Neck sweats do what they say, sweat the water out of a horse's neck area. Kind of like one of those sauna wraps a person will do. Personally I have never used them. Only one good way to burn fat is diet and exercise. Genetics play a lot of where horses store their fat, some in the crest, others in the stomach, etc. I feel like neck sweats are a short-term solution and wouldn't use them. Especially if the horse is just a pasture puff, there's no use trying to sweat the fat out of his neck if he's unhealthy everywhere else.