epidemic proportions in the west is hardly news, and neither is the fact that the US is the worst affected. Based on BMI, obesity rates in the US remained stable from 1960 to 1980 at around 13 per cent in men and 17 per cent in women. But by 1991, 21 per cent of men and 26 per cent of women were obese. Now more than a quarter of American men (28 per cent) and about a third of women (34 per cent) are obese, and according to the National Center for Health Statistics, nearly two-thirds of American adults are at least overweight.
The rest of the western world has little to feel smug about. In the UK, 38 per cent of women and 44 per cent of men are overweight or obese. In Australia, some 19 per cent of men and 22 per cent of women are obese, according to the International Obesity Task Force figures. And according to the World Health Organization, more than 1 billion adults around the world are overweight, with 300 million of them obese.
But BMI is only telling half the story. If you look at other ways of measuring obesity, an even sorrier state of affairs quickly appears.
The problem with BMI is that it fails to capture how fat is distributed in the body. This is important because fat distribution is a major determinant of health. People who have a high level of “abdominal adiposity”, which means they carry a lot of fat around their midriffs and upper bodies, are at much greater risk of developing type 2 diabetes and of having high levels of unhealthy fats in their blood. Both of these increase the risk of heart disease. żěè¶ĚĘÓƵs are not sure why this happens, but think it may be related to the fact that people who carry fat around their midriffs also tend to have a lot of fat around their organs. These visceral fat depots seem to be more prone to releasing fats into the bloodstream than do fat stores elsewhere in the body.
A better measure of abdominal adiposity comes from measuring waist circumference, and a number of recent studies have highlighted how people in developed nations are becoming increasingly apple-shaped.
In one study, a team led by Ike Okosun at the Mercer University School of Medicine in Macon, Georgia, charted how the waist circumference of American adults has changed since the 1960s (Preventive Medicine, vol 39, p 197). What they found was startling. Between 1960 and 2000, the mean waist circumference for men went up by 9.9 cm, while that of women leapt by 23.2 cm (see Graphic). The percentage of people with abdominal obesity, defined as having a waist circumference of 88 cm or greater in women and 102 cm or greater in men, trebled in both men and women. Almost 40 per cent of men and 60 per cent of women in the US are now defined as abdominally obese. Compare that with BMI-based figures of 28 per cent and 34 per cent. Most tellingly of all, even people with a BMI below the obesity threshold tend to have larger waists today than they did in the 1960s. So you could have a healthy BMI and yet still be at risk of disease due to abdominal fat.
The British, too, are getting decidedly pot-bellied. According to a recent survey of body shape called Size UK (see “Retail therapy”), the waist measurement of the average woman has increased from 70 cm in 1951 to 86 cm today. “Everybody looks pregnant,” laments Philip Treleaven of University College London, who led the study. There is no data for men’s waist measurements in 1951, but today’s Mr Average has a 94 cm waist. Similar surveys are under way or planned in Australia, France, South Korea, Brazil and Mexico.
As well as worrying about what we are putting on, perhaps we should start thinking about what we are taking off. In studies looking at how BMIs and waist measurements have changed, researchers have noticed a puzzling trend. Fatness, as measured by waist circumference and skin-fold thickness, is increasing significantly faster than BMI. So although we are putting on more fat, our weight is not rising by the same proportion.
That might sound like good news, but it is not. What it means is that as we gain fat, we are losing something else. And now researchers studying body composition have discovered what that something is: lean mass, or muscle. Muscle is denser than fat, hence the discrepancy between BMI and fatness. In other words, our muscles are shrinking and being replaced by fat.
The trend is particularly worrying in children. Two years ago Jonathan Wells, a nutritionist at the Institute of Child Health, investigated how the body composition of children had changed from the mid-1970s to the 1990s (International Journal of Obesity, vol 26, p 1323). What he found was surprising.
First the good news. The BMI of children aged up to 10 years has barely changed. The findings for body composition, however, tell a different story. “What we did see was an increase in fat and a loss of lean mass,” says Wells. On average, 1990s boys had 23 per cent more fat than their counterparts 20 years earlier and girls had 35 per cent more. Lean mass decreased by 3.2 per cent in boys and 3.6 per cent in girls. This loss of lean mass means that children are building less muscle as they grow – especially worrying, as properly developed muscles are essential for the formation of strong bones. “So even if children stay the same weight over time, they may be less healthy,” says Wells. “The obesity epidemic may be worse than you think.”
A number of other studies have come to a similar conclusion. David McCarthy at London Metropolitan University compared waist measurements from a 1997 survey of British children aged between 11 and 16 with those of boys from 1977 and girls from 1987 (British Medical Journal, vol 326, p 1). They found that the boys’ waist measurements had jumped by 6.9 cm and the girls’ by 6.2 cm. “It corresponds to two or three notches on a belt,” says Cole, who analysed the statistics for the study. “This fits in with one’s perception. It’s trendy for girls now to expose their midriff, and of course, their midriff is usually bulging in a way in which certainly it didn’t even 10 years ago.” Like other researchers, McCarthy found that the rate of increase in fatness outstripped that of BMI, indicating a loss of muscle mass. Other studies in the US and Spain have had similar results. McCarthy’s team say they have also seen increases in children as young as 3, although they have yet to publish the figures.
“It’s trendy for girls to expose their midriff, and of course their midriff is usually bulging”
There are no prizes for guessing why all this is happening. Not only are we eating more food; the quality of what we eat is poorer. Our 24/7 culture leaves little time for anything other than convenience food, which is high in fat and sugar and low in nutrients. “You can consume an awful lot of calories without much nutrition in a small package now,” says David Porter, a World Health Organization spokesman on diet and chronic disease.
Our sedentary lifestyles have a lot to answer for, too. In fact, some scientists argue it is a far bigger problem than excess calories. A survey carried out in 1996 by the US Centers for Disease Control showed that nearly half of girls and over a quarter of boys do not take regular exercise. A quarter of US children watch more than 4 hours of TV a day.
Towering above a little sea of blue rinses, I wonder how different our lives are today compared with the old days of cold baths, junket and powdered egg. Looking around the room, I can see how history has been recorded in the different shapes and sizes of our bodies. Not that that will stop me scoffing another load of champagne and wedding cake, ofcourse.
Retail therapy
THE dramatic changes in our height and body shape over the past 50 years has caused a headache for retailers: the clothes they make don’t really fit us any more. To deal with the problem, a group of UK retailers commissioned a survey of 11,000 British people using 3D body scanners.
The scanners use stripes of laser light to capture an image of a person, dressed only in their underwear, to build a 3D map of the body surface. Each map takes only seconds to complete and, because it is 3D, it allows measurements to be made that were simply not practical before. “This is the wonderful thing about scanners,” says Philip Treleaven, director of the Size UK survey and professor of computer science at University College London. “You are capturing people’s shape.”
And body shape is becoming increasingly important for medical researchers. The scans could help, because information they yield can be analysed in great detail, says Treleaven. For example, the curvature of a person’s abdomen may prove to be a better measure of abdominal fatness than their waist measurement alone.
Hopefully, women’s clothes – which are still modelled on 1950s women – will start to fit better too. But the chances are that even the most advanced body scanner won’t stop your bum from looking big.