I have yet to see any installments of the long-running Fast and Furious movie franchise, although my son and I recently agreed we probably should. There is, however, a much longer franchise that Ive been watching closely throughout my career: the fad and folly franchise, devoted not to fast cars, but fast weight loss and promises of high-octane health, achieved magically and without effort.

There is a new one on the marquee at the moment. I put new in quotes for two good reasons. First, we have known there is no truly new thing under the sun since Ecclesiastes. Second, that is more true of weight loss than anything else. Standard operating procedure in the weight loss space is to wait out the 20-minute attention span of our culture, and then re-peddle repackaged leftovers as new.

Given that, the new item here is fasting. Fasting, of course, is the furthest thing from new. When actual scholars write about the Paleo diet, the intermittent cycles of feast and famine that figure in the catch-as-catch-can diets of hunter/foragers get prominent mention. Intermittent fasting has almost certainly, almost always been part of the human dietary experience for want of choice.

Eventually, of course, it did evolve into choices such as those made by most major religions to impose times of fasting. Whether this was about public health, crowd control, spiritual concentration, or strategic rationing, I defer to historians, sociologists, and theologians. We may simply acknowledge that among the many non-new things under the sun, fasting is notable.

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But there is a new study about it, and that has engendered a constellation of media attention, in which my own recent interviews have figured. The study assigned a group of overweight people to either their usual diet, or fasting five days per month for three months. Those who fasted lost weight.

What is being touted as new is improvement in an array of metabolic markers, spanning lipids, glucose, and measures of inflammation, in the fasting group. The study authors suggest this is a benefit of fasting, and the media have seemed fairly inclined to eat it up. If you are sensing I dont buy it, you are correct.

Short-term weight loss among those with an excess of body fat improves metabolic markers temporarily at least no matter how its achieved. Cholera works. So does cocaine. That does not make either of these a good idea.

Playing to the popular palate, coverage of the fasting trial implies something uniquely, even magically beneficial about fasting. But as I see it, all weve got is this: eating some of the time leads to weight loss relative to eating all of the time. Weight loss, in turn, produces short-term improvement in all of the biomarkers that weight loss always improves, whatever good or bad, sustainable or fleeting thing is causing the weight loss. Fasting has not been shown to have anything that cabbage soup, or grapefruit didnt have before.

Is intermittent fasting a good idea? I think I can be. If the fasting is suitably intermittent, sustained over time, and combined with sensible eating the rest of the time it can be beneficial. That said, if it does temporarily and then stopped; or associated with eating poorly on bingeing on the other days I think it can just as readily be harmful. Its certainly no panacea.

Of course, when fasting is being peddled to us, we are unlikely to get any such provisos. The Fast Diet, for instance, makes all the customary promises. The assertions that invariably accompany diet claims always make me think of Bertrand Russell: The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. I think Bert should included swindlers on his list, but otherwise pretty much nailed it.

Until or unless my son and I indulge in that movie marathon weve discussed, I wont really know where those guys are going fast, or why they are furious. I do know, however, that public health nutrition has been going nowhere fast for decades, spinning our wheels instead in the repetition of folly. I do know that we should all be furious about a culture propagating obesity and chronic disease for profit with willfully addictive junk food.

And alas, I also know that misplaced hope will likely triumph over experience yet again, and the public will line up to buy tickets to the latest installment of fast-weight-loss-meets-false promises, never noticing that fools, fanatics or swindlers are in the drivers seat just about every time.

Dr. David L. Katz;www.davidkatzmd.com; founder, True Health Initiative

Excerpt from:

Dr. David Katz: Preventive Medicine: The fasting and the furious - New Haven Register