The American Red Cross agrees. We set up our own experiment with those skeptical swimmers. We had them climb out of the pool and eat a snack. We had them get back in the pool and swim vigorously.
Everybody in class felt fine. One swimmer even said he was hungry.
We tried a tougher test. We asked John Jay's varsity swim team to help. We wanted to see if they could still swim like elite athletes — after eating like couch potatoes.
They all ate a Quarter Pounder and French fries and then swam five laps of sprints.
Even after a heavy, high-fat meal, the swimmers did just fine in the pool.
So the message is: Listen to your body, not your mother. No one recommends you eat a five-course dinner and then swim a marathon. But splashing around or swimming slowly with a full belly is fine.
MYTH # 3 — Are We Destroying Our Forests?
Lots of Americans feel bad when they see images of trees being cut down, because they've been told that America's running out of forestland.
Carl Ross, of the group, Save America's Forests, says we've cut way too much.
"The loss of natural forests in America is a crisis," he said. "And we will lose species forever, and they'll go extinct, if we don't take action now."
Other environmental groups run ads warning of the dire consequences.
But The U.S. Agriculture Department says America has 749 million acres of forestland. In 1920, we had 735 million acres of forest.
We have more forest now. How can that be? One reason is technology that allows us to grow five times more food per acre — so we need less farmland. Lots of what once was farmland has reverted to forest.
But Ross says we don't really have more forests. "We have more areas, in America, with trees on them, that's true. But we have less that are natural," he said.
He's right that many of the oldest trees have been cut down, and about 7 percent of America's forests have been planted by man, but that still means that 93 percent are natural.
Ross is also concerned that loss of old-growth forest is leading to a loss of biodiversity. But while some species have decreased, the populations of many others animals have actually increased in the past 75 years.
Michael Shermer says many people believe America is destroying the forests because environment groups need to scare people to raise money.
"The fear is there," he said, "because, if your goal is to raise funds you have to scare people. You can't tell people things are getting better, and here's the data. You have to tell people things are worse."
The truth, however, is that today in the United States there are two acres of forestland for every single person, and America is growing more forest than it cuts.
MYTH # 2 — Do Expensive Skin Creams Always Work Better?
In the multibillion-dollar skin cream industry, many consumers believe the most expensive product is the most effective.
ABCNEWS examined a few products, with the help of a group of women in their 30s and 40s looking to reduce their wrinkles and age a bit more gracefully.
One volunteer, Christine, was sent to try the most expensive skin cream she could find: Cle de Peau Beaute, La Crème, an anti-aging cream ringing in at $450 per ounce.
Christine was placed on a strict skincare regimen for three months using a gentle cleanser, sunscreen and La Crème every day.