Lopez, 39, who gained 3st 5lb with twins Max and Emme signed up for triathlon, which involves swimming, cycling and running Her workouts change daily, depending on the day, the time and the freedom," said her trainer Gunnar Peterson, who also works with Penelope Cruz.
She started out with light workouts including light cardio and body-weight exercises. She also banned junk food from the house to avoid temptation.
New mums eager to loose the baby bulge can make it work with triathlon but keeping it small with a 5K run/walk .
Nutritionist Carina Norris said that banning treats from cupboards is a good idea
"If you don't have sugary foods in, you can't eat them," the Mirror quoted her, as saying.
"Don't let your partner have them in the house either!" she added.
Halle Berry also opted for three cardio sessions such as jogging, swimming and cycling, two circuit sessions with light hand weights and one core session (core muscles help keep your stomach flat. Exercises usually involve sit-ups and crunches).
She started having plenty of lean proteins such as skinless chicken and lean red meat, complex carbs, such as brown bread and rice, and a vegetable, drank lots of water, and shuns coffee and tea.
"A good mix of complex carbs, lean protein, fruit and veg will keep Halle healthy and energised," said Norris.
"Avoiding tea and coffee is also good as too much caffeine can disrupt sleep though a cup or two a day won't do any harm," she added.
Nicole Kidman opted for several hours of dance rehearsals a day and her weight dropped off.
Several hours' exercise a day is too much for most of us but the odd dance class would help regain your shape.
Jessica Alba says that she lost her tummy by breastfeeding but has also started gentle workouts with her personal trainer Ramona Braganza. She has also ditched fried foods.
Breastfeeding burns up to 500 calories a day and has health benefits for the baby, too.
"Fried, fatty foods can lead to low moods and make you sluggish and tired," said Norris.