 It's not just about digestive upset. Everyone knows that if you're switching the feed, you do it gradually over seven to 10 days. But what they don't realize is that dog's system is kind of like going on one of those no-carb diets for people or whatever. Your system actually changes. And to switch to a higher carbohydrate diet in the summer and then switch to a higher fat diet in the winter, it's really you're not doing your dog any favors. You're better off just keeping your dog on a higher protein and fat diet