A very interesting 20year study done by Harvard, the results of which were published in the New England Journal of Medicine early this summer.
http://www.nytimes.com/2011/07/19/he...ewanted=1&_r=1
It disproves the principal that "everything in moderation" is okay in terms of losing or maintaining weight and it lists the foods that are the most harmful and those that are most helpful. A good summary.
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“This study shows that conventional wisdom — to eat everything in moderation, eat fewer calories and avoid fatty foods — isn’t the best approach,” Dr. Dariush Mozaffarian, a cardiologist and epidemiologist at the Harvard School of Public Health and lead author of the study, said in an interview. “What you eat makes quite a difference. Just counting calories won’t matter much unless you look at the kinds of calories you’re eating.”
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The foods that contributed to the greatest weight gain were not surprising. French fries led the list: Increased consumption of this food alone was linked to an average weight gain of 3.4 pounds in each four-year period. Other important contributors were potato chips (1.7 pounds), sugar-sweetened drinks (1 pound), red meats and processed meats (0.95 and 0.93 pound, respectively), other forms of potatoes (0.57 pound), sweets and desserts (0.41 pound), refined grains (0.39 pound), other fried foods (0.32 pound), 100-percent fruit juice (0.31 pound) and butter (0.3 pound).
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But contrary to what many people believe, an increased intake of dairy products, whether low-fat (milk) or full-fat (milk and cheese), had a neutral effect on weight.
And despite conventional advice to eat less fat, weight loss was greatest among people who ate more yogurt and nuts, including peanut butter, over each four-year period.