Drink until your liver shuts down and you'll drop a third of your weight in a month; so technically, yes, you can lose weight eating only In N' Out.
Goddamnit now I want a milkshake and a protein-style double double.
The closest In n Out to me is 1142 miles and would take an estimated 92hrs by bicycle. If I did this and didn't lose weight it's probably because I got killed attempting to get there or back.
Goddamnit now I want a milkshake and a protein-style double double.