Those 15 percent of people might be on to something. A mounting body of research suggests refined sugar may be as addictive as cocaine or morphine—if not more so—says Pam Peeke, M.D., M.P.H., senior science advisor for Elements Behavioral Health and author of The Hunger Fix. Refined sugar causes changes in the brain's reward center, leading to addiction and a downward health spiral that can end in heart disease, type 2 diabetes, and even cancer.