Good Calories, Bad Calories has much useful information and is well worth reading. Gary Taubes's tenets related to obesity can be summarized in four statements (i) He believes that you can gain weight and become obese without a positive energy balance; (ii) He also believes that dietary fat is unimportant for the development of obesity; (iii) Carbohydrate, in his view, is what produces obesity and (iv) Insulin secreted by the carbohydrate is the problem in obesity. However, some of the conclusions that the author reaches are not consistent with current concepts about obesity. There are many kinds of obesity, and only some depend on diet composition. Two dietary manipulations produce obesity in susceptible people: eating a high-fat diet and drinking sugar- or high-fructose corn syrup-sweetened beverages. Insulin is necessary but not sufficient in the diet-dependent obesities. When diet is important, it may be the combination of fat and fructose (the deadly duo) that is most important. Regardless of diet, it is a positive energy balance over months to years that is the sine qua non for obesity. Obese people clearly eat more than do lean ones, and food-intake records are notoriously unreliable, as documented by use of doubly labelled water. Underreporting of food intake is greater in obese than in normal-weight people and is worse for fat than for other macronutrient groups. Accepting the concept that obesity results from a positive energy balance does not tell us why energy balance is positive. This depends on a variety of environmental factors interacting with the genetic susceptibility of certain individuals. Weight loss is related to adherence to the diet, not to its macronutrient composition.