Whose fault is it if you're fat? More precisely, if you carry more fat than is considered healthy, is it just because you lack willpower around food?

Three new studies deliver three more blows against the argument (and implied shame game): "If you're fat, it's because you eat too much, and you only have yourself to blame."

Here's a round-up of the reports:

Study #1: Researchers at the Emory University School of Medicine have discovered that disruptions to normal, healthy gut bacteria can make you pack on the pounds. Their study-which looked at mice, not humans-found that when the "wrong" kind of bacteria takes over the gut, there is a systemic increase in inflammation, decrease in insulin resistance, increase in appetite, and tendency to gain weight. The scientists suggest that heavy antibiotic use and other environmental factors could be playing a role in many cases of obesity by changing what's happening in our guts.

Sure, the mice who gained weight were eating more. But if your appetite suddenly increased, how easy would it be for you to keep your food intake the same? This study points to the challenge of living in a world that can profoundly interfere with the body's ability to regulate hunger and fullness.

Study #2: Another depressing finding about the perils of sleep deprivation (unless you're looking for another good reason to sleep in - in which case, enjoy). Adults under age forty who get less than five hours of sleep a night have higher concentrations of visceral fat. This type of fat, which wraps itself around internal organs, is much worse for your health than a double chin or cellulite on your thighs.

Other studies have shown that sleep deprivation disrupts everything from blood sugar control to food cravings. In this study, black women and Hispanic men were the most likely to get less than five hours of sleep per night. The researchers wonder whether these sleep trends (and not diet alone) help explain the rising obesity rates among black and Hispanic populations.

Study #3: The last report is not a single study, but an excellent write-up in the New York Times about how a desk-job leads to weight gain (and dying sooner). This article by Olivia Judson details several recent studies showing how the body shuts down when you sit down. Sit at a desk all day, or watch three hours of TV at night, and it doesn't even matter if you squeeze in an hour of exercise. A full hour! Every day! It's not enough to counter the metabolic disaster of being sedentary the rest of the day. That's right, even people trying to do the right thing have the deck stacked against them.

These reports are each interesting on their own. But a curious curator of science may wonder: Why the recent surge in fat studies that have little to do with diet?

A cynic might say this research trend-and our fascination with it-reflects the nation's deep desire to avoid taking personal responsibility for weight gain. And maybe we do have our heads in the sand when it comes to what kind of serious behavior change our nation requires. After all, another report in the New York Times this week summarizes research showing that modest calorie restriction has no effect on weight. Much more drastic change is required, the kind that makes many people say, "I'd rather be fat."

I prefer to think that researchers are catching on to the complexity of the obesity problem. In the last decade, the conversation has shifted somewhat productively from "blame it all on the fat people" to "blame it all on McDonald's." In the coming decade, we'll keep discovering there's no one thing to blame, and no simple solution. And in the meantime, we'd all do well to keep in check oversimplified explanations about why we (as a nation) are getting fatter, and overoptimistic advice about what to do about it.

Feel differently? Share your theories in the discussion. And for those interested in addressing health without dieting, may I point you toward the Health At Every Size approach (http://www.sizediversityandhealth.org/). Looking for big policy solutions that go beyond putting every American on a diet? Check out Stuffed Nation (http://www.stuffednation.com/stuffednation-obesity-epidemic.htm).

Studies Cited:

1. Vijay-Kumar M, Aitken JD, Carvalho FA, et al. Metabolic Syndrome and Altered Gut Microbiota in Mice Lacking Toll-Like Receptor 5. Science, published online March 4 2010.

2. Hairston KG, Bryer-Ash M, Norris JM, Haffner S, Bowden DW, Wagenknecht LE. Sleep Duration and Five-Year Abdominal Fat Accumulation in a Minority Cohort: The IRAS Family Study. Sleep, 2010; 33(3): 289-295.

3. Judson, O. Stand Up While You Read This! The New York Times online. February 23, 2010. http://opinionator.blogs.nytimes.com/2010/02/23/stand-up-while-you-read-...

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