That was likely, literally in his case, the only thing he was consuming all day.  If you watch Super Sized Vs Super Skinny (Youtube has episodes) it pairs together two people with horrible diets- one who is under a healthy BMI and one who is morbidly obese- to switch diets and showcase how neither is what a person should be living on.  Some of the underweight individuals eat nothing but candy, soda, or energy drinks but they ate such tiny portions that they were still barely sustaining their low body weight.  I could totally see one such individual developing type 2 diabetes if the eating habits are prolonged enough. Fats will eat the 8 Cinnabons and say "oh this is all I've had to eat today, I'm just so hungry!!" but they don't count (or remember) the juice, sodas, or fancy coffees, the nibbles at chips/cookies/chocolates throughout the day, any kind of food portion that is "too small" in their minds like a bit of soup or small side salad (nor do they count the tablespoons of dressing), and they don't count alcohol which is HUGE.  Your friend probably (because science) ate almost nothing for the rest of the day and does not eat 8 Cinnabons every day.  In fact, I wouldn't be surprised if those kinds of binges for him are a once-every-couple-weeks kinda thing, and serve to offset his lack of eating much else.