Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women

Department of Medicine, Stanford University, Palo Alto, California, United States
JAMA The Journal of the American Medical Association (Impact Factor: 35.29). 03/2007; 297(9):969-77. DOI: 10.1001/jama.297.9.969
Source: PubMed


Recent trials indicate that low-carbohydrate, nonenergy-restricted diets are at least as effective as traditional low-fat, high-carbohydrate diets in promoting weight loss for up to a year. These trials were, however, limited in many respects. The A TO Z (Atkins, Traditional, Ornish, Zone Weight Loss Study compared four diets representing a wide range of carbohydrate intake in 311 overweight or obese premenopausal women 25 to 50 years of age. The participants had a body mass index (BMI) of 27 or higher but were not diabetic. They received instruction weekly for the first 2 months of the l2-month trial and were randomly assigned to follow one of four diets: Atkins (very low in carbohydrate); Zone (low in carbohydrate); LEARN (Lifestyle, Exercise, Attitudes, Relationships, and Nutrition, a diet low in fat and high in carbohydrate); or Ornish (very high in carbohydrate). At no time was total energy intake different in the various groups, but reported energy intake decreased significantly relative to baseline. Mean weight loss over 12 months was greater for the Atkins group (4.7 kg) than for the Zone (1.6 kg), LEARN (2.2 kg), or Ornish (2.6 kg) groups. The difference between the Atkins and Zone groups was statistically significant. Changes in BMI, percentage body fat, and waist–hip ratio paralleled those in body weight. Changes in high-density lipoprotein cholesterol and triglycerides favored the Atkins group at all follow-up intervals. Mean blood pressure levels declined most markedly in the Atkins group at all intervals. Not only was the Atkins diet more effective than the other three diets tested in these overweight or obese premenopausal women, but it also had more favorable metabolic effects. Concern over possible adverse metabolic effects from this low-carbohydrate, high-protein, high-fat diet was not confirmed. Regardless of which diet is tried, patients should know that long-term success requires permanent changes in energy intake and energy expenditure.

