Epidemiologic investigations can provide insights to the diet-disease relationship in different populations. Slow but continual intake of small amounts of energy in excess of energy needs leads to obesity. Although experimental obesity in animals eating a low-fat diet is the exception, development of obesity in animals eating high-fat diets is the rule. Subjects who were placed on a low-fat diet lost weight, even when weight loss was not the goal of the study. The intake of carbohydrates as sugar and high fructose corn syrup in beverages may have detrimental health effects, since the compensation for oral intake of calorically sweetened beverages is inadequate. Low-carbohydrate diets appeared to produce more weight loss for the first 6 months but not thereafter.