In my training runs, I often notice the smell of ammonia, either while I am running or afterwards when I'm cleaning up. I'm assuming I'm producing it as my body burns something for energy for the workout. I notice it more on long training runs, particularly in hard efforts or hot weather, but I don't notice it when racing. I've read that you can produce ammonia if you don't have enough carbs -- I guess that fits my pattern, because in races I'll load up on carbs and gels, where I might be more casual about nutrition on training runs.

Can anyone explain the chemistry? What exactly am I burning to produce ammonia, and am I sweating it out or breathing it out or what? Am I counteracting the benefits of training by working so hard that I'm burning off something I shouldn't be? Is there any benefit to training in "carbo-deficit" so my body will learn to find carbs and fats instead of burning whatever it is I'm burning to produce ammonia?

Thanks!
Lee