Tuesday, June 17, 2008

More A to Z Diet Trial Data

Readers may recall that last year, in March 2007, a study was published from a dietary trial comparing four dietary approaches for weight loss: Atkins, Ornish, LEARN and Zone - the A to Z Weight Loss Study.

Many reading through the findings cried foul - those in the Ornish group hadn't reduced their fat sufficiently, those in the Atkins group consumed more carbohydrate than recommended, and so on.

In my blog post I noted "...this study failed to achieve compliance out of the gate!"

I also noted that "We have before us is a study that really does indicate carbohydrate restriction can work well over a period of one year. Without sub-group analysis to evaluate results tied to compliance (hey, some of the participants had to be doing the various diet right, dontcha think?) we can't know just how effective doing Atkins or any of the diets is with good compliance though since the researchers didn't take their data to that level of analysis in this paper."

Ask and ye shall have an answer!

A follow-up paper was published in the International Journal of Obesity - Dietary Adherance and Weight Loss Success Among Overweight Women: Results from A to Z Weight Loss Study.

As the researchers note in the background of their abstract: "Dietary adherence has been implicated as an important factor in the success of dieting strategies; however, studies assessing and investigating its association with weight loss success are scarce."

Their objective?

"We aimed to document the level of dietary adherence using measured diet data and to examine its association with weight loss success."

And so they performed a secondary analysis on the data from the trial and lo' and behold, those who closely adhered to the dietary recommendations of their assigned diets were found to have greater weight loss when compared with those less compliant with their dietary recommendations.

The researchers found that "within each diet group, adherence to score was significantly correlated with 12-month weight change."

Atkins rs= 0.42 p=0.0003
Zone rs= 0.34 p=0.009
Ornish rs= 0.38 p=0.004

When comparing the highest level of compliance with the lowest the researchers noted significant differences in weight loss in the Atkins group!

Highest compliance = 8.3kg
Lowest compliance = 1.9kg
p = 0.0006

Highest compliance = 3.7kg
Lowest compliance = 0.4kg
p = 0.12

Highest compliance = 6.5kg
Lowest compliance = 1.7kg
p = 0.06

The researchers concluded, "Regardless of assigned diet groups, 12-month weight change was greater in the most adherent compared to the least adherent tertiles. These results suggest that strategies to increase adherence may deserve more emphasis than the specific macronutrient composition of the weight loss diet itself in supporting successful weight loss."


  1. Chris1:26 PM

    More than 18 pounds in a year for the people doing Atkins better isn't shabby!

  2. Losing weight by following any on the diets is possible. The hard part is to stay on the diet the rest of your life to avoid regaining the weight. I cannot envision that many people could stay on Ornish for more than a few months.

    I've been on Atkins for over 5 years and have little problem sticking on it.

  3. Anonymous2:33 PM

    Did they say what proportion were compliant for each group?


  4. Did they say what proportion were compliant for each group?

    I don't have full access to the journal it was published, so I didn't pay for the full-text - the above results were what the abstract shared. If I do get a copy of the full-text, I'll write more about the findings!

  5. These results suggest that strategies to increase adherence may deserve more emphasis than the specific macronutrient composition of the weight loss diet itself in supporting successful weight loss."

    Yes, and monkeys might fly out of my butt. Seriously, wasn't one of the prominent features of this study the fact that the Atkins dieters had better lab numbers than either of the other two groups? Is weight loss our only goal here or do the numbers matter as well? I would think it'd be the latter. OK then, so macronutrient composition DOES matter. Why do these people so resolutely refuse to see the evidence?

  6. Anonymous10:26 AM


    Here is what they said about the numbers in each group who were compliant to the diets.

    "Across all three diet groups, only one participant, in the Ornish group, met the criteria for absolute adherence at all three post-randomization time points. A total of nine participants from the three diet groups met the absolute adherence criteria for at least two of the three post-randomization time points (Atkins, n=6; Ornish, n=1; and Zone, n=2)."

    "...dietary data were available at all four time points for 181 women (78%) (Atkins, n=68; Zone, n=57; and Ornish, n=56)."

    So, 6 out of 68 women in the Atkins group were adherent (8.8%); 1 out of 56 in the Ornish group (1.8%), and 2 out of 57 in the Zone group (3.5%).

    But they don't give any other data comparing absolutely adherent vs non-adherent participants. Instead they divide the participants into tertiles.

    "Further analyses were based on relative adherence (tertiles)."

    Most adherent (tertile 1) and least adherent (tertile 3).

    They do not give numbers of participants in each tertile, or what the cut-off's were for each tertile.

  7. I so, so, so WISH that just ONE study that is tracking/comparing weight loss would actually bother doing a body fat water testing instead of just pounds on a scale.

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