This is one of those beauty-things where experts have conflicting ideas about it – one minute it’s “yes”; the next minute it’s “no”.
However, I believe that at the end of the day, you know your own body, and as far as junk food giving you acne… I believe it really depends on the person, and their skin type. (That being said, Do You Really Know Your Skin Type?)
So, does junk food cause acne? My thought is this: if you already suffer from acne and have a predisposition for it (genetics, bad luck, etc), junk food, I believe, will definitely affect your skin.
For example, I struggled with acne as a teen, and still get zits now and again, especially if I overdo it with eating greasy burgers, fries, chips, candy. It’s fine in small amounts, but one week of a bad diet? Guarantee monster zits. Funnily enough, actually, anything with dairy gives me zits, which kinda makes sense because dairy is pretty inflammatory (one of the reason why, whenever someone asks me for acne help, I tell them stop eating dairy). Same with my other friend who has acne prone skin – she can’t have chocolate without breaking out. But for my friends who have naturally clear skin, they can eat whatever they like and their face is still fine.
So the answer is yes and no – but it all depends on your acne situation already: Junk food will probably cause acne if you are already have a history with acne; but if not, you’re totally fine. (And I’m totally jealous.)