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That ‘being overweight is good for you’ story…

by Henry Scowcroft | Analysis

27 November 2007

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ScalesSo we’ve given the obesity debate considerable coverage on here and you’re probably all fed up with it by now.

But it would be wrong for this blog to ignore recent (and somewhat alarming) reports that ‘being overweight was good for you‘.

The headlines were due to a research paper that, in essence, compared what people died of, against how heavy they were.

It found that people who were overweight (but not clinically ‘obese’) actually appeared to have a lower death rate than people who have a normal bodyweight, or who are clinically obese – particularly for causes of death other than cancer or heart disease.

This got reported in the Independent as “Now doctors say it’s good to be fat“.

This flies in the face of a rather extraordinary amount of evidence. Is it ‘good’ science?

Well, sort of. But there are a number of things about the study that make its findings not completely reliable:


Backwards-looking studies like this one, which look at events that happened before the study was set up, are less reliable than forward looking, ‘prospective’ studies, which follow people over their lives and see what happens. And the results of a huge, prospective study in 2003, looking at death rates and bodyweight, found that death rates increased with increasing weight.

Assumes BMI = ‘bodyweight’ in the elderly

Other studies have questioned whether the use of BMI (your weight, in kg, divided by height squared, in metres) in older people is really a good way to measure ‘obesity’.

Doesn’t prove causality

The study suggests that lean people are more likely to die than overweight people, but ignores the fact that sickness often makes people leaner. Even conditions that result from obesity, like cancer and heart disease, eventually lead to weight loss.

Results might be skewed by injury

The ‘non-cancer, non-heart disease’ group of deaths includes fatal injuries, which can’t help but skew the results, since studies repeatedly show that obese people are less likely to be out and about, and less likely to be involved in accidents or, for example, be murdered.

Doesn’t account for Quality of Life

Another very important point to make is that living longer, in itself, is not necessarily a good thing. Quality of life is the important thing, as this blogger pointed out:

“While it’s safer on the couch popping bon-bons and ACE inhibitors [heart disease drugs], that doesn’t make for an excellent life plan.”

But regardless, the big question is: does it matter? For cancer, not a jot. For a start, the paper says that obese people are more likely to die from cancer, and obesity accounts for about 14,000 deaths a year in the US.

Furthermore, the body of evidence that overweight AND obesity increase cancer risk cancer is so strong, so well established and so long-in-the-making that we would be foolish and remiss if we ignored all that on the basis of one statistical analysis.

We’re talking about a risk factor that causes 12,000 cases of cancer in the UK every year.

This paper in no way invalidates the vast body of evidence which says that overweight and obesity cause cancer.

Henry and Ed