The difference between causality and correlation is fairly important

We’ve a new report stating that obesity is making us all poorer:

Areas in England with the most overweight and obese people also have the lowest rates of productivity, according to research showing “obesity is an economic as well as a health timebomb”.

Conversely, places with the highest gross domestic product (GDP) per head have much lower proportions of citizens who are dangerously overweight, the analysis shows.

Well, yes. The report then goes on to suggest that if we reduced the obesity rates then GDP would be higher and we’d all be richer. It’s that second bit which isn’t obviously so.

There’s the usual mistake of course, obesity is seen as a cost to the NHS. As we’ve pointed out many a time before when we have a lifetime health care system it has to be lifetime health care costs which are used to calculate the costs of any particular disease, affliction or condition. And the obese do indeed die earlier (well, the morbidly obese, on average) and as it works out this reduces lifetime health care costs. As do drinkers and smokers. We all do gain - yes, despite current complaints - end of life health care from the NHS and it’s not obvious that those costs are greater for those who have over-indulged in any of the trio of booze, tabs and doughnuts. But that dying earlier reduces the number of years that standard health care costs have to be carried - overall shorter lifespans save the NHS money.

We’ve also a new and interesting mistake here.

Obesity tends to be associated with poverty in our society. That’s one measure of how rich it is, of course. Until perhaps a century ago only the rich could even afford to be fat. But we also tend to think that people are paid their marginal productivity. Which means that incomes are lower in areas with lower productivity. Also, lower incomes means people are poorer by that national comparison.

So, what we’ve really found here is that there’s a correlation between relative poverty and relative poverty. Lower GDP, relative poverty and diseases - or conditions - of poverty are correlated.

It’s, umm. something of a leap to then conclude the causality runs from the obesity to the relative poverty. Possibly even a vaulting over a chasm in the logic.

To be very polite about this let us say that we’re less than convinced about that final step there. For the conclusion is that if we were slimmer then we’d be richer. And, well, obesity rates are very much lower in very poor societies, so we’re really unconvinced that it does work that way.