Dietary guidelines have changed over the years as research becomes more accurate in determining what we should eat to attain optimal health and weight. The strongest evidence to date shows that calories matter, but focusing on food quality is an equally important part of preventing weight gain and promoting weight loss.

Focus on eating high-quality foods in appropriately sized portions. It’s no secret that the amount of calories people eat and drink has a direct impact on their weight: Consume the same number of calories that the body burns over time, and weight stays stable. Consume more than the body burns, weight goes up. Less, weight goes down. But what about the type of calories: Does it matter whether they come from specific nutrients-fat, protein, or carbohydrate? Specific foods-whole grains or potato chips? Specific diets-the Mediterranean diet or the “Twinkie” diet? And what about when or where people consume their calories: Does eating breakfast make it easier to control weight? Does eating at fast-food restaurants make it harder? There’sample research on foods and diet patterns that protect against heart disease, stroke, diabetes, and other chronic conditions. The good news is that many of the foods that help prevent disease also seem to help with weight control-foods like whole grains, vegetables, fruits, and nuts. And many of the foods that increase disease risk-chief among them, refined grains and sugary drinks-are also factors in weight gain. Conventional wisdom says that since a calorie is a calorie, regardless of its source, the best advice for weight control is simply to eat less and exercise more. Yet emerging research suggests that some foods and eating patterns may make it easier to keep calories in check, while others may make people more likely to overeat.

This article briefly reviews the research on dietary intake and weight control, highlighting diet strategies that also help prevent chronic disease.