Dairy that’s low in lactose (the sugar found in milk), such as heavy cream, butter, and cheese, can be consumed in moderation on a ketogenic diet. Dairy products high in lactose, such as milk and yogurt, should be limited or, for some people, cut out completely. We often find that individuals who are struggling with the diet are consuming too much dairy, and pulling back even slightly can help significantly [1].
Zajac, A., Poprzecki, S., Maszczyk, A., Czuba, M., Michalczyk, M., & Zydek, G. (2014). The effects of a ketogenic diet on exercise metabolism and physical performance in off-road cyclists. Nutrients, 6(7), 2493-2508. DOI: 10.3390/nu6072493