Cereal Diet For Weight Loss: Does It Work? Cereal diet promises to help shed some weight through a simple and easy-to-follow routine. Unlike other plans that require a number of adjustments, this diet only encourages people to replace breakfast and lunch with cereal and milk. The cereal diet became popular after the “Special K Challenge.” The manufacturer already stopped promoting the challenge but many people continued to follow and recommend eating cereal and milk daily for weight loss. Followers of the diet said it provides good amounts of fiber and whole grains and lower fat and calories.