Consciously eating an unreasonable and/or unnecessary amount of greasy/unhealthy/junky food.
"Remember how Jeff said he was going to stick to Paleo for a month to try it out? Well, I saw him garboloading at the casino buffet last weekend, so I guess it didn't take."
Eating insane amounts of carbs before extreme physical activity in order to have more energy. Typically, this is achieved by eating straight up bread in large amounts.
Before the cross-countryrace, Richard practiced carboloading by eating an entire loaf of bread.