This is a rush transcript from "The Big Story With John Gibson," July 26, 2007. This copy may not be in its final form and may be updated.

GERALDO RIVERA, "BIG STORY" GUEST HOST: In "Big Health" tonight: Have you been packing on pounds? Does your bikini not fit you any more? Well in the great tradition of blaming someone else for your own problems, our own problems, your bulge might be your friend's fault. Get this, a brand new federally funded study just published in the New England Journal of Medicine actually says obesity is quote, "Socially contagious and can spread from one person to another just like an infectious disease." Researchers say even if your fat friend or family member lives on the other side of the country, you could still catch their weight woes long distance. The key we are told is if they think being overweight is acceptable, you might as well. So if you buy this theory and you are hoping to shed the pounds, you might want to at least temporarily to shed some friends fast. Dr. Raj from New York University School of Medicine joins me now. Do you buy it Dr. Raj, welcome?

DR. RAJ, NYU SCHOOL OF MEDICINE: You know I don't really buy the fact that you need to shed your friend and it's contagious like a cold. I think what they're saying is if you happen to have friends who tend to gain a lot of weight and become obese, you may either start to mimic some of their behavior in terms of their diet, that kind of thing, or you might actually think hey, maybe I don't have to work so hard on my own diet, maybe it's ok to gain some weight. So in that way.

RIVERA: But you know I think most of our viewers will agree that when you see a heavy person walking with a spouse, generally they are both heavy and often their children are heavy.

RAJ: Right.

RIVERA: So it's contagious — I guess they mean socially; they don't mean in a viral sense.

RAJ: Right. So I think if you were sharing a home, you're sharing meals with someone, you go out to eat —

RIVERA: Big macs.

RAJ: Exactly, your friend orders nachos, it's hard to say no, that kind of thing. But what's interesting, even if they lived in different cities. So they're not really sharing behaviors. They found this increase in obesity and influence from one friend or another. So you can't explain it all by that kind of shared behavior.

RIVERA: Would it be logical to assume that the converse is true, that if your friends are fit or your family members are fit, you might be more inclined to be fit as well.

RAJ: I definitely think so. There is a lot of social pressure that goes on. Certainly we see in schools, with teenagers, young girls, you know even with things like body image disorders, anorexia, it tends to spread among people. So it definitely can —

RIVERA: And you know thinking about it, when you have one smoker, you are more likely to hang around with other smokers, too.

RAJ: Right, and that's the other —

RIVERA: So there is a social contagiousness.

RAJ: Definitely and there might be people who because they are sort of predetermined or their mind is a certain way that they tend to become obese, they might choose friends that are similar in that way. So maybe that they any way would have been obese and they tend to hang out with people like them.

RIVERA: Well, maybe if one gets the message to straighten out and get healthy, it will spread, too.

RAJ: That's the hope and maybe we should treat people in groups in terms of obesity.

RIVERA: Oh, interesting.

RAJ: Yeah.

RIVERA: Dr. Raj, thanks.

RAJ: Thanks

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