Haha "I hope NOW you understand that." Are you out on the internet just to argue?
No diet, regardless of exercise would ever be healthy in any sense of the word if you ate 12k calories of Pizza.
Balanced diets and regular exercise is important and these food types are not normal.
And you are remembering his diet wrong....he never ate anything like that.
He ate a variety of foods and even those aren't healthy.
"But these kinds of calculators donâ(TM)t really apply to a someone like Phelps, who exercises way more vigorously than the typical person, says Kathleen Laquale, an athletic trainer and nutritionist who teaches at Bridgewater State College in Massachusetts. Even by athletic standards, Phelps is in his own league."
So he isn't exercising normally/properly. He's way off the chart in the extremes that most people's bodies would need years to condition to without damage.
Is that really true? There is no way to avoid this in the US without choosing your home location that carefully?