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Low carb vs. low fat...again

Posted by Dr. Suzanne Koven  July 3, 2012 08:42 AM

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low-carb-vs-low-fat again-640x408.jpgHave you been following the latest in the ongoing controversy about whether a low carb diet is healthier and better for weight loss than a diet low in fat?

If you lived in the 19th century you would have.

The question of whether it matters what we eat--not only how much we eat--has been hotly contested for well over a hundred years.

A study released last week in JAMA and summarized here reports that overweight and obese young people who lost weight on a reduced calorie typical American diet and then ate a low fat diet were at greater risk of regaining the weight due to slowed metabolism than those who consumed the same amount of calories via a low carbohydrate diet. Those who ate more refined carbs were more likely to have insulin resistance and risk of diabetes.

The results imply that the calories in a "100 calorie pack" of cookies do not affect the body in the same way as, say, 100 calories of apples or fish or beans.

This new study, conducted at Boston Children's Hospital and Brigham and Women's Hospital, joins a very long debate about the ideal composition of our diets.

In the 19th century, two major nutritional gurus held diametrically opposed views.

William Banting, an English undertaker who lost weight by limiting bread, beer, and other starchy foods, espoused what we now call a low carb diet. His approach, endorsed by highly respected physicians including Sir William Osler (considered the father of modern medicine), was so popular that, for a time, "dieting" was called "banting."

The opposing point of view was held by New Jersey minister Sylvester Graham--yes, the inventor of Graham crackers--who encouraged a diet high in grains, fruits, and vegetables with little or, preferably no meat. He heavily influenced Dr. John Harvey Kellogg (yes, that Kellogg), who ran a sanitarium in Battle Creek, Michigan. Kellogg treated his patients with Graham's high carbohydrate regimen, including Kellogg's Corn Flakes--which he invented.

Throughout the 20th century, especially as the obesity rates rose, the merits of a low carb diet were touted most famously by Dr. Robert Atkins, and the low fat diet most famously by Dr. Dean Ornish.

A 2009 study in the New England Journal of Medicine seemed to end the decades-old argument definitively: when researchers compared low fat, low carb, and Mediterranean (emphasizing whole grains, lean proteins, fruits, vegetables and "healthy fats" such as nuts and olive oil) diets--there was no clear winner for weight loss--though the Mediterranean diet may have had an edge.

The new study from Children's and Brigham and Women's reopens the debate, but by no means settles it in favor of the low-carb camp. The study was small (22 subjects) and the period in which the dieters were assessed for risk of regaining weight was short (4 weeks).

So what do I tell my own patients about the low carb vs. low fat question?

It seems pretty clear that the rise in obesity in the U.S. has coincided with the rise in consumption of processed foods of all types--600 extra calories a day compared with 40 years ago by one estimate--and more sedentary lifestyles.

If you are over 50, you only have to recall your own childhood to realize that when people ate much smaller portions, less sugar and fat and sat around looking at screens or driving for fewer hours a day--the average adult wasn't obese.

I'm also impressed that my own patients' experience mirrors the data from the National Weight Control Registry, which tracks people who have lost weight and maintained that weight loss: no one particular diet is magic.

I've had patients who have done well with Weight Watchers, South Beach, and--most commonly--balanced diets they've devised for themselves; usually by some combination of measuring portions or counting calories, and eating less processed, takeout, and restaurant food--plus regular exercise.

Bottom line: successful losers eat less, move more and, yeah, they eat fewer cookies than apples--which Banting and Kellogg would likely both have supported.

This blog is not written or edited by or the Boston Globe.
The author is solely responsible for the content.

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About the author

Suzanne Koven, M.D. practices internal medicine at Massachusetts General Hospital in Boston. She writes a monthly column for the Globe's G Health section and her essays have appeared in the More »


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