Saturday 19 March 2016

Diets and incomes

Bryony Gordon has written a piece for the Telegraph about what she perceives as snobbery in the sugar tax debate.

What’s worse than the sugar tax? The pretentious, condescending presumption that it is a tax on the poor - a presumption that, by extension, implies that anyone without money belongs to some braindead underclass incapable of making intelligent choices.

I would argue that most of the snobbery comes from the 'public health' lobby, but she has a point when she says...

The idea that only the underprivileged eat rubbish is insulting to those on the breadline who are perfectly capable of making a meal from scratch -  sugar is clearly not so bad if it is packaged by Green and Blacks.

There is certainly a perception that consumption of junk food and fizzy drinks is confined to the poor and that people on low incomes are vastly more likely to be obese than the middle classes.

A few years ago, Anna Soubry got herself in hot water when she made a comment about obesity and poverty...

“When I go to my constituency, in fact when I walk around, you can almost now tell somebody’s background by their weight,” she said. “Obviously, not everybody who is overweight comes from deprived backgrounds but that’s where the propensity lies.” 

I reluctantly came to Soubry's defence. She had exaggerated, but her basic point was correct. There is a socio-economic gradient with obesity. Rates are highest amongst the poorest and lowest amongst the richest. The data show that...

For women, the proportions who were obese were higher in the lowest income quintiles (26 per cent - 31 per cent) and lower in the highest quintiles (15 per cent - 18 per cent).

For men, the proportions who were obese were also higher in the lowest income quintiles (29 per cent - 30 per cent) and lower in the highest quintiles (23 per cent - 24 per cent).

The proportion of women with a very high waist circumference was lower in the highest income quintiles (36 per cent - 39 per cent) and higher in the lowest income quintiles (47 per cent - 54 per cent).

The proportion of men with a very high waist circumference was also lower in the highest income quintiles (30 per cent) and higher in the lowest income quintiles (39 per cent to 42 per cent).

The difference is starkest amongst women. Obesity rates are nearly twice as high at the bottom end of the income spectrum than at the top. Amongst men, the difference is quite small. For every four obese men in the highest income group, there are five obese men in the lowest income group.

So while there are clearly differences, it would be easy to exaggerate them (as Soubry did), particularly with regards to men.

But if we look at diet, there are very few differences. The data show that...

Both low income households and all households have a relatively similar diet when compared to the eatwell plate.

The National Diet and Nutrition Survey (NDNS) looks at food consumption in detail. The usual caveats about self-reported consumption apply, but this is what the survey shows for total calorie intake in each income quintile...

As you can see, there is not a lot of difference. Insofar as there is a trend, it is for richer people to consume more calories.

The NDNS also has figures for 'non-milk extrinsic sugars' - that's added sugar to you or me. Here the differences are somewhat more marked, although it is the middle income quintile that consumes the least. The poorest quintile consumes around 20 per cent more than the middle quintile.

This is not mirrored amongst children, however. The graphs below show sugar consumption for boys and girls aged 11-18 years (the figures for 4-10 year olds are not dissimilar) .

Looking at other food groups, there are also few differences. Carbohydrate consumption is virtually the same across all groups, as is total fat consumption, but the richer groups consume slightly more saturated fat and protein.

The NDNS does not hold information for sugary drinks but evidence from the USA suggests that low income groups tend to consume more of them. It also appears that low income adults - but not their children - consume more sugar than average. But overall, the poorest groups consume fewer calories than middle and high income groups. This is true for men, women and boys. For girls, energy intake is similar across the board.

The belief that different socio-economic groups have radically different diets is therefore misplaced, as is the belief that people on low incomes consume more calories. Once you strip away scientifically meaningless terms like 'junk food' and look at food groups, there are few differences.

To be clear, the regressive nature of a sugar tax is not dependent on low income groups consuming more sugar. As an indirect tax, it is bound to be regressive unless rich people consume vastly more of the product in question, which is not the case here.

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