Assuming I'm eating say, 1800 calories a day.
You are more likely to loose your life than weight if you train from sun up till sundown.. You can burnup to 1500 an hour on the treadmill, so say you consume 1800 kcal a day and burn 2500 a day, you'll be pretty much fucked in no more than 5 days
Ok, not literally sun up to sun down.
More like 3 hours.