Monday, January 30, 2006

Atkins, Ornish, Weight Watchers & Zone Study - a Waste of Time

A study was published in JAMA - Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction - a couple of weeks ago, before I was in major "conference prep mode" that I wanted to write about. It was published around the same time as the study - Low-Fat Dietary Pattern and Weight Change Over 7 Years - that I've previously written about. Interestingly, this comparison study received little, if any, media attention.

Now that the 2006 NMS Scientific Sessions are complete and I've had a mini-vacation to relax a bit, it's time to get back to the business of analyzing some research!

As I read through the study data, something interesting popped out - none of the participants, in seems, were able to actually follow the rules of the diet they were assigned to follow. That tidbit, in and of itself, is another article.

For now, I'd like to concentrate on something much more intriguing that comes to light when you look at the actual calorie intakes and compare that to the weight loss numbers.

The first clue that something is "just not right" is found it what is not said - there is no statement or acknowledgement that the weight loss experienced by participants is accounted for by the calorie restriction each diet imposed.

Why? Let's find out...

This study was over a period of one year and there were some extreme calorie fluctuations thorughout. Each group was assessed at "baseline" and then at 1-month, 2-months, 6-months and one-year. The findings provide the first insight into just how extreme the calorie swings and creeps were in each diet:

So, what's wrong with this picture?

Well, first of all it's highly unlikely that a group of 200+ pound people are consuming just around 2000-calories a day at baseline and sport a BMI of 35 on average! So, that's our first clue that the study has what is called a "reporting bias" caused by those participating under-reporting their actual food intake at the start of the study.

But, let's pretend that is really all they were eating, OK?

Now look at just how significantly calories were restricted on some of the diets. The folks in the Zone managed to reduce calorie intake over the first month by 642-calories a day, then in month two they managed to keep calories reduced by 625-calories a day below their baseline start calorie intake, followed by an average of 173-calories less a day in months 3-4-5-and-6 and an astounding 302-calories fewer over the last six months.

So, where's the 32-pound weight loss expected with such a calorie restriction? Why did these folks manage just 7.04-pounds of weight loss? Was this just a phenomenon of those in the Zone?

Not exactly. In fact, all groups had calorie restrictions that should have resulted in greater weight loss. The calorie restriction of the Ornish group should have resulted in 23.76-pounds of weight lost, in the Weight Watchers group a weight loss of 30.78-pounds should have been realized and in the Atkins group, the expected weight loss should have been 5.4-pounds.


Hold on a second.

The Atkins group, even though they were obviously not really following a "low-carb" diet, should have had a predictable weight loss of 5.4-pounds and lost 4.6-pounds? That's mighty close to the expected weight loss, especially when we compare how poorly the other groups did when compared with their calorie restriction!

What prevented the other groups from not losing the weight they should have based on the Calorie Theory (calories in versus calories out)?

Call me crazy, but 1300, 1400, heck even 1600-calories a day is simply too few calories for someone weighing an average of 220-pounds with an average BMI of 35. After reviewing the amount of carbohydrate consumed by those supposedly following Atkins, I'm not surprised they lost just 4.6-pounds in a year - they were eating too many carbs to effectively burn body fat!

But, they were eating more calories each day - enough to support weight loss without throwing their metabolism into "starvation mode" where the body thinks it is in a famine and really conserves energy rather than burn it. I would wager that if they'd actually followed Atkins - actually kept their carbohydrate intake at levels recommended by Atkins - they would have seen some impressive weight loss! Too bad the researchers didn't make sure each group actually was following the plan assigned during the first two months where support and intensive education was part of the design protocol.

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