From ediets.com

Health and Diet
It’s time to mingle. Holiday parties may pose a threat to staying on track! Here are a few tips from the American Dietetic Association to get you through and allow you to have fun! Don't go to a party hungry -- hunger leads to overeating. Drink some juice; eat a piece of fruit, or some crackers before leaving

Fitness
Are you packing – lunch, that is. If you wait until you're hungry before saying "What can I eat?" you are doomed from the start. Once you get hungry, you’ll eat anything! Pack your healthy meals in Tupperware and Ziploc bags, and carry them to work or school in a small cooler. Preparation is the key!