The breakdown....

Two-thirds of his total intake came from junk food. He also took a multivitamin pill and drank a protein shake daily. And he ate vegetables, typically a can of green beans or three to four celery stalks.

also
For a class project, Haub limited himself to less than 1,800 calories a day. A man of Haub's pre-dieting size usually consumes about 2,600 calories daily. So he followed a basic principle of weight loss: He consumed significantly fewer calories than he burned

and finally ....
ate one of these sugary cakelets every three hours, instead of meals. To add variety in his steady stream of Hostess and Little Debbie snacks, Haub munched on Doritos chips, sugary cereals and Oreos, too.

so there ya go, energy balance is very simple, less in more out. He was also fulfilling his DRV of nutrients and micronutrients via the vitamins he was consuming, and you have to remember he didn't have to work out to burn calories. Basal metabolic rate amounts to the calories you burn per hour every day just living and can add up quick. There are many formulas for active, sedentary and those in between.

Go State!