The former Spice Girls singer ate a lot while she was expecting her daughter Madison - who is now three months old - but has been losing her baby weight at a rapid rate, dropping to 147lbs from 165lbs by planning her meals and eating healthily on the Jenny Craig diet program.
Mel – who is married to Stephen Belafonte - told Britain's OK! magazine: "I really allowed myself the chance to pig out during this pregnancy, so I've got a bit of weight to lose. I was eating morning, noon and night, I was a house.
"The wonderful thing about this eating plan is it is all portion controlled and calorie counted, so I don't have to think.
"I have to eat regularly, every two to three hours. Even though I'm tired I'm coping really well, if I keep eating well and combine it with cardio workouts three times a week, then it's a done deal."
Although the 36-year-old star – who also has two daughters, Phoenix, 12, and Angel Iris, four, from previous relationships – is committed to her diet regime, she admits she is still allowing herself the odd treat.
She added: "I do think if you crave something, you've got to eat that. I splurge on whatever I'm craving, either a cheeseburger or a traditional English roast on Sundays. I believe in listening to your body and being consistent, but balance it out the next day by eating salmon and vegetables."