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    • "Could the metabolic and endocrine adaptations to carbohydrate restriction result in augmented body fat loss compared to an equal calorie reduction of dietary fat? Several randomized controlled trials have demonstrated greater short-term weight loss when advising obese patients to restrict dietary carbohydrates (Foster et al., 2010; Gardner et al., 2007; Shai et al., 2008), but such outpatient studies are difficult to interpret mechanistically because it is not currently possible to accurately measure adherence to the recommended diets since the instruments for assessing food intake rely on selfreport and have been demonstrated to be biased (Winkler, 2005). Therefore, outpatient studies cannot determine to what extent any observed differences in weight loss are due to a metabolic advantage of reduced carbohydrate diets versus a greater reduction in overall energy intake. "
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    ABSTRACT: Dietary carbohydrate restriction has been purported to cause endocrine adaptations that promote body fat loss more than dietary fat restriction. We selectively restricted dietary carbohydrate versus fat for 6 days following a 5-day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Subjects received both isocaloric diets in random order during each of two inpatient stays. Body fat loss was calculated as the difference between daily fat intake and net fat oxidation measured while residing in a metabolic chamber. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002). Mathematical model simulations agreed with these data, but predicted that the body acts to minimize body fat differences with prolonged isocaloric diets varying in carbohydrate and fat. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · Aug 2015 · Cell metabolism
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    • "Dietary intervention is often the first line of defense against CVD, so it is important to understand how diet can affect postprandial endogenous TAG concentrations. It has been established that the composition and duration of dietary interventions can have a profound impact on the rate of hepatic TAG secretion during the fasted state (Abumrad et al. 1978; Boivin and Deshaies 1995; Brons et al. 2009; Cahova et al. 2012; Gardner et al. 2007; Harber et al. 2005; Mittendorfer and Sidossis 2001; Roberts et al. 2008), but the effects of diet composition on fed-state hepatic TAG secretion is less clear. Thus, the aim of this study was to examine how LF and HF diets alter fed-state hepatic TAG secretion, the protein expression of key enzymes involved in TAG assembly and secretion, FAO, and the fatty acid profile of stored TAG in an animal model of obesity (Levin et al. 1997). "
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    ABSTRACT: The purpose of this study was to compare the effects of short-term low-fat (LF) and high-fat (HF) diets on fed-state hepatic triacylglycerol (TAG) secretion, the content of proteins involved in TAG assembly and secretion, fatty acid oxidation (FAO), and the fatty acid profile of stored TAG. Using selectively bred obese-prone Sprague-Dawley rats, we directly measured fed-state hepatic TAG secretion, using Tyloxapol (a lipoprotein lipase inhibitor) and a standardized oral mixed meal (45% carbohydrate, 40% fat, 15% protein) bolus in animals fed a HF or LF diet for 2 weeks, after which the rats were maintained on their respective diet for 1 week (washout) prior to the liver being excised to measure protein content, FAO, and TAG fatty acid profiles. Hepatic DGAT-1 protein expression was ∼27% lower in HF- than in LF-fed animals (p < 0.05); the protein expression of all other molecules was similar in the 2 diets. The fed-state hepatic TAG secretion rate was ∼39% lower (p < 0.05) in HF- (4.62 ± 0.18 mmol·h(-1)) than in LF- (7.60 ± 0.57 mmol·h(-1)) fed animals. Hepatic TAG content was ∼2-fold higher (p < 0.05) in HF- (1.07 ± 0.15 nmol·g(-1) tissue) than in LF- (0.50 ± 0.16 nmol·g(-1) tissue) fed animals. In addition, the fatty acid profile of liver TAG in HF-fed animals closely resembled the diet, whereas in LF-fed animals, the fatty acid profile consisted of mostly de novo synthesized fatty acids. FAO was not altered by diet. LF and HF diets differentially alter fed-state hepatic TAG secretion, hepatic fatty acid profiles, and DGAT-1 protein expression.
    Full-text · Article · Apr 2014 · Applied Physiology Nutrition and Metabolism
    • "A 2006 meta-analysis including 5 randomized controlled trials showed that low-carbohydrate diets resulted in significantly more reduction in body weight than isocaloric low-fat diets at 6 months (net changes À3.3 kg, 95%CI: À5.3 to À1.4), but non-significantly more reduction at 12 months (net changes: À1.0 kg, 95%CI: À3.5 to 1.5) [23]. Those on low-carbohydrate diets experienced a similar reduction in fat mass and non-fat mass as those on low-fat diets, so that the changes in body composition were not significantly different between the two diets [9] [14] [15] [17] [18] [20]. Low-carbohydrate diets may have the added benefit of decreasing the risk of central obesity. "
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    ABSTRACT: Aims Obesity is an important public health issue because of its high prevalence and concomitant increase in risk of cardiovascular diseases. Low carbohydrate diets are popular for weight loss and weight management but are not recommended in leading guidelines due to the perception that increases in dietary fat intake may lead to an adverse cardiovascular risk profile. To clarify the effects of a low-carbohydrate diet for weight loss on cardiovascular disease risk factors as compared to a low fat diet for weight loss, we systematically reviewed data from randomized controlled clinical trials and large observational studies. Data Synthesis We searched the MEDLINE database (Jan 1966 - Nov 2013) to identify studies that examined a low-carbohydrate diet as compared to a low-fat diet for weight loss or the improvement of cardiovascular disease risk factors. Conclusions Recent randomized controlled trials document that low-carbohydrate diets not only decrease body weight but also improve cardiovascular risk factors. In light of this evidence from randomized controlled trials, dietary guidelines should be re-visited advocating a healthy low carbohydrate dietary pattern as an alternative dietary strategy for the prevention of obesity and cardiovascular disease risk factors.
    No preview · Article · Apr 2014 · Nutrition, metabolism, and cardiovascular diseases: NMCD
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