Thats an excellent goal. If it seems big, try turning each month into a 30 day trial of goals that will get you there. For instance, the first month you may stop eating sugar, next month you may start walking a mile...etc. Because not only does it take time anyway, staging it will keep your body and mind from going into shock. The time will pass. I started PD in June, and I have lost about 10 pounds, and thats just from cutting out soda, fast food and eating better.