I certainly am not saying that the calorie system is the cause of obesity! But the differences in the nut study were in the range of ~20%-25%, which is certainly not insignificant. In fact, they’re huge. And while I agree with you that this 20% is not enough to make the difference between becoming obese and maintaining your weight, it does the color the way we look at food. People make decisions every day to buy one product over another based on calorie counts. If calorie counts are overestimated in certain foods, these foods are chosen less often by calorie-conscious people. A bias, intentional or not, creeps into our food selection system. It’s like when the “low calorie” label was created and a whole new category of low-calorie products sprang up overnight.