Sugar isn’t the problem?
This week’s installment in the stream of stories that have found The Answer To Obesity says the problem isn’t just diet or exercise, it’s plastic bottles. The Herald says
Man-made chemicals present in homes, schools, offices, cars and food are probably contributing to the sharp rise in obesity and diabetes in Western societies, according to a review of scientific literature published yesterday.
Until now lifestyle factors such as lack of exercise and poor diet were believed to be the primary causes of the increased incidence of both conditions, whose proliferation has strained global health budgets.
If you separate out diabetes, it’s not true that obesity has strained global health budgets. The incidence of heart attacks, for example, continues to go down all over the world. The rate of decline has slowed a bit, but increases are still theoretical and aren’t straining anything. However, if we stipulate that obesity is bad, are bisphenol A, PCBS, and phthalates responsible?
All 240 studies they reviewed – whether in test-tubes, on animals or on humans – had been peer-reviewed and published in scientific journals.
While substantial laboratory evidence shows chemicals can affect weight gain in animals and therefore supports the hypothesis that EDCs promote or otherwise influence obesity (see Table 1 above), the evidence in humans is still limited
They go on to say that it’s hard to assess cause and effect, since body fat absorbs and stores many of the relevant chemicals, and that the relationship between dose and effect might be complicated. That is, they think there is an excuse for not seeing much evidence in humans at realistic doses, just in animals at high doses.
We know that increases in food sold in the US are sufficient to explain increases in average weight, and if chemicals are relevant, it must be mostly through effects on appetite rather than on metabolism. It’s possible, based on the studies in small furry animals, that the chemicals the report worries about do have a non-zero effect on diabetes and obesity, but it does not seem plausible that it’s a substantial component of the global trends.
The Herald story said
Until now lifestyle factors such as lack of exercise and poor diet were believed to be the primary causes of the increased incidence of both conditions.
Until now. And subsequently.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »
That “Until now” sentence – almost teeth grindingly annoying that was.
12 years ago