I have a hard time answering your question, because I don't believe the top professional bellydancers are likely to have fat bellies ... at the professional level, bellydancers are subject to the same rigors of fitness and training as a dancer of any other genre.

Perhaps the answer to your question lies in the fact that bellydance is different from other serious dance genres in that so many adults perform in public when they are still amateur quality dancers. A reason for this is that so often articles come out in magazines suggesting this dance form is "appropriate for women of all shapes and sizes." Oh really? Since when is it different from any other dance form in this regard? Any woman who wants to dance should dance, regardless of the genre. But not every woman who dances for the love of it should present herself in public as a professional when she is not.

For the record, bellydance does have wonderful ab toning benefits ... probably more so than most other dance forms, in that proper training isolates the upper and lower abs uniquely during dance technique drills. But toning the abs and losing fat from the abs = two different goals. Proper diet and aerobic activity are necessary to SEE your results, just as is the case for any other fitness regimen.

All of what I've stated above is about bellydance in America ... if you're looking to include dancers in the Middle East into the question, it's a bit of a different look at things. In the cultures that gave rise to bellydance, it was NOT for stage performance; rather, it was/is a form of folk dance ... not something people trained hard to perfect, but rather a way of dancing in more of a social festive context.

Video below is Rachel Brice, widely noted as the most popular and influential contemporary American professional bellydancer. Pure muscle!

Actually, regardless of the dancers outward appearance, most belly dancers have extremely strong abs! A lot of the movements/ab isolations that are employed by the dancers give the dancers belly the soft, almost slack look. They have the traditional "six pack"..its just that the "plastic thing in the middle that holds the cans together" is extremely flexible, allowing the dancer to roll and shift the 'cans" independently. It is all in the way the muscles are trained. This is what makes their abs look smooth, however, they are really quite powerful! A lot of women today who start an ab training regimen actually try to shoot for that look, then maintain it, without getting too "cut"..

Historically only married women who have had children were allowed to show their tummies. So traditionally the thin, tone, smaller tummies of the younger women were never seen.

In modern belly dance, the tradition of the "mommy tummy" is preserved through traditional dancers seeking to preserve the art. It appeals to the non-professional dancer (homemakers, housewives, older women) because it is the only dance style that incorporates and encourages a "real woman's shape" as part of the style.

Learning to do many of the moves requires great muscle tone and coordination. A modern belly dancer trying to reduce her natural shape to be that of a thin, tone, low fat version, doesn't use belly dance as their sole form of exercise because the moves used in the dance don't target specific areas for weight loss. It's worth noting that the shimmy of the skin on a woman with some meat on her bones is far more functional in the dance than a thin, tight, low-fat version is. And to a traditional/discerning audience, far more attractive.