Popular diets, particularly those low in carbohydrates, have challenged current recommendations
advising a low-fat, high-carbohydrate diet for weight loss. Potential benefits and
risks have not been tested adequately.
To compare 4 weight-loss diets representing a spectrum of low to high carbohydrate
intake for effects on weight loss and related metabolic variables.
Twelve-month randomized trial conducted in the United States from February 2003 to
October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic,
premenopausal women.
Participants were randomly assigned to follow 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.
Weight loss at 12 months was the primary outcome. Secondary outcomes included 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 Tukey studentized range test was used to adjust for multiple testing.
Weight loss was greater for women in the Atkins diet group compared with the other
diet groups at 12 months, and mean 12-month weight loss was significantly different
between the Atkins and Zone diets (P<.05). Mean 12-month weight loss was as follows:
Atkins, -4.7 kg (95% confidence interval [CI], -6.3 to -3.1 kg), Zone, -1.6 kg (95%
CI, -2.8 to -0.4 kg), LEARN, -2.6 kg (-3.8 to -1.3 kg), and Ornish, -2.2 kg (-3.6
to -0.8 kg). Weight loss was not statistically different among the Zone, LEARN, and
Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable
with or more favorable than the other diet groups.
In this study, premenopausal overweight and obese women assigned to follow the Atkins
diet, which had the lowest carbohydrate intake, lost more weight at 12 months than
women assigned to follow the Zone diet, and had experienced comparable or more favorable
metabolic effects than those assigned to the Zone, Ornish, or LEARN diets [corrected]
While questions remain about long-term effects and mechanisms, a low-carbohydrate,
high-protein, high-fat diet may be considered a feasible alternative recommendation
for weight loss.
clinicaltrials.gov Identifier: NCT00079573.