A study was undertaken to examine the micronutrient intake of people who were on four well-known weight-loss diets, namely Atkins, Zone, LEARN and Ornish. A decrease in calorie intake from baseline was seen in all four groups and was comparable across all groups. At eight weeks, a sizeable proportion of participants were found to have nutrient deficiencies; in the Atkins group for thiamine, folic acid, vitamin C, iron and magnesium; in the LEARN group for vitamin E, thiamine, and magnesium; and in the Ornish group for vitamins E and B-12 and zinc. In contrast, for the Zone group, the risk of vitamins A, E, K, and C deficiencies decreased.
Although micronutrients account for a very minute portion of the diet, they are essential for overall health. Weight-loss diets often concentrate only on changing macronutrient portions of the diet, such as carbs and fat, and ignore the micronutrient content. The Atkins, Zone, LEARN and Ornish diets have different goals. Atkins promotes lower carbohydrate intake; the Zone diet promotes a balanced distribution of carbohydrates, fat and proteins in the ratio 40:30:30. The LEARN diet emphasizes eating less and exercising more. The Ornish diet aims to lower the total fat intake to less than 10 percent of total calorie intake. The present study investigated the micronutrient content of the four diet programs.
* The study recruited 311 premenopausal obese or overweight women aged between 25 and 50 years. Of these, 291 participants completed eight weeks of their assigned diet. They had to then independently continue their diet for 10 months after the inital eight-week period.
* The subjects were assigned to groups. One group of 73 followed the Atkins diet, 73 followed Zone, 73 followed LEARN and 72 followed the Ornish diet.
* Participants’ dietary intake data was collected before the start of the study, again at eight weeks and then again at 10 months. Supplement use data was also collected at baseline and at eight weeks.
The nutrition intake assessment only considered food intake and not the use of multivitamin and multimineral supplements. The data collected was self reported, which is associated with lot of underreporting among dieting and overweight individuals. The study also interpreted differently the dietary iron intakes falling below the standard Estimated Average Requirement (EAR). The nutrient inadequacy of vitamins K and D could not be inferred due to the lack of an established EAR for those micronutrients.
* Energy derived from carbohydrates was lowest in Atkins and highest in Ornish. Percentage of energy from proteins was lowest in Ornish and highest in Atkins. Fiber content of food was highest for Ornish and lowest for Atkins.
* At eight weeks, 25 percent of women had micronutrient intake levels below the estimated average requirement (EAR) by diet groups as follows: thiamine, folic acid, vitamins C and E, iron and magnesium with Atkins; vitamin E and magnesium for Zone; vitamins A, C, and E and magnesium with LEARN; and magnesium, zinc, and vitamins A, B-12, and E with Ornish.
* Zone diet followers actually had a decreased risk of vitmains A, C, and E deficiencies
Popular weight-loss books promoting various combinations of carbohydrates, proteins and fats often neglect the micronutrient portion of food. Only the Atkins diet suggests a broad multiple mineral and vitamin supplement, whereas the other three diets maintained that following the diet excluded the need for supplementation. These weight-loss regimens increase the risk of developing deficiency levels of various micronutrients. For example, the Zone diet group was found to have the maximum consumption of the four diet groups for niacin, vitamins A, B-6, C, and K. The Zone, Ornish and LEARN groups showed higher folic acid intake than the Atkins group. The Atkins and Zone groups’ zinc and selenium intakes were higher than those of the other two groups. Vitamin C, folic acid, thiamine and magnesium intakes were lowest in the Atkins diet. This study’s findings suggest that diets with moderately reduced carbohydrate portions and nutrient dense foods have a comparative micronutrient advantage.
For More Information:
Micronutrient Quality of Weight-Loss Diets That Focus on Macronutrients: Results from the A to Z Study
Publication Journal: The American Journal of Clinical Nutrition, June 2010
By Christopher D. Gardener; Soowon Kim; Stanford University Medical School, Stanford, California
*FYI Living Lab Reports Are Summaries of the Original Research.