On countless food packages, serving sizes have become a confusing joke. I bought a frozen “personal pizza.” That’s what it said on the package, in big letters. From the name (and its size -it’s not very big), you would think a “personal pizza” is for one person – say, you. But according to the small print, it can feed both you and some other person: The serving size listed on the label is half a pie.

We took the “personal pizza” downtown to Little Italy in New York City for some expert opinions.

“I don’t think you could share this with anybody!” said Francesco of Sal’s Pizzeria.

One pizza baker said if he offered one of these little pizzas to his customers, “They’d throw it back in my face!”

Most people we talked to couldn’t believe the recommended serving size for the “personal pizza.” One young woman said, “My cat could eat that.”

Why should we care what sleight-of-hand a company pulls on its label when describing serving sizes? Because people worried about their health need information – and the information on the label is all based on the serving size. Unless people take their calculators with them when they shop, it’s easy to get confused.

Most people would eat one blueberry muffin for breakfast. When the label tells you there are just 215 calories per serving, you’d think it was a reasonably low-cal breakfast. But the label in tiny print on one muffin ABC News bought also said the serving size was one-third of a muffin. If you ate the whole muffin, your light breakfast would be heavier than you expected – and soon you might be, too: That “215 calorie per serving” muffin is really a 645-calorie bomb.

Most shoppers would probably pick up a Swanson’s Hungry Man turkey pot pie at the grocery store and assume it’s a single serving. After all, it’s supposed to feed a hungry man. Yet the label says there are approximately two servings per pie. (Approximately two? I’m sharing my pot pie with an approximate person now?)

So shouldn’t there be some sort of standard on serving sizes? Guess what: There is. As usual, a government “solution” has created more problems.

In the early 1990s, our government summoned the food industry and had it test, weigh and measure 139 different types of food. Then the government determined the amount each of us would customarily eat. So now food companies have government support if they design labels that list absurd serving sizes. And why would they want to list absurdly small serving sizes?

“It’s to make more money and to make people think they’re eating healthier than they are,” one shopper told me.

Right. If the label said that blueberry muffin had 645 calories, some people might not buy it.

None of the food companies that used the deceptive labels would talk to me about this, which is too bad because I’d love to know how an olive company came up with 1.5 olives as its serving size. A jar of smaller olives, which lists 14 as a serving, seems a lot more honest. Who would ever eat 1.5 olives? The folks we talked to at the mall wouldn’t. “What, are you going to throw away half of it?” one woman asked.

If you like pickles and want one serving, you might have to throw away a piece of pickle, too: A jar of Vlasic Polish dill pickle spears lists three-quarters of a spear as the serving size.

People commonly eat three or four pickles as a snack, yet Tim Baker, who owns New York’s Guss’ Pickles, says that a spear is a quarter of a whole pickle. So if you eat three-quarters of a spear, “you only get three-quarters of a quarter of a pickle.”

So carry a calculator, or practice your arithmetic. If you do the math, you can choose your fat and calorie intake based on the facts about real portions.

But as usual, letting the government do the work is a good way to make bad decisions. Did you really think federal regulations were going to make something easier to understand?

Give Me a Break.

Mr. Stossel is co-anchor of ABC News’s “20/20” and the author of “Give Me a Break,” just released in paperback.