To a certain degree, it also depends on what they do when the cameras aren’t rolling. I remember someone else from the food network getting asked how she stays so thin when she eats so much. She said that she only eats like that on camera, the rest of the time she eats normally and exercises, a lot.
I thought it was Giada, but it looks like it was Katie Lee (who I don’t recall hearing of in the past)
“When I’m filming, I make sure to get up in the morning and exercise, so at least I’m starting my day off right. I learned quickly that if you eat everything [on set], you will feel terrible at the end of the day. So I’ll take a couple of bites, and then I walk away.”
The only thing I could find from Giada, and I don’t remember reading it in the past, was this:
“Giada tapes sometimes three episodes in one day, and they do multiple takes on a close-up of her eating. She doesn’t always eat and swallow every time, since they can do sometimes six to 10 takes with three episodes a day, and that would be like eating six to eight meals a day . . . The bottom line is, she most certainly does eat the food she prepares on the show, but does not always consume the whole dish, as that would be too much for most people to eat in one day.”
That statement appeared to be from her rep trying dance around the fact(?) that she spits a lot of the food out and has a stand in for close ups.
ETA: here’s something I posted in 2011:
I’m always surprised at how many people forget this…for a lot of the food network people, not just Adam. I was watching some behind the scenes type show where they were talking to some Food Network judge and asking how she stays so small when she eats SOOOO much. She explained, as you might guess, that she only eats SOOOO much on the day they shoot and the rest of the week (and the entire off season) she eats like a normal person and exercises as well.
Same goes for Adam, it’s not like he sits at home all week and thinks “Hmmm, today I’ll see if I can eat THREE boxes of cereal in 15 minutes” or “Yesterday I had an entire gallon of ice cream, might as well try for two tonight!”