Did 'Biggest Loser' Rachel Frederickson lose too much weight?

"The Biggest Loser" crowned its latest champion on the season 15 finale -- and it all came down to Rachel Frederickson vs. David Brown.

Yep, 24-year-old Rachel lost an amazing 155 lbs. since starting the show. That's almost 60 percent of her body weight: she went from 260 lbs. to 105. But she gained $250,000 in prize money.

The 'Today' show blog notes Rachel's win was record-breaking -- she lost a higher percentage of weight than any other contestant in the history of the show.

And while fans were excited for her big win -- some bloggers were concerned that Rachel dropped too much weight. EW said she looked "skinny-skinny," even by Hollywood standards.

BuddyTV was concerned, too: "Rachel has been such an inspiration and athlete all season. As soon as she is revealed, I can't help but think she looks way too thin, right? I don't know ... she just seems to have taken her competitive nature way too far."

And E! found that at 5'4", Rachel was underweight. According to Weight Watchers, the healthy weight range for Rachel's height is between 117 lbs. and 146.