tonight on "nightline" fit to be fat. hollywood is slowly embracing a curvier crowd. but the ordinary and overweight hardly mainstream. we follow one man's quest to lose it big. a girl and her gun. the ad says just the sight of this big bad pistol is enough to scare an intruder unconscious. but tonight, the real story of how glock became america's gun. and tonight, we are in brazil on the search for the jaguar. an invisible cat with skull-cracking jaws. and we'll meet the men who devote their lives to finding these elusive beasts. >> keep it right here,

happy friday, all.

if you try to lose those 10, 20, 30 pounds, what provides stronger motivation? modelled bodys as a line of your finish line? or does a look of like-bodied strivers help you focus on the goal. tonight we focus on the new kind of gym where all the members have a the latter in common and they know what it's like. alec perez. >> reporter: in a culture that values thin, the debate is on fire. from plus-sized models posing for the cameras to sur voracious superstars like adele, belting it out and winning an oscar for "skyfall." plus size is going mainstream with clothing stores that market cute clothes to big girls. >> i think in today's world, when there's so many positive role models out there, octavia

spencer, adele, melissa mccarthy from "graibridesmaids." kate upton is a swimsuit model famous for her curves. is there still real shape in being overweight? to chris, sharon, luis and david, the answer is yes. they are all here at down size fitness. >> 15 seconds. >> reporter: a chicago gym where membership is reserved for the overweight only. >> there's a need for a place where heavy people can go and concentrate on losing weight. >> reporter: they are all self-described outcasts from the mainstream gym scene. >> there's not a culture of acceptance in america for overweight people. you can still discriminate based on size. >> reporter: down size fitness is now part of the national argument. are overweight people still treated differently? just this week, the cvs pharmacy

chain told workers they had to submit information on their weight, body fat and glucose levels or pay a sur charge. and extra $6 h00 a year for the company's health insurance. another hot button issues -- overweight airline passengers. should they have to buy an extra seat? one blogger said she was humiliated by a southwest airlines gate agent in 2011. >> the gate agent came up to me and he began -- he asked me how much i weighed. he said that i was too fat to fly, that i would need an additional seat. >> reporter: sharon has also felt the pain of harsh stares and ridicule. she joined down size fitness last year. starting weight, 376, and still reeling from the sting of a bad experience with a personal trainer at a mainstream gym. >> i don't know if he was afraid of, you know, training a fat

person or what it was, but all i was able to do is sit in the corner and work on the treadmill. it made me feel like a pariah. i didn't belong there, but yet i was allowed to join. >> reporter: since joining down size fitness, she's lost 20 pounds. >> we ask people to come five times a week. we call people if they don't show up. >> reporter: they only allow membership to those at least 50 pounds overweight. >> yeah, you're segregating the obese people. why do they need to have their own gym? how do you respond to that? >> reporter: gym . >> gyms people are built for fit people to stay fit. i don't think they're built for fat people to get fit. we're segregating for a reason. >> reporter: her goal weight -- 225. luis also joined just six months ago. starting weight, 310 pounds. >> you got it. >> reporter: he tried to lose weight at one of those other gyms and was a member for 12 years, paying $75 a month.

but after only one year, he never went back. so for 11 years you paid for a gym membership you never went. >> it wasn't something i was comfortable going into the gym. you're on your own. there's no one there to help you. there's no one to explain what you should be doing. >> reporter: so far, luis has lost 50 pounds. his goal weight -- 180. >> you do a lot of soy. >> this exercise physiologist says the program works. is this a copout in some way? and when does it end? do you start having grocery store s for bigger people? planes for bigger people? >> this is about making someone to feel comfortable to make the chan change, to engage in healthy behavior. it's not oh, okay it's okay that that you're overweight. you can stay the way they are.

>> david has lost 202 pounds and hopes to get 190. chris took me back to his neighborhood and we traced the half block walk that eventually brought him to down size. >> my back was just hurting too much. >> reporter: now he's one of the most active members at the gym. full disclosure -- this is a battle i'm all too familiar with. when i was a teenager, i weighed 356 pounds, a size 54 waist. it took me years of dieting and exercising alone before i was able to bring down my weight and live healthier. having others who understand the frustration of being obese would have helped. >> there's definite success here. people are losing a lot of weight here, and it's a great place to do it. i'm alex perez in chicago. >> i had no idea alex lost that much. congrats. and thanks for the piece. coming up next, how america fell

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they say that you can bury a glock pistol in the dirt, dig it up a year later and it will fire just like new. but even more durable is the love many americans carry for this particular brand of gun. it's been 98 day since the sandy

hook massacre reignited a fundamental debate on personal fire power. and in that time, gun control advocates have seen their hope for change smashed against that ever lasting weaponry. to help understand how it got that way, it helps to understand the rise of the glock. attractive girl in tight pajamas settles in for a cozy night. but cue the creepy music. a scary man is lurking outside. she grabs her glock semiautomatic handgun and the tension builds. now in the real world one study found that women living with a gun are almost three times more likely to be shot to death. and in 2010, 16 times more women were killed by men they knew than by strangers. but in a world according to glock, just the sight of their fearsome weapon is enough to

roll the invading stranger's eyes back in his head without even firing a shot. >> somebody picked the wrong girl. >> this ad has been viewed hundreds of thousands of times online to mostly rave reviews among youtube commenters. but in reality, they don't need to post these. they're already america's so-called super gun. good guys and bad, on screen and off. >> between your faith and my glock .9 millimeter, i take my glock. >> it gets the approval of arnold in "end of days" and tommy lee jones in "u.s. marshals." >> do you have a backup weapon? >> never had a need. >> get yourself a glock and get rid of that sissy pistol. >> congressgabby giffords was

