Newswise — Premenopausal women who were assigned to follow the Atkins diet
for one year lost more weight when compared to women who were assigned to follow
the Zone, Ornish and LEARN diets, according to a study in the March issue of
JAMA.
Overweight and obesity are well-documented problems in the United States.
National dietary weight loss guidelines (a diet low in calories and fat, high in
carbohydrates) have been challenged, particularly by supporters of low-carbohydrate diets. However, limited evidence has been available to effectively evaluate other diets, according to background information in the article.
Christopher D. Gardner, Ph.D., of Stanford University Medical School,
Stanford, Calif., and colleagues examined the effects of four diets-3 popular
and substantially different diets and 1 diet based on national
guidelines-representing a spectrum of carbohydrate intake, on weight loss and
related metabolic variables in overweight and obese premenopausal women. The
diets were Atkins (very low in carbohydrate), Zone (low in carbohydrate), LEARN
(Lifestyle, Exercise, Attitudes, Relationships, and Nutrition; low in fat, high
in carbohydrate, based on national guidelines), and Ornish (high in
carbohydrate). The study, which included 311 overweight/obese (body mass index,
27-40) nondiabetic, premenopausal women, was conducted from February 2003 to
October 2005. Participants were randomly assigned to follow for 12 months the
Atkins (n = 77), Zone (n = 79), LEARN (n = 79), or Ornish (n = 76) diets and
received weekly instruction for 2 months, then an additional 10-month
follow-up.
Besides weight loss, the participants were also measured for lipid profile
(low-density lipoprotein, high-density lipoprotein, and non-high-density
lipoprotein cholesterol, and triglyceride levels), percentage of body fat,
waist-hip ratio, fasting insulin and glucose levels, and blood pressure.
Outcomes were assessed at months 0, 2, 6, and 12.
The researchers found that weight loss was greater for women in the Atkins
diet group compared with the other diet groups at one year. Average 12-month
weight loss was 10.4 lbs for Atkins, 3.5 lbs. for Zone, 5.7 lbs. for LEARN, and
4.8 lbs. for Ornish. At 12 months, measurements for lipids and levels of
insulin, glucose and blood pressure for the Atkins group were comparable with or
more favorable than the other diet groups.
"Concerns about adverse metabolic effects of the Atkins diet were not
substantiated within the 12-month study period. It could not be determined
whether the benefits were attributable specifically to the low carbohydrate
intake vs. other aspects of the diet (e.g., high protein intake). While
questions remain about long-term effects and mechanisms, these findings have
important implications for clinical practice and health care policy. Physicians
whose patients initiate a low-carbohydrate diet can be reassured that weight
loss is likely to be at least as large as for any other dietary pattern and that
the lipid effects are unlikely to be of immediate concern. As with any diet,
physicians should caution patients that long-term success requires permanent
alterations in energy intake and energy expenditure, regardless of macronutrient
content," the authors conclude.