What intrigues me most is this part:
The total amount of food adds up to four pounds, but it’s only about 1,600 to 1,800 calories, a far cry from the 5,000 calories or more he used to consume every day.
That ties into a line in Michael Pollan's Omnivore's Dilemma that the typical adult can only eat 1500 pounds per year...which is basically four pounds per day. What can vary, among many other things, is the energy density of those four pounds.
But darn it I like my salad dressing and butter :p
Also makes you think about the wisdom of stomach stapling -- which essentially reduces that four pounds per day capability, but lets people still eat very calorie dense foods. I have a friend whose wife underwent the procedure, and it did a world of good -- but I also know he lost his mother to complications from an early stomach stapling back in the 1980s.