not only shot with one, he still carries one. >> and it's standard issue of the fbi and around 65% of american cops. what colt and remmington were to america's wild west, glock is to this country's violent present. and that's amazing since it's only around 30 years old and comes from europe. but its rise is a stark lesson in just how difficult any form of gun control could be going forward. it all begins in the 80s, in the suburbs of vienna when a guy named gaston glock decided to move from making knives and curtain rods to making guns for the austrian army. he had never made a pistol before, so he asked expert shooters what they wanted and came up with a game-changing design. but using mostly composite plastic instead of steal, glock created a weapon that's light and tough with a very easy trigger pull and no cumbersome

thumb activated safety. it could shoot 17 bullets, almost three times more than the typical revolver as fast as you could pull the trigger. and glock made the brilliant decision to first offer them to police departments. just when the crack cocaine wars were heating up and cops felt vulnerable. another group that showed early interest, hollywood prop masters who loved the futuristic look. as paul barrett writes in his book, "glock -- the rise of america's gun" shootouts on the set of "law & order" were featuring this austrian import. >> some of the american companies will want to know will our guns be in the hands of good guys or bad guys. glock just said go ahead and put it in the movie. we don't care. >> that's a porcelain gun made in germany. it costs more than you make in a month. >> almost every part of that speech in "die hard 2" is

factually wrong, but when there were fears that an undetectable gun could show up in america, sales skyrocketed. barrett said glock saw an opportunity. >> when the law was enacted, it was enacted with a grandfather clause, meaning everything that existed before the day of enactment was still illegal. this left glock with a huge supply of prebanned equipment that was still legal to sell, which the company then dribbled out over time. and the dark glamour of the glock, you know, went up. because gun aficionados resented the resfrings that's the gun they don't want me to have, i want two of them. >> thanks to a perfectly legal trade-in program, glock is able to resell used police guns. >> a lot of departments are cash strapped, you know, looking for

money. it is a way of ensuring that their officers are equipped with the best and latest tools of the trade. >> reporter: in a statement, glock points out allowing law enforcement agencies to trade in firearms for the purchase of new duty weapons is a standard practice by all major firing arms manufacturers. >> but you have to think there's a possibility that a cop could have his old glock pointed at him at some point. >> exactly. that's why i've never been in favor of that type of program. but often times it's not even us. it's the chief of police. >> bratton thinks banning buy-back programs would be a political impossibility and just the talk of another slaughter, tougher laws, puts more guns into circulation. so whichever way the political winds blow, glock has proved that it's always a good time to be in the gun business. >> and coming up next, jaguar hunters. we'll venture into the wild for a look at one of the most

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the harpoon hunt for a white wa wa whale, stuff of novels, but the modern day is the search for the jaguar. these explorers soldier on. >> jaguars are so elusive that locals here call them phantom

cats, but they are really 200-pound nightmares. jaws strong enough to crack a skull like an egg shell. scenes like this of the jaguar hunting and devouring the world's biggest rodent at about 150 pounds are almost never captured except here in in brazil's new york state-sized wetlands. which might explain why during our visit there, not one but two filmmakers are on assignment for "national geographic" both of them hoping to eare veal the secrets of brazil's top predator. first, christian balmeister, the stoic german photographer who thinks patience is the key to getting that never before seen shot. >> in the moment the action takes place, everything is very fast. so you have to react very fast and be in the right place at the right time and do the right thing, which is very hard to do. >> and there is lawrence

warbaugh, a tattooed and local native who says the local touch ensures he's close but not too close to the phantom cat. and although he's captured some very private jaguar behavior, christian has captured this unprecedented sequence of a jagu jaguar. so we throw our lot in with the german giant, leaving lawrence behind. but there's barely enough room on the tiny boat for christian, much less me, because as we quickly discover -- look at that thing. oh, my gosh. the 6'5" german has proportionally sized equipment. after confessing to a slight case of camera envy, we move on. christian says he knows a prime

spot for jaguar spotting. off the beaten track. so while lawrence plies the main river, christian leads us down ever narrowing tribu ining trib. >> we heard there's a jaguar upriver. it's ten minutes away. if we're lucky, we'll make it. >> hope we don't get stuck. and with those words, we get really stuck. kind of hard to get footing, huh? >> how's the water? >> nice. a couple of crocs in here. i'm sinking up to my hips. it takes almost an hour to get out. we race to the spot and it pays off. wow, it's big. >> oh, yeah, yeah. >> reporter: virtually camouflaged, we capture only the briefest of glimpses. to. >> we scramble up a little cliff to get a better view, but by

then he's already gone. >> he's going deeper into the bush. >> reporter: as the sun sets, we begin the slow chug home. but christian seems to have already reconciled with their strikeout. >> at some point, of course, you're asking yourself, what are you doing with your life? spending days and days and days on a river and far away from home. it's hard, yeah. >> reporter: and out of nowhere, another boat brushes aside us. it was our friend, lawrence. mischievously he shows us that video from just a few hours before. >> so sorry, matt. i told you i'm the jaguar guy. i'm sorry. i'm brazilian. who knew some of the world's greatest wild life photographers who spend months silently waiting for a single sequence can talk so much trash. >> gorgeous. "the phantom cat" premiers this

sunday march 24 on nat geo wild. our peeps at "gma weekend" will be working while you rest. and please, have a fantastic weekend.