April 21, 2009

Phthalates Make Us Fat[ter]

The dangers of phthalates (an ingredient in some plastics) as an endocrine disruptor are well-known. Now we discover, via a study conducted by Mt. Sinai Hospital, that they may in fact play a role in the childhood obesity epidemic. Ezra Klein however is unimpressed:
Thirty years ago, kids might have been sedentary and eating lots of crappy food, but they were eating less of it than they are now. Same for adults. According to CDC data, between 1971 and 2000, obesity in the United States shot from 14.9% to 30.1%. The main reason is simple enough: Average calorie consumption increased. Men went from 2,450 calories to 2,618 calories. Over the course of a year, that's an increase in 61,320 calories. The trends were even more striking for women: an average intake of 1,542 calories became 1,877 calories. That's 122,275 extra calories per year. (The gender difference here surprises me, incidentally.) Another study, this one from the USDA, estimated that "average daily calorie consumption in 2000 was 12 percent, or roughly 300 calories, above the 1985 level." This, they estimated, was the prime factor behind America's soaring rates of obesity and Type 2 diabetes.
But Mrs. Beyond Green, a political scientist who studies public health issues, thinks Ezra is too quick to dismiss the potential role of phthalates. She points out that:
It may seem like calories in-calories out is the obvious, clear answer. But I think we actually don't understand the hormonal regulation of metabolic functions all that well, and so it seems PLAUSIBLE that the obvious answer may actually be wrong. It may be that eating a lot more calories makes us fatter, but that absent any other disruptions to the metabolic system, most people would eventually adjust to the new calorie load without becoming morbidly obese -- just a little bit fat. Enter phthalates (and whatever other junk is out there). It disrupts something in the metabolic balance and causes us to be unable to adjust to the new calorie load.
One thing that's worth noting in the Mt. Sinai study is that we don't know the calorie intakes of those kids. It could be that high exposure to phthalates (and these kids had much higher than average levels of phthlataes present in their urine) causes obesity at caloric intake levels that might only be slightly above normal. Ezra does, of course, agree this should be studied further, but thinks the focus needs to remain on diet. At the same time, he also points out, dealing with the diabetes epidemic may be beyond the capacity of our (or any) health system:
[N]o one knows how you provide affordable medical services to a population where a solid quarter of the folks have type II diabetes. In fact, you probably can't do it. But that's where the trends are headed.
Given the threat that diabetes represents to the system (not to mention to our health), it seems like even marginal contributors should be quickly addressed. Phthalates (along with their evil plasticizing brethren) may well have turned what might have been a manageable problem into an existential crisis.

Photo by Steve Wampler used under a CC license

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Anonymous Anonymous said...

The Mt Sinai study is actally the third epidemiological study to report a link between obesity and phthalates.

There is a lot of research underway exploring the potential role of contaminants in causing obesity and type 2 diabetes. Most is experimental with animals and cells (including humans). And guess what, some contaminants do cause obesity, particularly following fetal exposure.

There's an excellent video on line with one of the leading molecular geneticists in the world who works on this explaining one mechanism: certain contaminants, including phthalates, turn on a gene that increases the likelihood that a stem cell will become a fat cell.

You can watch Dr. Bruce Blumberg here:

Anonymous Adam Wolff said...

This is interesting, but I'm with Ezra Klein (whoever that is.) Stop eating so much $%^&* food people and get some exercise!

Anonymous Anonymous said...

Unfortunately, you are missing a very important point regarding the obesity link.

Many hormone mimickers -- endocrine disruptors -- are negatively impacting the hypothalamus in the brains of humans. The hypothalamus is the area of the brain that regulates the thyroid and other endocrine glands that determine our growth rate, energy levels and metabolic rates. In addition, the hypothalamus is the control center that regulates appetite and the sensation of fullness and the number of fat cells that are created. If the hypothalamus is compromised by synthetic, disruptive chemicals a person may feel tired and hungry all of the time, even when they've just eaten. The hypothalamus may also send mixed signals to fat cells telling them to increase their numbers. If the brain -- the hypothalamus -- is damaged by these insidious chemicals, obesity may result.

A damaged hypothalamus may cause a person to gain weight (and slow their metabolism) even though the individual may eat the same amount of food as a thinner person.

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