In "The Fat Trap" (Jan. 1), Tara Parker-Pope implied that obesity is virtually incurable based on the observation that eating calorie-restricted diets (less than 1,200 or 1,500 calories a day) doesn't cure it. Maybe this treatment doesn't work, though, because it's the wrong treatment. Fat accumulation in the human body is regulated primarily by the hormone insulin; we secrete insulin primarily in response to the carbohydrates we consume. These facts support an endocrinological view of obesity as a hormonal disorder caused by carbohydrate-rich foods, particularly refined grains and sugars, elevating insulin levels. Clinical trials repeatedly demonstrate that obese individuals who consciously restrict carbohydrates but not calories lose weight - often without hunger - while experiencing significant improvements in heart-disease and diabetes risk factors. Those of us who have lost weight ourselves and/or witnessed the effect of these diets on our patients can confirm that this is exactly what happens. GARY TAUBES AND PETER ATTIA, M.D. The letter, signed by more than 250 medical experts, can be read in its entirety at www.ipetitions.com/petition/response-to-nytimes-the-fat-trap/.