In an interview with Marie Claire, the Back-Up Plan star explained that having a target to aim for is a good way to keep motivated.
She said: "One of the good tricks is to have a goal - for me it may be getting in shape for a video shoot.
"The other is portion control. I love to eat everything and you pretty much can - a little piece of something fattening is not going to kill you. It's when you eat the whole box that it's going to kill you."
According to the 41-year-old mother of twins, not eating until you are full is a good way to control weight.
Lopez confirmed she was pregnant in November 2007 during her En Concierto tour and the Holloywood superstar gave birth to twins Emme Maribel Muniz, and Maximilian David Muniz on February 22nd, 2008.
