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Review of the diet research

As promissed, here is my little review of the reseach which has been all over the news regarding the Atkins diet and how it stacked up to three other diets in testing. If you need to look at the news article, I posted it in my last blog entry which was made 2 or 3 days ago.

Gardner CD et. al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007 Mar 7;297(9):969-77.

Like I mentioned in my previous entry, I had a lot of questions about this study and how it was conducted. I had these questions for 2 reasons:

a) I am incredibly anal and I want to see things with my own eyes before I make a conclusion.


b) The media usually does a piss poor job of interpreting research and informing the public.

So, with a critical eye, I read through the study.

First the facts:

The study set out to compare four different diets. The Atkins diet (a low carbohydrate diet), The Zone Diet (a diet which consists of 40% carb, 30% protein and 30% fat), the Learn Diet (short for Lifestyle, exercise, attitudes, relationships and nutrition. Basically a low fat diet which is centered around national nutrition guidelines....ie, the food pyramid) and the Ornish diet (which is a very low fat/high carb diet).

The subjects were pre-menopausal women, aged 25-50, with body mass indexes of 27-40 (so basically they ranged from being overweight to obese). There were various factors which excluded certian women from the study (which I wont go into).

The study lasted for 12 months, with data being collected at months 2, 6 and 12. So start, half way and finish. The women were given books and classes, led by a registered dietician, one hour per week for 8 weeks on how to manage their particular diet.

The participants were to self report their food intake and physical activity. Subjects were tested in weight loss, body fat, blood pressure and blood samples looking at cholesterol and blood glucose.

The results were this:

Aktins- 4.7kg (10.34lbs)
LEARN- 2.6kg (5.72lbs)
Ornish- 2.2kg (4.84lbs)
Zone- 1.6kg (3.52lbs)

Whoop-dee-do!! The best they could do was 10lbs in one year? Would anyone be excited about that kind of weight loss? Maybe 10lbs in 10 weeks, right? Come on! Also, if anyone has done a low carbohydrate or keto-genic diet, you certaily know that it is very easy to lose 5-8lbs of weight (water) in the first 5 days. Does that make these results very significant? Not in my opinion!

Lets look at the last couple of sentences in the results section:

"The pattern of changes in body mass index, percentage of body fat, and waist-hip ratio among groups parallel the changes in weight, although the between-group differences at 12-months did not achieve statistical significance for percentage of body fat or waist to hip ratio."

hmm...The changes in body fat percentage weren't significant. I wonder what their activity levels looked like? Did these people train? Maybe if they had a set exercise program over the 12-month period the results would have been different. Would the Aktins group have lost more weight, given that they were intaking less carbohydrate and possibly not able to exercise at a higher work rate than say the Zone group? Who knows. Maybe in another study they will look at this.

Also, as with many studies relying on self-reporting things tend to go out the window. People are very bad at reporting both their caloric intake and energy expenditure and typically over-estimate what the expend and under-estimate what they take in. They study says that over the 12 month period the participants were lowering their calories (everyone was supposed to be intaking the same amount of calories), but the groups started to gain back weight?? Are we really to believe that those people were properly estimating their intake/expenditure given a statment like that? If you are continually taking in less, should you not be losing more? They just started to gain weight back? That doesn't make much sense, does it?

I don't feel that this study shows us very much. I still contend that a well-balanced diet with proper exercise prescription will leave you with the best results. The Atkins diet may be satisfying to people because of the water lossed so quickly (it gives them a sense of accomplishment), which is great! However, once the novelty wears off, can you really stick with that type of diet for an extended period of time? The whole goal is to never have to diet, rather to live healthy. Eating the atkins diet doesn't teach you much in the way of how to eat and maintain a healthy lifestyle. Also, as I stated previously, if you are going to engage in any type of vigorous exercise, the lack of carbohydrates is really going to leave you in a rut after awhile.

Just find a healthy balance!