Stop Subsidizing Childhood Obesity Act - Amends the Internal Revenue Code to deny a tax deduction for expenses related to advertising and marketing primarily directed at children to promote the consumption by children of: (1) food from any fast food restaurant, (2) food of poor nutritional quality, and (3) any brand under which the majority of products are food of poor nutritional quality. Defines "food of poor nutritional quality" as food and beverages that are determined by the Secretary of the Treasury (in consultation with the Secretary of Health and Human Services [HHS] and the Federal Trade Commission [FTC]) to be inconsistent with the most recent dietary guidelines published under the National Nutrition Monitoring and Related Research Act of 1990.