Marc Ambinder has some interesting pieces up at the Atlantic on the First Lady’s efforts to combat childhood obesity. I obviously have a lot to say on that but am short on time. In the mean time I will point you to Robert Lustig’s Nature article on childhood obesity, which was a watershed for me personally.
The article is a bit dense for those without a science background, nonetheless, it is extremely valuable. I recommend opening Lustig in one window and Wikipedia in another and just making the hard slog.
Here is the abstract
Childhood obesity has become epidemic over the past 30 years. The First Law of Thermodynamics is routinely interpreted to imply that weight gain is secondary to increased caloric intake and/or decreased energy expenditure, two behaviors that have been documented during this interval; nonetheless, lifestyle interventions are notoriously ineffective at promoting weight loss. Obesity is characterized by hyperinsulinemia. Although hyperinsulinemia is usually thought to be secondary to obesity, it can instead be primary, due to autonomic dysfunction. Obesity is also a state of leptin resistance, in which defective leptin signal transduction promotes excess energy intake, to maintain normal energy expenditure. Insulin and leptin share a common central signaling pathway, and it seems that insulin functions as an endogenous leptin antagonist. Suppressing insulin ameliorates leptin resistance, with ensuing reduction of caloric intake, increased spontaneous activity, and improved quality of life. Hyperinsulinemia also interferes with dopamine clearance in the ventral tegmental area and nucleus accumbens, promoting increased food reward. Accordingly, the First Law of Thermodynamics can be reinterpreted, such that the behaviors of increased caloric intake and decreased energy expenditure are secondary to obligate weight gain. This weight gain is driven by the hyperinsulinemic state, through three mechanisms: energy partitioning into adipose tissue; interference with leptin signal transduction; and interference with extinction of the hedonic response to food.
Emphasis mine
I don’t agree with all of Lustig’s conclusions as written in the article. This is in part because the accurate answer to some of the questions is: “I really have no idea and neither does anyone else.” Yet, that’s hard to get published.
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Wednesday ~ February 10th, 2010 at 2:22 pm
TGGP
Maybe the science is good (I’m no expert), but some of the passages are weird.
The concept of personal responsibility is, however, not tenable in children
Isn’t that a bit extreme? We may have different standards for children, but most everyone accepts that the concept of personal responsibility applies to them. His note about the social ramifications of obesity would also I think apply to adults. It seems to me that he’s using a “Think of the poor children!” semantic stopsign.
Just last night I was in a discussion on the role of insulin in hunger. I had heard that people in eating competitions drink some soda shortly before to stimulate insulin production (and hence, hunger) after abstaining from food for a while. The Nature article suggests I was misinformed.
I had never heard of hypothalmic obesity. That’s interesting.
I am puzzled what “forced weight loss” means? Did they just lock people in a room without much food? And if that worked why did they earlier observe the “plateau” due to the starvation response after initial weight loss?
They mentioned elevated risk among African-Americans, but I had just read an uncredentialed blog commenter claim that it is only among females rather than males* (which would seem to undercut neighborhood-based explanations). Being unable to remember where the comment was, I resort to Google and PubMed. Lustig writes that puberty and pregnancy are both periods of hormone-driven weight increase. So his theory would seem to jibe better with that gender disparity, and it would have only helped him to note it.
*I recall Tim Harford giving a gender-ratio argument for why black females have higher education rates than males (and also why marriage rates are low). I would assume that obesity is at least as harmful in the marriage market as low education, and may even be harmful in gaining employment (though to a lesser degree and possibly in violation of discrimination law). You may have read the NYT article on how the gender ratio at colleges allows men to act like slobs, pigs or cads. It would have similarly led one to expect that women would all be toning their abs while men indulged their guts. Lustig’s theory that it is very hardwired rather than amenable to incentives (obesity is surely stigmatized) helps to explain why things are not according to expectation.
Wednesday ~ February 10th, 2010 at 2:55 pm
Karl Smith
No doubt Lustig is a bleeding heart and his statements on children are extreme. The more sensible version is this:
We have large degree of control over the incentives that children face. We can essentially deprive them of “bad foods” and all but force them to exercise. Yet, even under these great pressures the children fail to keep weight off long term. This suggests that there is some equally strong endogenous mechanism pushing in the opposite direction. That mechanism seems to be related to the hormones, insulin and leptin among others.
Indeed, I think more recent research has suggested the field of hormones playing a role in weight regulation is huge. The two most important hormones to recently gain fame are grehlin and peptide YY.
Monday ~ February 15th, 2010 at 9:40 pm
Rethinking physics « Entitled to an Opinion
[...] that? Lustig hypothesizes that in puberty & pregnancy such an effect is desirable. Hat-tip to Modeled Behavior, who probably linked the study before without my bothering to read [...]