We're a nation obsessed with thinness (yet ironically obese) and celebrity weight wars are a favorite fixation. When an actress slims down too much, we race to label her anorexic, but God forbid she gains five pounds or we'll take a picture of her bottom and magnify her cellulite on the cover of a magazine.

The following five women know the cover of a tabloid all too well, and the accompanying headline usually reads something like, "Actress Packs on Pounds" or "Starlet Suddenly Skinny."

We're not talking about celebrities who pack on the pounds or whittle their waistlines for a movie role but about those who (despite fame and fortune) just can't seem to keep their weight in check.

Think you've heard it all when it comes to celebrity weight wars? Read on for our top five celebrity yo-yo dieters ...

Jennifer Love Hewitt

No. 5: Jennifer Love Hewitt

OK, so this lovely actress was never really that big, but her weight wars have certainly been public nonetheless.

In her youth, Love was the celebrity that every girl wanted to be and every guy wanted to be with. She managed to keep a slim (albeit curvy) figure over the years, but more recent less-than-flattering tabloid photos of Love in her swimsuit revealed that this "Ghost Whisperer" had become more than pleasantly plump.

In response, Love claimed to be proud of her curves, but (not surprisingly) the unflattering photos were followed a few months later by a cover shot in which she had nixed the flab (with a headline that promised to divulge how she'd lost 20 pounds).

While she's not the first celeb to fluctuate in weight, with that naturally curvy frame, we wouldn't be surprised if Love continues to struggle with the scale.

Janet Jackson Super Bowl halftime blurb

No. 4: Janet Jackson

Her late brother may have been the king of pop, but Janet Jackson is the undisputed queen of yo-yo dieting.

Despite a successful career, this pop star/actress has had her ups and downs (on the scale that is). One minute she's sporting rock-hard abs on tour and the next day her frumpalicious frame is consuming the cover of a tabloid. A plus-size Janet even appeared on the big screen in the 1996 comedy "The Nutty Professor."

According to interviews, Jackson has struggled with her weight since age 10, when television producers asked her to drop pounds for a role. More recently, Janet packed on the pounds for a movie role (supposedly), but the project fell through.

Amazingly, Janet always manages to drop the weight (reportedly thanks to a strict diet of lean protein and veggies), but she doesn't seem to know how to keep it off.

Carnie Wilson 2007 file photo

No. 3: Carnie Wilson

Carnie Wilson has made a career out of being a fat celebrity. Since her initial fame and fortune as part of the 1980s rock trio Wilson Phillips, Carnie has been best known for her struggles with the scale.

In 1999, Carnie topped the scale at more than 300 pounds before undergoing a very public gastric bypass surgery. An initial success (she lost more than 150 pounds), Carnie's weight has fluctuated ever since, exacerbated by two pregnancies. In 2006, she joined the cast of "Celebrity Fit Club" and shed some pounds, but the diet didn't stick and she's now eating her way back to her presurgery weight.