Weighing the arguments

Obesity is fast becoming the number-one health issue in the UK. As our bellies and bottoms have expanded, we are told, so our health has deteriorated. Have our lifestyles changed so much over the past 10 years that they are now a threat to our wellbeing?

The UK chief medical officer’s annual report in July 2003 baldly stated the facts about obesity: ‘Obesity levels in England have tripled in the past two decades; around a fifth (21 per cent) of men and a quarter (24 per cent) of women are now obese, while almost 24million adults are now overweight or obese.’ The report notes that ‘obesity is also rising among children – in the five years between 1996 and 2001, the proportion of obese children aged 6 to 15 years rose by some 3.5 per cent.’ (1)

According to the report, the consequence of rising levels of obesity is an epidemic of chronic disease. ‘Worldwide, around 58 per cent of type-2 diabetes, 21 per cent of heart disease and between 8 per cent and 42 per cent of certain cancers are attributable to excess body fat.’ (2)

What is obesity? It is now commonly defined as a body-mass-index (BMI) of 30 or over. BMI is a ratio of weight-to-height. ‘Normal’ BMI is between 20 and 25. For a man of UK average height (5 feet 9 inches), a normal BMI equates to a weight of between 10 and 12 stone, and ‘obese’ would be about 14-and-a-half stone or more (3).

However, since terms like ‘overweight’ and ‘obese’ refer to thresholds, it is important to note that such thresholds are subject to change. What is defined as overweight and obese changes over time, and may bear no relation to commonly held notions of fatness. For example, in the UK, 67 per cent of people are officially categorised as overweight – so people of ‘average’ weight are also ‘overweight’ (4). While this may make sense against some medical standard, is it common sense?

There has also been a blurring of the categories of ‘overweight’ and ‘obese’. Many reports, like the chief medical officer’s, quote figures for the number of people who are overweight and then talk about the health risks of obesity – failing to mention that there is little or no evidence of any harm arising from being merely overweight.

Rapidly increasing rates of obesity have disguised relatively small changes in weight. Only a small increase in average weight is required for a lot more people to pass the threshold for one of the definitions described above. Statistics from the Department of Health indicate that while the percentage of people who are obese in England and Wales has risen from 13 per cent in 1993 to 21 per cent in 2001, the actual increase in average weight has been less than eight pounds, or one pound per year (5).

In lifestyle terms, putting on eight pounds over eight years amounts to consistently eating very slightly too much, or exercising slightly too little. On that basis, living in a world where food is seemingly available 24/7, where manual work has largely been replaced by pen-pushing, and where transport usually means four wheels rather than two legs, it seems remarkable that we haven’t put on more weight.

Given that life expectancy continues to increase, can such a small change in lifestyle really have a devastating impact on health?

According to a National Audit Office (NAO) report, ‘Evidence from studies suggests that for young adults in general the risk of mortality for someone with a BMI of 30 is about 50 per cent higher than that for someone with a healthy BMI (20 to 25) – and with a BMI of 35, the risk is more than doubled’ (6).

The crucial phrase here is ‘young adults’. Between the ages of 15 and 34, the chances of dying in any particular year are about one in 500. The equivalent figure for those over 65 years old is one in 16 – that is, 30 times greater. Even if a young adult’s risk of dying is doubled by his or her weight, it is still very unlikely they will die so young. Age is a far more significant factor in mortality than obesity (7).

Also, the figures in the NAO report are correlations. They do not explain causes. So, for example, fatness might cause premature death. Or, it could be that another factor causes both fatness and early death. If someone has a pre-existing heart condition for example, he or she might be discouraged from taking exercise, causing them to put on weight. In such a case, it would be strange to blame the weight gain for their demise.

Other evidence suggests that it is a combination of lack of exercise and obesity that is important. Fat people who manage to stay reasonably fit seem to have a risk of mortality little different to people of normal weight. Simplistic ideas like ‘obesity is responsible for more ill health even than smoking’ do not stand up to scrutiny (8).

There is stronger evidence of a link between obesity and type-2 diabetes. However, at present, diabetes is also more strongly linked with age than anything else. In England and Wales in 1998, over eight per cent of people aged over 65 had diabetes, compared to 0.5 per cent of 25- to 34-year-olds (9).

In the developed world, we are not dying from the kind of infectious diseases that were prevalent in the past. We tend to die more often from chronic diseases, like coronary heart disease and cancer, because we live long enough to have them. They are generally diseases of old age. Lifestyle has, at most, a small part to play.

Of course, if we carry on putting on weight as we have been doing, we will all be waddling around in extremely baggy clothes before long. Many of the factors which moderated weight in the past are now gone. We can eat as much as we like, pretty much whenever we like, while at the same time we can avoid physical exertion.

This means that we need consciously to control our weight more than ever. But the best reasons for doing so are much more personal: to fit into particular clothes, to get around more easily, or simply to feel better about ourselves. And if we prefer eating well to looking good, that’s okay too.

Yet, the UK government in its wisdom has spent millions on anti-obesity measures since 1997. These campaigns and interventions have been a complete failure. Moreover, they serve to increase anxiety and create a fixation with food that really is unhealthy.

Obesity is unlikely to shorten our lives very much and, if it does, it will almost certainly only affect us after we have starting collecting our pensions. So, eat, drink and be merry – life’s too short for worrying too much.

Read on:

Weight watchers, by Rob Lyons

(1) Annual report of the Chief Medical Officer 2002, UK Department of Health

(2) Annual report of the Chief Medical Officer 2002, UK Department of Health

(3) See What is BMI?, US Centers for Disease Control and Prevention for an explanation of BMI and a BMI calculator.

(4) Health Survey for England, UK Department of Health

(5) Health Survey for England, UK Department of Health

(6) Tackling Obesity in England, UK National Audit Office (pdf)

(7) Death rates by age, and sex, 1976-2000, UK Office of National Statistics (Excel spreadsheet)

(8) Medical notes: obesity, BBC News, 14 October 2003

(9) Prevalence of diagnosed diabetes: by sex and age, 1998, England and Wales (Excel spreadsheet)