You can eat nothing but junk food and stay thin as long as the calories add up right. Sure you won't have the best body composition unless you're careful with macros and you likely won't feel very good or be very healthy on the inside, but hams don't even have the "healthy food tastes bad so I can't be thin" excuse for being mayo tankers. Hell, even losing weight eating nothing but junk will likely IMPROVE your health markers until you reach a normal weight vs. eating only the cleanest "organic, non-GMO, superdupervitamin-rich" foods but staying obese.