There’s an amusing letter in today’s Financial Times. It reads:

Sir, Your leading article "Unfit for purpose" (March 17) poses the question: "How fast do you have to run to catch the average thief?" in the light of the Winsor Review's finding that three-quarters of the UK's male police officers are overweight or obese and need fitness testing.

Surely due diligence requires that you establish the same statistics for the criminal community. If the burglars and muggers are equally representative of the wider population in their corpulence, then perhaps the contest is not so unequal and our porkier coppers can be spared the crash diets the Winsor Review seems to be recommending.

Richard Baglin, London SE10, UK

Happily, there may be an answer to Mr Baglin’s question. A study (1) in the press at the journal Economics and Human Biology seeks to answer this very question, under the title “The association of obesity with the likelihood of arrest for young adults”. It’s by David Kalist and Freddy Siahaan of Shippensburg University in Pennsylvania, so it deals with US adults, but there’s no reason to suppose the findings aren’t applicable here.

It turns out there is a long history of studies in this genre, tending to find that criminals are more likely to be mesomorphs – solid and muscular, with body mass indices ranging from 19 to 25. A 2008 study found that 68.6 per cent of prisoners fell into this category, and that mesomorphs were more likely to be convicted of violent crimes than those with other body types.

What about the fatties? The British psychologist Hans Eysenck in Crime and Personality (1964) remarked: “The fat boy cannot fight and he cannot run away so he might just as well be friendly and sociable. Similarly, we might expect the mesomorphic boy to be more adventurous simply because his strong musculature enables him to be aggressive.”

The findings of Kalist and Siahaan confirm this. Using data from the US National Longitudinal Survey of Youth 1997 and following up the histories of almost 9,000 men and women until 2008, they find that the odds of an obese man being arrested are only 64 per cent of those of a man of healthy weight. For women, the effect is smaller: the odds of an obese woman being arrested are 78 per cent of those of women of healthy weight. For white men, they find, each one unit increase in BMI reduces the odds of being arrested.

Given that obese people are easier to identify, and much easier to catch, these odds ratios may underestimate the benefits of being fat. Indeed, the benefits should be set against the many drawbacks, both social and medical, of putting on weight. “The social costs of obesity may be overstated, as evidenced by the negative relationship between obesity and the probability of arrest” they conclude.

If true, this suggests that the perpetrators of crime will have the lean and muscular look. To catch them, the police will indeed need to be fitter than the Winsor review found them to be. More time in the gym and less in the canteen is called for.  

1. The association of obesity with the likelihood of arrest for young adults, by David E. Kallist and Freddy Siahaan, Economics and Human Biology (2012) doi: 10.1016/j.ehb..2012.02.001