According to Closer magazine the star's dedication extends to getting up at 4am to begin working out.
Three hour daily workouts seven days a week mean that the 38 year-old has lost 40lbs - at a rate of 10lbs a week - since having twins Max and Emme in Feburary.
She is understood to have put on almost 4 stone during the pregnancy.
Back in shape: J-Lo, seen left in New York last month, and right, while still pregnant in February. She is reportedly rising at 4am for three hour daily workouts which have seen her lose 40 pounds in four weeks
A source told Closer that Miss Lopez has hired a crack team of nutritionists and personal trainers dubbed her '120 lb team' which refers to her target weight of 8 stone 8lbs.
Her workouts consist of Pilates, a one hour cardio workout followed by an hour of weight training.
Despite embarking on such a gruelling schedule the 5ft 5 performer has limited her food intake to 1,400 calories a day and banned all carbohydrates.
Last week Miss Lopez announced that she plans to run a triathlon in the autumn. She said: "I want to make my babies proud."
Happy couple: Jennifer and husband Marc Anthony are thrilled with their twin babies Max and Emme, and look happy together as they stepped at the Rolling Stones premiere last month
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