NYT reviews weight gain/loss research

[firecat]

The New York Times excerpts Gina Kolata’s new book, Rethinking Thin: The New Science of Weight Loss — and the Myths and Realities of Dieting reviews early human experiments on weight loss and gain. (free registration required)

http://www.nytimes.com/2007/05/08/health/08fat.html

A 1959 experiment on very low calorie dieting found that "fat people who lost large amounts of weight might look like someone who was never fat, but they were very different. In fact, by every metabolic measurement, they seemed like people who were starving....The Rockefeller subjects also had a psychiatric syndrome, called semi-starvation neurosis, which had been noticed before in people of normal weight who had been starved. They dreamed of food, they fantasized about food or about breaking their diet. They were anxious and depressed; some had thoughts of suicide. They secreted food in their rooms. And they binged."

and

Dr. Ethan Sims at the University of Vermont...asked what would happen if thin people who had never had a weight problem deliberately got fat.

His subjects were prisoners at a nearby state prison who volunteered to gain weight. With great difficulty, they succeeded, increasing their weight by 20 percent to 25 percent. But it took them four to six months, eating as much as they could every day. Some consumed 10,000 calories a day, an amount so incredible that it would be hard to believe, were it not for the fact that there were attendants present at each meal who dutifully recorded everything the men ate.

Once the men were fat, their metabolisms increased by 50 percent. They needed more than 2,700 calories per square meter of their body surface to stay fat but needed just 1,800 calories per square meter to maintain their normal weight.

When the study ended, the prisoners had no trouble losing weight. Within months, they were back to normal and effortlessly stayed there.

Comments

[fatfu.livejournal.com]

I think the evidence that Americans are "fatter" than other countries is a lot weaker than the evidence that Americans are fatter than we were. A lot of the international data compares apples and oranges (e.g. some nations only survey subsets of their populations; different protocols are used; some data is more up to date than others, etc...)

But the data is reasonably sound showing year to year changes within the U.S., because the CDC has been tracking BMI for about 40 or 50 years, using, AFAIK, more or less the same methodology across the decades. And there you see BMI increasing.

Unfortunately everybody points to that average increase in weight as evidence that it's "all environment." But that's bogus logic. The increase is only equivalent to about 7 lbs on average per person during the so-called "obesity epidemic". That's well within the "comfortable range" which people can gain or lose without major metabolic and appetite changes kicking in according to these studies.

And more importantly that increase of 7 lb is just a small nudge up of a bell curve that spans hundreds of pounds. So it's like saying a 5 point average increase in IQ means that all intelligence is purely environmental. That's ridiculous. IQ varies by 100 points or more, that you may or may not be able to nudge it in one direction or another doesn't mean it's infinitely malleable. The bell curve for height has also been nudged up over the past century. But everybody considers the environmental impact to be small compared to the genetic influence.

Most graphs that chart the "obesity epidemic" make the population changes look a lot more dramatic than they are, because instead of just comparing average or median BMI's, they use "percent obese." This creates a threshold effect, since the threshold for being labelled "obese" has always been very close to the peak of the bell curve. In other words a small change in BMI nudges a large fraction of the population from "overweight" to "obese" and you get a 5 or 10 lb average weight change increasing the number of obese by huge amounts (I think it's by 100% or so currently - something like that).

[libskrat]

Are these studies controlling for age? Because over the last 40 or 50 years the age-composition of our society has been skewing older, and older people tend to weigh more.

[fatfu.livejournal.com]

Yeah, they're age-adjusted.

[bastette-joyce.livejournal.com]

One reason "Americans are getting fatter" (than we were) is that the Baby Boomers are aging. Lots of people gain weight as they age, and since this population is so large, it's affecting the national average noticeably.

And, I've said this a lot because many people seem to forget it (probably not people reading this, because most size activists have been paying attention to this), but 9 years ago, the national threshold for "obesity" was lowered, allowing millions of people who were merely "overweight" to become "obese" overnight. Unless that change is adjusted for, it just looks like there was a sudden jump in fat people over the past decade.

It would be interesting to get real data on weight statistics from other countries, particularly from countries that are similar to the US - ie, Westernized, industrial, and wealthy countries - that would have similar conditions to ours, so comparisons would make some sense.

The bell curve for height has also been nudged up over the past century. But everybody considers the environmental impact to be small compared to the genetic influence.

Actually, 100 years would have no impact whatsoever on the overall genetic change of a population (unless there was some sort of cataclysm, weeding out all but a few members of the population). So the fact that we're taller than we were 100 years ago actually is due to environment - specifically, changes in our diet. (More meat protein, I think.)

[mjlayman.livejournal.com]

I have a friend who has been actually skinny, not average, for the more than a decade that I've known him (people who've known him longer knew him as very fat and he reads Usenet while on a treadmill to maintain his lower weight) and he's actually "obese" by BMI standards. Makes you wonder.

[jenk]

The increase is only equivalent to about 7 lbs on average per person during the so-called "obesity epidemic". That's well within the "comfortable range" which people can gain or lose without major metabolic and appetite changes kicking in according to these studies.

Not to mention that the "obese" BMI was moved from >32 to >30 in 2000. On 5'9" me, a change of 7lbs is a change in 1.1 on my BMI.