A review written by University of Ontario researchers and published in The Lancet’s Child and Adolescent Health argues that teen consumption of junk food undermines self-regulatory processes in adolescent brains that are working to grow brain development of regulatory control, creating a vicious circle.  Avoiding junk food, they argue, helps brain development and high-calorie, nutrient poor food impedes development.  The review itself is behind a paywall at https://www.thelancet.com/journals/lanchi/article/PIIS2352-4642(19)30404-3/fulltext, but you can find an excellent summary of the review at Neuroscience News:  https://neurosciencenews.com/fast-food-neurodevelopment-15889/