I worked with a young lad a few years ago who did exactly this, likely down to his atrocious diet.
I'd pick him up at 8am and he'd immediately demolish a pack of cajun chicken breast followed by a bag of crisps or 'fridge raiders'.
Then for lunch another pack of chicken, and there was always a large bag of cheese balls or the like on the go throughout the day, washed down with a constant supply of Monster energy drink.
The first thing he'd do when we got to a job is ask the customer if he can use the toilet, before disappearing for 20 minutes. There were some small 1-2 hour jobs where he was in the toilet more than out of it.