I just came back from vacation yesterday after gorging myself with food and alcohol for an entire week. I ran one night because I got drunk and found myself in the hotel gym. Ran 0.5 miles at 12% incline at 9:00 pace on the treadmill (it was hard). Other than that I didn't do anything except consume maybe 3000-5000 calories a day.
And guess what? Today I weighed myself, as I do mos morning at home (right out of bed before consuming anything), and I was up a mere 0.5 lbs! Based on my caloric intake and the calories in/calories out dictum I should have gained AT LEAST 5lbs. But I didn't. Calories in/calories out is BS.