I guess you will look a bit thinner yes, longest I've gone was 14 days and I was fine but had a lot of fat and water weight to drop, you will just gain it back if you're going back to your normal eating and water retention. 

If the goal is just to look different in a week yes, but you're always going to be better off cutting calories in combination with more calorie burning, that can be more walking if you're not much of a exercise person