Weight loss books are plentiful and fad diets are ubiquitous, with many giving guidelines on and being structured around different combinations of macronutrients, but with little concern to micronutrients. A weight loss diet does not equate to a health-promoting one (similarly, a diet with healthier foods does not equate to weight loss). There is a paucity of research examining micronutrient intake on weight loss diets.
Thus, the goal of this study, presented in an article called, “Micronutrient quality of weight-loss diets that focus on macronutrients: results from the A TO Z study” was to look at micronutrient content of four common diets with varying macro’s: Atkins, the Zone, LEARN, and the Ornish.
This is a very crude description of the diets, but Atkins severely restricts carbs, the Zone has a 40/30/30 (carbs/fat/protein) distribution and recommends consuming less than 1700 cals, LEARN focuses on the food pyramid as well as eating less (1200 cals) and moving more, and the Ornish limits total fat to 10% of daily caloric intake.
Subjects were 311 (291 completed) premenopausal women (mean age = 41) who were overweight or obese (BMI ranged from 27-40). They were given books on the diet they were assigned to and then reviewed what they read at weekly one-hour sessions lead by a dietician for eight weeks. They were then to follow the diet for 10 more months (but this study uses 8 weeks as its end point).
Subjects were given “Food Amounts Booklet,” which taught them how to guesstimate their portions. Specific software was used to determine macro- and micronutrients during 24-hour dietary recalls.
I don’t understand why subjects weren’t told to weigh their food for within subject and between subject accuracy. That seems of utmost importance and makes me question the validity of results found. Also, the authors say that at baseline, the mean caloric intake was 1903 cals, but they hadn’t even been taught how to guesstimate (again, not good enough, in my opinion) their intake yet, plus, it is well-known that overweight individuals underestimate the amount they’re consuming (the converse is true as well, by the way). So where did this number come from?
Even though only two of the diets mentioned calories, all groups reported a similar reduction of 500 cals, but each group had a different and statistically significant ratio of macro’s, which make sense given that each diet focuses on a different macro distribution.
The researchers used the Estimated Average Requirement (EAR) values as cutoffs to examine vitamin A, thiamine, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, vitamin C, vitamin E, iron, magnesium, phosphorus, selenium and zinc.
At the end of the eight weeks, the various diets were higher and lower in specific vitamins and minerals. I am ignoring specifics right now, but feel free to ask me or look up the article, if interested.
What is important and noteworthy, however, is that for Atkins, LEARN and the Ornish diets, the risk of inadequacies increased (although, again, not all in the same micronutrients assessed), while, in contrast, the Zone group’s risk of inadequacies decreased at a statistically significant level for several vitamins and the risk didn’t increase for any of the other vitamins or minerals.
Importantly, this masks (and the authors made sort of confusing and downplayed) the fact that although the risk for certain inadequacies decreased, the inadequacies remained. That is, in the Zone diet, while the levels of certain vitamins improved, they still remained at a deficient level. For vitamin E, for example, the risk of inadequacy decreased, yet more than 25% of the women had levels lower than the EAR (proportion of participants deficient went from 80 to 55).
The authors don’t consider this, but it might not solely be the differences in macro distribution (or at least not alone) that are the cause of raising the inadequacies. Subjects’ caloric intake went from a reported average of 1900 to between 1373 and 1478. Lowering calories, especially to that level, and especially when the new diets don’t focus on whole, unprocessed, micronutrient-rich foods, could majorly increase the risk of deficiencies.
I should also note that we don’t know what subjects ate. Maybe providing a representative sample from each diet would have been useful.
I think the take-home message is what I said earlier – that diets don’t = healthier eating. In other words, “[o]f the specific weight-loss diets that are defined largely by their macronutrient content…micronutrient intakes tend to be overlooked,” and further, “micronutrient deficiency should be an important consideration when assessing the overall quality of weight-loss diets.”
ETA: I just looked at US News' "Best Diets for Health," and the Ornish came in at #8, the Zone tied at #11, and Atkins at #20. For weight-loss, Atkins came in at #7, the Ornish tied at #11, the Zone at #18.randi morse, randi.morse@gmail.com, newton, ma
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