Hi Tracey
I would disagree with Erratic. Over the last 2 years by modifying my diet to healthier options, Changing from 3 large meals a day to 6/7 smaller ones and taking up running I have lost over 3 stone and lost 8 inches off my waist, from a 36" waist to 28". Last time my waist was this size I was a teenager :)
You can't spot reduce body fat, so doing core exercises will not necessarily move fat from that area. Your body decides for itself where it will take fat from.
Tracey maybe worth having a look at your diet and making changes if necessary.
Good Luck.
MK