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...the implication seems to be that Americans walking less somehow has a causative effect in skyrocketing obesity rates. This seems entirely wimpy and facile.

The fact that exercise causes weight loss has been borne out by numerous controlled experiments. Something I found via a quick search: https://docs.google.com/viewer?url=http%3A%2F%2Fwww.duke.car...

Also, Taubes' insulin nonsense has been debunked. Lets move on.

http://wholehealthsource.blogspot.com/2011/08/carbohydrate-h...

As for your hypothetical environmental cause, it must be extremely selective. For example, consider mixed income American neighborhoods (e.g., Harlem, Jersey City). This alleged environmental cause seems to primarily affect the lower income people. How does that happen? Are the yuppies with gym memberships and hipsters with their organic vegan raw paleo diets somehow immune?

> Are the yuppies with gym memberships and hipsters with their organic vegan raw paleo diets somehow immune?

Well, yes. As a paleo dieter, I can tell you I can't be eating more sugar than someone from the 1850s. My guess is that anyone conscious enough to be on a raw-vegan diet, doesn't either.

> This alleged environmental cause seems to primarily affect the lower income people.

My understanding is that refined carbohydrates and vegetable oils are cheap. Who was it that said that if you have $1.5 to spend on food, you're better off (calorically) buying potato chips than broccoli.

> Also, Taubes' insulin nonsense has been debunked. Lets move on.

I do suspect that it's simplistic. It's much better than the popular notion of calories-in/calories-out, though. That's why I said that it's controversial, but that it's the kind of thing, that's more on-the-mark than simply blaming sedentarity as a primary cause in obesity.

> The fact that exercise causes weight loss has been borne out by numerous controlled experiments. Something I found via a quick search: https://docs.google.com/viewer?url=http%3A%2F%2Fwww.duke.car....

OTOH, exercise makes you hungry. What's more interesting is whether exercise is effective long-term to cure obesity. I'd suspect not alone, but that it certainly helps.

http://www.time.com/time/magazine/article/0,9171,1914974,00....

Who was it that said that if you have $1.5 to spend on food, you're better off (calorically) buying potato chips than broccoli.

High fat/high sugar foods offer the most calories/dollar. So what? If you are fat you have no reason to maximize the number of calories you consume.

Similarly, if you wanted to maximize your salt intake, you can get the most salt per dollar by buying a canister of salt.

It's much better than the popular notion of calories-in/calories-out, though.

Cals in/cals out has been validated in many controlled experiments to be a good first approximation. Taubes' insulin theories have been debunked by experiments.

Incidentally, the standard picture doesn't blame sedentarity as the sole cause of obesity. It blames the combination of sedentarity and increased caloric consumption as the cause.

But the cause, whatever it is, is highly unlikely to be some sort of metabolic disorder. Fat people have a higher metabolic rate than thin people, not a lower one. Their bodies release fat more easily into the bloodstream, contra Taubes and others. They just eat a lot more.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC303803/

http://onlinelibrary.wiley.com/doi/10.1111/j.0954-6820.1969....

http://www.ajcn.org/content/8/5/740.full.pdf

> High fat/high sugar foods offer the most calories/dollar. So what?

Well, the theory is that cheap vegetable oil and sugar causes these metabolic disorders which then causes obesity.

>Taubes' insulin theories have been debunked by experiments.

They're not his theories. He makes the point repeatedly in GCBC that they form part of modern, standard biochemistry. The only controversial points that he makes is that they should be applied to obesity research.

> Taubes' insulin theories have been debunked by experiments.

what are those experiments? My understanding is that carbohydrate-restricted diets generally fare better in terms of weight-loss, muscle-maintenance, and improvements in risk factors of chronic diseases:

http://jama.ama-assn.org/content/297/9/969.full http://www.youtube.com/watch?v=eREuZEdMAVo

Apparently they results are best for people who are insulin resistant, as you might expect.

"PLASMA FREE FATTY ACID TURNOVER RATE IN OBESITY"

I'm not sure exactly what that means, is this referring just to the rate at which FFAs cross fat-cell membranes, or the rate of esterification and lipolysis? Because it's the latter that Taubes argues is primarily important.

Now this is still a controversial topic [5], but my point this kind of explanation seems much stronger and more on-the-mark, than such flaccid ideas like 'americans are getting fat because they don't walk to school anymore'.

I interpreted the article's point is that people avoid any form of physical activity at all cost. One example being driving a child to the end of a driveway instead of letting them walk. If physical activity is essential to maintaining one's health, it seems this sort of decision making would be detrimental to one's health.

I don't see why this is such an awful stance to take.

It's not awful, it just seems off-the-mark. My point is that it seems avoiding physical activity at all costs is better viewed as a consequence of such a metabolic disorder, less so than a cause.

