We have all seen the commercials and the tabloids about how the stars lose weight or how they need to. But what about the people who work with them. Nick watt has the skinny. ♪ Reporter:... See More
We have all seen the commercials and the tabloids about how the stars lose weight or how they need to. But what about the people who work with them. Nick watt has the skinny. ♪ Reporter: Kathy griffin is 54 years of age and loves nothing more than a skimpy two-piece. I'm a bikini model, nick. I don't know what you call your job. But I'm a professional bikini model who does some comedy on the side. Reporter: I mean, well, the pictures are great. Whether stalking the stage at the gladd awards or poolside with paris on her reality show "my life on the d-list," kathy leaves little to the imagination. Now meet tiffany, kathy's long-suffering assistant. Kathy griffin's office. You never worn aby keenny? Nuh-uh. I've been heavy my whole life. Reporter: This is a hollywood story, starring painfully skinny celebrities. I have to be thin because I'm on tv. Reporter: And their slightly heavier sidekicks, inspired by the boss to shape up. That's motivation right there, seeing her in her cute bathing suits. Reporter: But if you think she's gained five pounds, do you tell her? I fire her. Reporter: This if tiffany before and after. You've lost almost kathy's entire weight? I've lost an olson twin, i like to say. They're about 80 pounds, right? Reporter: She's being modest. Tiffany dropped nearly 90 pounds. Once more, before, after. And the boss puts tiffany's marvelous metamorphosis down to healthy eating, exercise -- she'd kick your ass, nick. Reporter: -- And the power of television. She is on the "kathy" show every week. Tiffany, is here. And let me tell you, when they do the camera shot of her in the front row in the adorable dress, that's maybe a little bit more of a motivator than she wants to admit. Reporter: Admit it? Is it? It is. I mean, when I started working for her, along came a reality show. Take your pants off and just wait for her. I didn't think anything of it. And then, once the show started airing and I started watching it, and I'm like, wow, I'm fat. And I need to do something about it. Reporter: Tiffany lost it slow and gradual, becoming a storyline on griffin's reality show and her talk show. I think you can have anything as long as the portions are -- I think that's the problem with this country. Yeah, portion sizes are crazy. It's too generous. Here we go. Did you actually start that question with, "i think that's the problem with this country"? How soon can youet on that -- plane to tulsa. Reporter: John lloyd taylor also knows the life of the chubby celebrity sidekick. For the last seven years, he's played guitar for those hunky young chaps the jonas brothers. That's him performing with the band on "good morning america." ♪ at his peak, john tipped the scales at a whopping 360 pounds. We made a 3-d movie at one point in the jonas brothers' career. It's 3-d, and I'm this huge guy in 3-d. And I'm thinking to myself, "i'm gonna look like a monster in this movie. I'm gonna be scary. Kids are gonna cry in the movie theater when they see me." Reporter: John just lost nearly half his body weight with the help and inspiration of his buff buddy joe jonas. It's like, "this guy could have any girl he wants." It's like, "maybe I should lose, you know, think about losing 150 pounds." Reporter: A bona fide food addict, john fell foul of life on the road. The touring industry is set up for you just to balloon. You're also eating, you know, a whole pizza when you get on the bus. Reporter: And then there's room service. Mulling over myself with the phone in the hand. And looking in the mirror in the bathroom, don't order the food. And then ordering a cheese burger and fries and like chicken wings. And then being like, "should i call back and cancel my order?" And this insanity plays out for 30 minutes. Reporter: These guys are, you know, heartthrobs. Does that make it harder for you, fat guy standing in the background? Yeah, for sure. I'm backing up this enormous group that's everywhere at the time, and I'm this huge entity in the back. Reporter: Joe gently encouraged john to work out, eat right and just get healthy. A vegetable platter's not very rock 'n' roll. Reporter: No, not so rock 'n' roll. Not at all. But feeling good and looking good on stage is. Reporter: And there's a new pre-gig ritual. Joe's alwaying push-ups and encoureverybody else. Reporter: You and joe doing push-ups before you go on stage? Before we go on. Reporter: John was so ripped, he was about to run a marathon. Then he broke his foot. But there's even bigger news. You're getting married? I am getting married. I saw her corner of the roomd I walked right up to her and introduced myself. Reporter: And you would never have done that? No way. My friends would have been like, "why don't you go talk to her?" I'd be like, "no, it's cool. I'm gonna go eat this birthday cake." It never would have happened. Reporter: It's a similar tale for nick feitel, who once tried and failed to land the gig of bethenny frankel's assistant on her reality show "bethenny getting married." Napoleon dynamite walks in here. And I'm like, has he met a brush. But ended up working for her anyway. And it changed his life. You've had a man-formation. A man-formation. Yes. Yeah, I've had one of those. Reporter: He lost his unibrow, got into yoga and wound up dropping 65 pounds at the svelte feet of ms. Frankel. I am more successful, generally speaking, with women. Yeah, you got a little game. Reporter: Now back to tiffany, who has moved out from the griffin shadow and is dating. It's not easy. And we're around fabulous gays all the time. But straight guys are hard to find one. Good ones. Reporter: I imagine a younger, straight guy, when he finds out you work for kathy, might get a bit freaked out and bolt? How did this interview turn from women's health into I'm a nightmare, nick? Nick? Reporter: I can't help but think I'd like kathy more if she wasn't so dammed hungry. If I ate more, I would be less funny. But happier. But I don't really care about being happy. I just wanna be funny. That's our motto at team griffin. Being mean and thin.
This transcript has been automatically generated and may not be 100% accurate.