The best long-term diet is a balanced one with healthy carbohydrates (low in grain and starchy carbohydrates). Most importantly, the researchers admit that all calories are not created equal. The results were published in the June 27th issue of Journal of the American Medical Association (JAMA). Here are the details:
Diet 1: The low-fat diet, which had a high glycemic load, was designed to reflect conventional recommendations to reduce dietary fat, emphasize whole grain products, and include a variety of vegetables and fruits.
Diet 2: The low–glycemic index diet aimed to achieve a moderate glycemic load by replacing some grain products and starchy vegetables with sources of healthful fat and low–glycemic index vegetables, legumes, and fruits.
The low-fat and low–glycemic index diets had similar protein and fiber contents.
Diet 3: The very low-carbohydrate diet was modeled on the Atkins Diet and had a low glycemic load due to more severe restriction of carbohydrate. Reserachers provided 3 grams of fiber with each meal (Metamucil, Procter & Gamble) during the very low-carbohydrate diet as recommended.
To ensure micronutrient adequacy and minimize the influence of micronutrient differences among all test diets, they gave each participant a daily multivitamin and mineral supplement.
This is a direct quote from the researchers: "The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective. During isocaloric feeding following weight loss, Resting Energy Expenditure (REE) was 67 kcal/day higher with the very low-carbohydrate diet compared with the low-fat diet. Total Energy Expenditure (TEE) differed by approximately 300 kcal/day between these 2 diets, an effect corresponding with the amount of energy typically expended in 1 hour of moderate-intensity physical activity."
Although the very low-carbohydrate diet produced the greatest improvements in most metabolic syndrome components examined herein, they identified 2 potentially deleterious effects of this diet. Twenty-four hour urinary cortisol excretion, a hormonal measure of stress, was highest with the very low-carbohydrate diet. Higher cortisol levels may promote adiposity, insulin resistance, and cardiovascular disease, as observed in epidemiological studies. C-reactive protein also tended to be higher with the very low-carbohydrate diet in our study.
"In conclusion, our study demonstrates that commonly consumed diets can affect metabolism and components of the metabolic syndrome in markedly different ways during weight-loss maintenance, independent of energy content.
The low-fat diet produced changes in energy expenditure and serum leptin that would predict weight regain. In addition, this conventionally recommended diet had unfavorable effects on most of the metabolic syndrome components studied herein.
In contrast, the very low-carbohydrate diet had the most beneficial effects on energy expenditure and several metabolic syndrome components, but this restrictive regimen may increase cortisol excretion and CRP.
The low–glycemic index diet appears to have qualitatively similar, although smaller, metabolic benefits to the very low-carbohydrate diet, possibly without the deleterious effects on physiological stress and chronic inflammation.
These findings suggest that a strategy to reduce glycemic load rather than dietary fat may be advantageous for weight-loss maintenance and cardiovascular disease prevention."