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Various dietary approaches have been proposed, some of which have been compared by randomized controlled trials:
• A comparison of Dr Atkins' diet, Slim-Fast plan, Weight Watchers pure points programme, and Rosemary Conley's found no significant differences.
• A comparison of Atkins diet, Zone diet, Weight Watchers, and Ornish diet noted:
"all 4 diets resulted in modest statistically significant weight loss at 1 year, with no statistically significant differences between diets"
"The higher discontinuation rates for the Atkins and Ornish diet groups suggest many individuals found these diets to be too extreme"
Low carbohydrate versus low fatMany studies have focused on diets that reduce calories via a low-carbohydrate (Atkins diet, Zone diet) diet versus a low-fat diet (LEARN diet, Ornish diet). The Nurses' Health Study, an observational cohort study, found that low carbohydrate diets based on vegetable sources of fat and protein are associated with less coronary heart disease.
An analysis by the international Cochrane Collaboration in 2002 concluded that fat-restricted diets are no better than calorie restricted diets in achieving long term weight loss in overweight or obese people.
A more recent analysis found that low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year.
CholesterolHowever, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-density lipoprotein cholesterol values when low-carbohydrate diets to induce weight loss are considered.
The Women's Health Initiative Randomized Controlled Dietary Modification Trial found that a diet of total fat to 20% of energy and increasing consumption of vegetables and fruit to at least 5 servings daily and grains to at least 6 servings daily:
- no reduction in cardiovascular disease
- an insignificant reduction in invasive breast cancer
- no reductions in colorectal cancer
- additional recent randomized controlled trials have found that:
- A comparison of Atkins, Zone diet, Ornish diet, and LEARN diet in premenopausal women found the greatest benefit from the Atkins diet.
- In young adults found the choice of diet may be influenced by measured insulin secretion:
"Reducing glycemic [carbohydrate] load may be especially important to achieve weight loss among individuals with high insulin secretion"
ExerciseA meta-analysis of randomized controlled trials by the international Cochrane Collaboration found that "exercise combined with diet resulted in a greater weight reduction than diet alone".
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