I completely agree that exercise is very important in maintaining health (exercise, especially weight-training is know to increase insulin sensitivity to some degree, for instance), I just think its role in weight-loss, for most people, is greatly exaggerated compared to fixing a diet which actively promotes fat storage (going beyond a caloric excess).

We've been telling overweight people to exercise more and eat less (esp. fat) for 40 years, it simply doesn't' seem to work [1].

[1] http://www.nytimes.com/2012/01/01/magazine/tara-parker-pope-...

Well, the main point of that article seems to be that once someone has been overweight for an extended period of time, it becomes really hard to get to and stay at a lower weight.

So, yes, it suggests that an increase in physical activity isn't an "easy" solution. However, I don't think it affects the point the article is making. People don't wake up to find themselves obese one day. It takes some time and effort to get there. And I would argue one of the biggest impacts on gaining weight is a lack of physical activity.

Not to mention that from my experience, avoiding physical activity has a self-enforcing effect. The more you avoid moving around, the more you want to avoid moving around.

One striking thing to me, as someone who spends half my time in San Francisco and half elsewhere, is how much thinner San Franciscans are than most other Americans. Now, it could be because San Franciscans eat less sugar (perhaps because they are wealthier and eat better on the whole). But the Bay Area in general is pretty wealthy, and I think you still see a lot more large people on the peninsula than in SF. The peninsula is much more car dependent. I don't think it's a coincidence, but I can't prove it either.

I think you probably don't have a good sense of just how much energy walking and other continuous small movements burn. There have several studies that showed that even different amounts of fidgeting can result in significant differences in energy usage, which correlated closely with levels of obesity.

"Overweight people have a tendency to sit, while lean ones have trouble holding still and spend two hours more a day on their feet, pacing around and fidgeting, researchers are reporting in findings published today.

"The difference translates into about 350 calories a day, enough to produce a weight loss of 30 to 40 pounds in one year without trips to the gym - if only heavy people could act more restless, like thin ones."

....

"The director of the study, Dr. James Levine, an endocrinologist and nutritionist at the Mayo Clinic, said the findings offered hope to overweight people, suggesting that relatively simple and painless changes in their daily behavior, like making an effort to walk more and ride less, could help control weight."

Source: http://www.nytimes.com/2005/01/28/health/28weight.html

I picked this one because it's the NY Times and Science, but there are numerous other sources available via Google.

"Overweight people have a tendency to sit, while lean ones have trouble holding still and spend two hours more a day on their feet, pacing around and fidgeting, researchers are reporting in findings published today."

That's exactly what I'm talking about. Most of us eat plentifully. If your metabolism is up to shape, you'll spend the extra calories fidgeting. That's what a lean person is. In this paradigm, a fat person is one who partitions off calories towards fat, regardless of physical activity. He then has to match expenditure to what's left.

Yes.

A number of studies have shown that overweight people can make a difference just by walking around their home a bit more, and doing things in a more active way. For example, instead of sitting down to watch TV they could stand and do some ironing while watching tv. And then, when standing and ironing they can bounce a bit. Many of these seemingly trivial actions build into more exercise and better weight loss.

ridiculous (grandmother driving her daughter essentially to the end of her driveway for the school bus)

I drive my son about half a mile to the school bus every morning. One of my neighbors drives their children from the house, down the driveway to the street to the same school bus.

Their driveway is just under half a mile long!

We're not encouraging laziness: the reason I (and I suspect the neighbor also) do it is because if we just let him walk, he'd screw around and not make it to the bus on time. Eleven year-olds do stuff like that.

He walks home from the bus because it doesn't matter if it takes him a few extra minutes to get home.

Exactly. The organized sports for kids is insane in its breadth and depth. We used to play one, maybe two sports. Now normal kids are playing something most seasons. Not only are they playing, but they are going to special coaching sessions, camps, and so on. This is much more prevalent today than when I was a kid.

We had football practice twice a week (at 12 yo) with a game on Saturday.

She got a ride to the end of the driveway? Probably because she has a double-header soccer match that night. A soccer match at which some parents will get into a fistfight- but that's for another thread.

She got a ride to the end of the driveway? Probably because she has a double-header soccer match that night.

Someone athletic enough to play in a double-header soccer match wouldn't bat an eye at walking 100 feet down a driveway. As someone who played many sports in my earlier years, this line of reasoning seems completely off the mark.

I see it, though. Not quite to that exaggerated level, but not entirely hyperbolic either. It's not a matter of "they cant't do it," but "they don't have to do it." Not if an alternative is offered (and they like being with grandma anyway).

I see people who drive to the gym. They park their cars as close as possible to the gym door. This is not in poor weather.

(not making any comment about the article.)

My point is that I'm not convinced that the kids are getting less exercise than previous generations. If I had to guess, I would guess they are getting more. Are they watching more TV? You bet. What they don't spend time on so much anymore are hobbies. Sports are the main hobbies of a lot of these kids.

Not for every kid, to be sure. But for a helluva lot of them.