Calories are a measure of energy, actually. You can't avoid calories -- you have to eat to live, and calories measure the energy you get from eating, in essence. What you're reading is about weight, not really about calories. Calories are one measure of the amount of food you're taking in, but don't actually measure weight gain or loss very well -- that is best measured, or let's say, dealt with by how well or poorly you metabolize what you're eating. For example, a key measure is how quickly a particular food metabolizes into sugar after you eat, because the quicker that happens the quicker it has to be burnt off or it will store as fat. Calories are more complex, as some high calorie foods don't pose a weight gain problem and some relatively low calorie foods do. But without calories, you'd be dead. With too few, you lack the energy to do anything. With too many, you can't use them, which is one way of saying you're eating more than your body can handle. In your case, if you have a weight problem, it would be that you're too thin to do what you need to do, but that is clearly not the case as you're athletic and I'm assuming that means you have plenty of energy. It is healthier to be too thin than to be too heavy, as the more weight a person has the more stress it puts on everything the body has to do. Research isn't great, but thinner people are thought to live a healthier life than overweight people. Whether they live longer is up for argument. If you consume more calories than your body can efficiently digest, you will stress out your digestive system and the body's breaking down of what you eat into component nutrients and sending them where they need to go. If you do this for too long, this stress might be harmful. You'd probably know, though, because you'd feel too full most likely and would possibly have some problems with evacuation. Some people are just born to be thin and some are born not to be, and there's only so much one can do about that, but if you're way too thin that's a sign of a problem especially if you're eating a lot -- it might be a sign your body isn't properly absorbing what you're eating. How much someone notices this kind of thing depends on what's going on with them individually and how old they are -- many things don't bother us until we get older even though they've been harmful for us all along. We just don't notice until the body gets too old to compensate for it. There's nobody who can probably tell you, if you're healthy and feel fine and your physicals don't show any nutrient deficiencies, if you're skinny by nature or because of something else, so if you do feel fine, and everything's going well, and you don't find yourself lacking energy and you don't get sick a lot, no sense in worrying about it. Peace.