AN INTIMATE ALL-ACCESS LOOK AT THE JONAS BROTHERS, PLUS A BARBARA WALTERS EXCLUSIVE: CARLA BRUNI-SARKOZY, THE FIRST LADY OF FRANCE, ON "20/20" FRIDAY, AUGUST 1

The Jonas Brothers give "20/20" viewers an all-access pass with an intimate look inside their tour bus and their daily life on the road as they promote their new CD, "A Little Bit Longer." Nick, 15, Joe, 18 and Kevin, 20, get personal with ABC News correspondent Juju Chang, discussing their music, rumored romances and the illness that nearly sidelined the band. The in-depth report on one of the hottest bands of the summer airs on "20/20" on FRIDAY, AUGUST 1, from 10:00-11:00 p.m., ET, on the ABC Television Network.

Then, a Barbara Walters exclusive: In her first American interview, Carla Bruni-Sarkozy speaks candidly to Walters about how she reconciles life as First Lady of France with a successful career as a recording artist, the provocative lyrics in her new album, "Comme si de rien n'�tait" ("As If Nothing Happened"), which is No. 1 in France, and her surprising whirlwind romance and marriage to the President of France, Nicolas Sarkozy. During the interview, which took place in Paris, Bruni-Sarkozy also discusses her controversial past, including rumored high-profile affairs with such rock stars as Mick Jagger and Eric Clapton.

And: Imagine being able to eat cake, pizza or steak and still lose weight. It may sound too good to be true but, according to the a diet aid "Sensa," by sprinkling food with flavored flakes, people's extra pounds will disappear because a person will feel full faster and stop eating. The marketers of "Sensa" say it's a scientific breakthrough, but "20/20" interviews experts who say this breakthrough has yet to be proven. Jim Avila reports.

Plus: Most Americans spend about eight hours a day sitting behind a desk. Obesity expert Dr. Jim Levine says sitting on our bottoms at work is making us fatter and less healthy than ever before. "20/20" gets exclusive access inside Dr. Levine's ultimate office makeover and reports on a six month Mayo Clinic study to see if getting people up on their feet and moving could help workers lose weight. Deborah Roberts reports.

"20/20" is anchored by Elizabeth Vargas and John Stossel. David Sloan is executive producer.

David Sloan is the executive producer.