Body Fat: Fact or Fiction?

Frustrated by fat? Healthy food choices and vigorous exercise may not be enough for those who are trying to lose weight. Two new studies tackle how we gain -- and lose -- harmful body fat.

CBS News Medical Correspondent Dr. Jennifer Ashton helped "Early Show" co-anchor Maggie Rodriguez separate fat fact from fiction.

Ashton started off with a fat fact or fiction test.

• Fact or fiction: Thigh fat is healthier than belly fat?

Rodriguez went with belly fat, saying "because I've always heard how bad belly fat is."

"That's good. That means the message is getting out there. We've heard that belly fat or fat that accumulates around our midsection really is a significant risk factor for our health," Ashton explained. "All of the obesity complications like diabetes, insulin resistance, heart disease, really goes up as our waistline goes up."

According to Ashton, the recent study done out of the Mayo Clinic compared where people gained weight, where they gained fat and actually found that those who gained fat on their lower bodies, specifically in their thighs, and we're talking men and women, may -- get ready, may actually have some protective factors against those obesity complications.

Ashton points out that "We're not trying to imply that you want to set out to gain weight around your legs. But it is an area that we'll be seeing more research in. Definitely you want to stay away from gaining weight in your midsection."

Is it true that the more belly fat you have the greater the chance it's between your organs?

"Exactly. And when we do C.A.T. Scans (Computerized Axial Tomography) and look at the organs in our body you can see fat between these organs called visceral fat. And that is really dangerous to your health," Ashton said.

• Fact or fiction: You can spot reduce fat.

"Absolutely not because I've been trying to get rid of this post-pregnancy pooch and it's not happening," Rodriguez said.

"Most people today know this. But in the past people really did think you could 'spot reduce.' That was the term. But most people also know that everyone is individual. Where they lose weight tends to be characteristic for them. A lot of people will lose it in their face first and the saying is we're not doing crunches or face exercises," Ashton said. "So, bottom line, you want to lose weight gradually throughout your entire body, with individual differences taken into account. Some people may gain it or lose it faster in their legs. But definitely cannot spot reduce."

• Fact or fiction: Sleep loss can limit fat loss?

"Well this one I confess, I saw the study out today which confirms, which I already knew because we live this schedule. It's absolutely true," Rodriguez said.

"Exactly. We have been hearing a lot more about this. Not only does America have an obesity problem, America also has a sleep problem," Ashton said.

The study looked at people who got more or less than 8 1/2 hours of sleep, which was their target number. And those who got less than 8 1/2 hours of sleep a night were hungrier during the day, and lost 40 percent or more muscle mass, which is a problem, Ashton points out. When you want to lose weight you want to keep your lean muscle mass, so it really works two ways.

"But does anyone realistically get eight hours of sleep anymore?" Rodriguez asked.

Ashton says she does.

"But that's because I go to bed at 9:00 p.m." Ashton admits. "Everything is a tradeoff. Sleep is critically important. It does stimulate the hunger hormone during the day. So you really, when you're dieting, you want to diet, exercise, and sleep."

• Fact or fiction: You can work off a month of bad eating. A lot of people with the holidays coming up with just going to be eating very poorly around Thanksgiving and Christmas.

Rodriguez said fact.

"You actually cannot work off a month of bad eating, Maggie. Sorry," Ashton said. "Now very important and I want to emphasize this -- it's never too late to reverse bad habits or damage from let's say a month or two months of bad eating and no exercise.

"But this study actually found that the damage done in our bodies, in our fat cells, persists even up to months or years after you had that bad month. So really, it's day-to-day, it's hour-to-hour, it's meal-to-meal, and you want to have those good habits in place, all of that time."