I have long suspected this, but actually doing the experiment myself was simply out of the question. Now, though, there is corroboration:
When something sounds too good to be true, well, it probably is. Take “negative-calorie foods” as an example. The notion is that digesting certain foods burns more calories than those foods provide. The faulty logic of this urban legend is based on the scientifically proven thermic effect of food (TEF), which simply means the amount of energy the body uses to digest a food. The thinking goes, if you were to eat a very low-calorie food — common examples include celery, apples, and limes — then you’d actually create a calorie deficit. In other words, these foods would end up costing less-than-zero calories.
Sadly, there are no negative-calorie foods. The TEF generally ranges from 10 percent to 20 percent of the calories in a food. So let’s say a celery stalk has seven calories. Even if you assume a 20 percent TEF, that means you’re still left with about five and a half calories.
In the specific case of celery, chewing the stalk is supposed to expend some smallish number of calories, though 5½ seems a bit high unless you’re one of those people who counts every chew up to N, where N = 32, probably.
Still, that isn’t the biggest problem with celery:
Celery is 90% water and 100% not pizza.
— Emily Thomas (@emitoms) June 16, 2014
Which is almost certainly true.
(Via Violins and Starships.)