My experience is theirs. I grew up in a household that never had any real money issues, and was consistently fed UPFs. Drank probably around 6 sodas per day. Then one day I said "I'm tired of being fat. Why am I fat? Maybe its because I eat so much junk food, since it is well known that junk food makes you fat." So I stopped eating junk food and now I'm not fat. My parents and other people I knew in my hometown, meanwhile, continued eating junk food, and have continued to gain weight. I will firmly classify this as "their fault".