Immunity and obesity

Really interesting article from James Hamblin looking at the latest research on the complicated interplay between your immune system, you digestive system, and your weight.  Short version: it’s so much more complicated than we realized:

Instead, it is becoming clear that some people’s guts are simply more efficient than others’ at extracting calories from food. When two people eat the same 3,000-calorie pizza, for example, their bodies absorb different amounts of energy. And those calorie-converting abilities can change over a person’s lifetime with age and other variables. [emphasis mine]

The question is, why? And is it possible to make changes, if a person wanted to?

If so, the solution will involve the trillions of microbes in our intestines and how they work in concert with another variable that’s just beginning to get attention. The immune system determines levels of inflammation in the gut that are constantly shaping the way we digest food—how many calories get absorbed, and how many nutrients simply pass through…

This is the interesting part to Steven Lindemann, a researcher at Purdue University who was not involved in the Utah study. He studies the effects of foods on the gut microbiome. “Although we know that, on the balance, diet is the strongest contributor to gut microbiome composition,” he said, this study suggests that when immune control of the colon breaks down, growth can become unchecked and cause problems with metabolic regulation.

Lindemann says the fact that the immune system regulates the inhabitants of the small intestine is well established. He compares the bowel wall to a customs checkpoint: The goal is to weed out bad actors and illegal cargo, but allow legitimate trade to progress as rapidly as possible. In the case of the immune-altered mice, he says, “we have a colonic border patrol that is seemingly out to lunch, allowing bad actor Desulfovibrio to bloom.”

If similar microbial changes have comparable effects in humans, it could have far-reaching implications for our diets. The very ideas of “nutritional value” and “calorie content” of food seem to vary based on the microbial population of the person eating it and, potentially, her immune status. A person’s own microbes—and those contained in any given food—would have to be considered as another ­component of the already flimsy calories-in, calories-out equation. This would also compound the challenges already facing nutrition labels

Stephens says the relationship between weight and the immune system is likely to get more complicated before it gets simpler. That makes it difficult to give concrete advice. “Keeping diverse gut microbes with diverse dietary sources is probably the safest advice for now,” he says. “That will stimulate a healthy, strong immune system that can learn and regulate and do all the things it does, in ways we’re just beginning to understand.”

If all this uncertainty makes nutrition guidelines and nutrition even more inscrutable, it also stands to do some good by undermining the moralizing and simplistic character judgments often associated with body weight. Seeing obesity as a manifestation of the interplay between many systems—genetic, microbial, environmental—invites the understanding that human physiology has changed along with our relationship to the species in and around us. As these new scientific models unfold, they impugn the idea of weight as an individual character flaw, revealing it for the self-destructive myth it has always been.

Damn, we still have so much to learn about how our bodies work.  Especially when we look at the incredibly complex interplay between our bodies and the species (mostly bacteria) that we live with.  That said, when it comes to diet and weight, I think, “eat food, mostly plants, not too much” still sounds like a pretty good heuristic.

It’s really pretty simple

This from David Frum is great:

There is one developed country—and only one—in which it is not only legal, but easy and convenient, to amass a private arsenal of mass slaughter. That country also happens to be the one—and the only one—regularly afflicted by mass slaughters perpetrated by aggrieved individuals.

You would not think that this is a complicated problem to puzzle out. Yet even as the casualties from gunfire mount, Americans express befuddlement, and compete to devise ever more far-fetched answers…

America’s uniquely bloodstained record of violence is a consequence of America’s uniquely reckless attitudes toward weapons of mass death.

More guns, more killing. Fewer guns, less killing. Everybody else has figured that out. Americans—and only Americans—refuse to do so.

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