The new Southpaw trailer last month featured Jake Gyllenhaal showing off an extremely toned torso. But according to his trainer, former professional boxer Terry Claybon, it took a huge amount of work to get the 34-year-old actor ripped for the shoot, including six months of training before filming even started. He also worked out for an incredible six hours per day, including 2,000 sit ups, 1,000 each morning and the same at night. Of course, Jake had to work even harder to get in shape because he had just  dropped approximately 30lbs to play freelance crime reporter Lou, who stumbles upon the dangerous underworld of Los Angeles in Nightcrawler. Scroll down for video . Blood, sweat and tears: According to his trainer, it took a huge amount of work to get Jake Gyllenhaal ripped for Southpaw, including six months of training before filming started, 2,000 sit ups and six hours of training each day . Much thinner: The 34-year-old lost 30 pounds for 2014 thriller Nightcrawler and had  to put that weight  back on plus 15lbs of muscle . He not only returned to his normal weight - but he then put on another 15 pounds of pure muscle to play the desperate fighter Billy Hope. His trainer Claybon told Yahoo: 'Gradually we built up, day-by-day, to 2,000. It takes time to do that', and revealed that his exercise regime included, 'three hours of boxing in the morning and three hours of strengthening, conditioning, and cardio at night.' Speaking about his weight loss for Nightcrawler, Jake told Us Weekly: 'I knew that [Lou] was literally and figuratively hungry, [so I got into the] mode where I was always a bit hungry. Beaten: The trailer shows a muscular Gyllenhaal bloodied and bruised by an opponent in the boxing ring . Bulking up: Jake poses here with his trainers, including former boxer Terry Claybon (second from right), who was responsible for whipping the once-scrawny actor into shape . Gyllenhaal also attended several boxing matches to watch how real fighters move in the ring . 'It's not different than getting into character for anything. It's more about believing where you are and being present where you are. Who's to say what the process is? I have a strange one … but I love what I do.' Claybon explained to Yahoo that Jake put back on the weight he had lost before gaining an extra 15 pounds of muscle for Southpaw. Health experts told the Daily Telegraph that Gyllenhaal likely went on a high-protein diet, that likely included protein powder. He likely had to consume 130 grams of protein - two and a half times the daily recommended intake. Health experts also told the Telegraph that such drastic body changes could cause long-term damage to his body. The huge swing in Gyllenhaal's physique recalls other drastic changes actors have made in their bodies. Among the most recent and most notable is Matthew McConaughey's turn from  Magic Mike hunk to Dallas Buyers Club AIDS patient. Meanwhile, in Southpaw, Jake plays Billy Hope, a professional boxer who must rebuild his life after his wife is killed and his daughter is taken away from him. The recent trailer opens with Gyllenhaal's understatement: 'I expected a hard fight. I put my family through a lot.' It then cuts to him in the ring bloodied and bruised as he takes a relentless pounding from an opponent, while his wife, played by Rachel McAdam and Curtis '50 Cent' Jackson look on in horror, before Hope suddenly turns it around sends the other boxer to the canvass. Horrified: His wife, played by Rachel McAdam and Curtis '50 Cent' Jackson can only stand by and watch ringside . Adrenelin: Gyllenhaal plays Billy Hope, a boxer who allows himself take punches to fire himself up . The reason Gyllenhaal's character allowed himself to take the beating in the first place is then explained. 'The more you get hit the harder you fight, I get it,' his wife says. 'Only now you've taken way to many hits before you get off. You cant fight like that any more. Think about her.' She's talking about the couple's only daughter Leila, who is played by film newcomer Oona Laurence. The youngster is fresh from lauded performances on Broadway as Matilda in the stage adaptation of the Roald Dahl classic. But the trailer also reveals there's a much more devastating blow in store for Hope, when his wife is accidentally shot dead by a bodyguard during an altercation with he has with another boxer who had been taunting him, which McAdam's character had told him to walk away from. Doomed: The two-and-a-half minute clip reveals McAdams is killed during an altercation between Hope and another boxer . Hopeless: The boxer must fight to regain his daughter, who is taken from him by child services following the death of his wife . Young star: Leila Hope is played by Oona Laurence who just wowed audiences on Broadway as Matilda . And things get worse for the embattled boxer as the child protection services take his daughter away from him after he falls into a dangerous cycle of self destruction following the death of the child's mother. The film also stars Rita Ora, who recently played Christian Grey's sister in Fifty Shades Of Grey, as well as Forest Whitaker and Naoime Harris, replacing Lupita Nyong'o who dropped out in August. Shot: McAdams plays Maureen, whose death starts Gyllenhaal's downward spiral . The real Jake Gyllenhaal: When not packing on muscle or dropping weight for a role, Jake looks like this (pictured in January)
Gyllenhaal lost 30lbs for thriller Nightcrawler then gained it all back - and put on 15 more pounds of pure muscle in six months .
Went to the gym twice a day for six hours .
Regime included 2,000 situps, three hours of boxing and three hours of cardio and weight training .
Mimics great Hollywood physique changes like Matthew McConaughey going from Magic Mike hunk to Dallas Buyers Club AIDS patient .