Most people who exercise won't lose much, if any weight without calorie restriction. And most people who try to restrict their calories below what their body wants fail over the long term--eventually, their appetite wins.
McArdle links to a book written by a journalist, not a scientist, with a very debatable premise--being overweight does not affect health adversely and obesity is determined by genetics, so overweight people can't lose weight because their bodies will be overwhelmed by the desire to eat more if they try to cut back on the amount they eat. Why does McArdle, who equates fat with the lower classes and therefore self-indulgence, show this unusual sympathy? Let's ask Mark Ambinder, who responded in 2009 to one of her post on obesity.
McArdle approaches obesity as if it were a Foucauldian construct: a category invented by the government to justify an exercise of power. The government has no business intervening on the level of individual choice and it shouldn't get into the business of behavioral suasion because it always fails. She's right to note that information about health risks associated with overconsuming fat and sugar and salt are saturated throughout society, even supersaturated. Everyone knows how bad this stuff can be. For her, that's the end of the argument. Government can help to provide information about how to make better choices, but it cannot and should not try to persuade people to make better choices. Indeed, the push for people to make better choices produces the stigma that makes the bad thing bad in the first place.
This assumes that the stigma itself is misplaced. It isn't. Fat stigma is bad and harmful, and it ought to be reduced. But reducing fat stigma doesn't reduce the incidence of obesity; it actually seems to increase it in certain populations. What produces fat stigma is not a government or culture that hectors people to lose weight and exercise and then excoriates them when they can't; it's a government that expects individuals to lose weight on their own (which is next to impossible) while making policy that keeps people fat. The discrepancy between expectations and reality is cruel, especially for children.
Lo and behold, government policy has helped ensure that the raw foodstuffs that go into all the starchy, sugary foods that we eat are much cheaper. And when compared to the consumer price index, fruits, vegetables and healthy foods are more expensive than they were 30 years ago. If government policy influences diet on a macro scale, and if there is evidence that the diet is harmful, then, in theory, there would be no additional intervention if, say, Congress began to subsidize tomatoes in the same way it subsidizes corn, just a change in policy.
None of this argues for a soda tax, or a tax on sugar, or a ban on, say, food marketing to children. It's just to say that if the obesity epidemic was nurtured by policy -- and it clearly was -- perhaps it can be undone by policy, too.
But McArdle read a couple of books that prove her anti-government fantasies are correct!
Fat tissue makes people want to eat--it sends out for takeout. And hunger is a signal on par with thirst or pain. You can ignore it, if you have sufficient willpower. But just as most people can't withstand torture (a minority can), most people can't ignore the constant demand from their body for food.
The other is that while I do buy some of the arguments about hyperpalatable food like Doritos (though I personally find Doritos eminently resistable [sic] most of the time), the fact that a really attractive food combination has been cooked up by food scientists does not mean that you get some kind of free pass to deny it to everyone. Whether a dish was dreamed up by Mario Batali or the staff at the Cheesecake Factory, preventing people from having it "for their own good" still represents an actual hedonic loss, as well as an actual loss of freedom. You may think they have some meta-self which will thank you later, but their current self has still had both its liberty and its joy restricted. Invoking the demon food scientists of agribusiness does not actually relieve you of the obligation to prove that intervening in the liberty of both the customers and the company is morally pressing.
To be sure, even I, the pessimistic libertarian, do not see any actual means for the government to prevent food processors from making their food taste very good. (Thank God). I just suspect that more than one of my interlocutors is casting around for just such a means.
The government could raise the price of fat, salt, and sweeteners, processed food, and restaurant meals. But I very much doubt that if our legislators actually enacted a food tax adequate to prevent obesity, they would get much thanks from anyone except the sort of people who ask each other, with wide eyes, if anyone else has noticed how disgustingly fat all the people are at the mall--and never eat at Cheesecake Factory. So I think that this, too, is unlikely.
Ultimately, the answer to "what could it hurt"? is that all actions have costs, which you cannot assume away on the grounds that those costs don't interest you. But they should interest you, because not least among those costs is the simple fact that the government cannot do everything well. Making all sorts of changes in the name of obesity means not making others that might be more important, because we have limited political and bureaucratic bandwith. [sic] Do you want obesity intervention, cap and trade, or health care reform? You may not be able to have any of them. But you probably can't have all three. And if you did, you'd make it more likely that the government would screw all of them up.
And I suppose I would make the point that at the margin expenditures of funds to fight this tendency are going to do a lot more to improve public health than will expenditures of funds to treat people's diabetes.
That presumes you can find a marginal dollar that will reduce peoples' tendency to eat more than they burn just as effectively as we treat diabetes. Seven years ago, when I investigated fast food lawsuits, I found very little evidence for that proposition. Pretty much every public health effort to get people to eat less has proven a dismal failure. As Paul Campos has noted, telling people to eat less and exercise more is the most exhausitvely [sic] attempted experiment in the history of science. And we have 200 million data points that prove just how badly it works at keeping Americans slender.
I'm thus pretty skeptical that we're going to do much about obesity through the sort of mild nudges that a lot of the discussion about changing peoples' eating habits implicitly imagines. For example, I'm a big fan of Brian Wansink's Mindless Eating, which details all the ways that we take in more calories than we think. But I'm skeptical that in the long run, these factors make all that much difference. If you think about it, taking in an extra fifty calories a day more than you need--half a piece of bread, or a few cocktail nuts--is enough to pack on an extra five pounds a year. If we really at that mindlessly all the time, we'd all be morbidly obese. I expect that in any given sitting, things like portion size, or calorie counts, can cause people to reduce their intake. But over time, I doubt they'll have much impact.
That leaves more illiberal options, like forcing manufacturers to change their foods in order to make them less apealling, [sic] or massive taxes on fat, sugar, and salt. Even if I thought there was a practical, and politically acceptable, way to carry this out, I'd be against it. Enacting national health care, and then declaring that it now gives you the right to dictate how people will eat . . . well, that's exactly the sort of thing libertarians are talking about when they bemoan the creepign [sic] nanny state.
McArdle has grown more canny over the years and now declares that we must ignore corporate-friendly agriculture policies that adversely affect our national health because of freedom and puppies and it's-for-the-children. But it all comes down to the same thing--the lower class is fat because of genetics and nothing can be done about it, so leave McDonalds alone.