No matter you are perfectly fit or a little on the heavier side, you might end up a little heavier after the holidays. We just cannot help it. Celebrating is equivalent to eating for all our lives. Is there a Fengshui way to prevent it? Unfortunately the only person that can prevent you from over eating is yourself. However, drink some 'contented water' might help. 
First, select an octagonal or pentagonal clear drinking glass. If you don't have one, there is no need to rush out and buy one. A regular cylinder glass will be OK. No one has tried paper cups or foam cups yet. So if you use either of them, please make sure to let us know if it worked.
Second, calculate your content direction and locate it. Fill 5/6 of your glass with drinking water. Please use plain drinking water only, not soda, juice, wine, milk, eggnog, coffee,  tea or any type of flavored, colored, or carbonated water. Take your glass with you and stand (or sit) facing your content direction and slowly count to 64. Then drink the water completely. This should help your stomach feel contented for a while. 
This can be repeated if needed. 

Some extra pointers for parties: you don't have to be standing alone while you are counting. Pretend that you are listening. Smile and nod then drink off your water slowly after you count to 64. You will look like a great listener.