I lost track of time at the gym yesterday. After an hour of Bodyflow, I did a half hour of cardio, then upper body weights. Suddenly, I realized I had only 10 minutes to pick up my daughter from preschool. No worries, it all worked out and I didn't have to sacrifice building my lean body mass -- an important tool to prevent weight gain over the holidays.

Most of us throw consistent healthy eating out the window in December as easily as we toss down the second appletini. OK, fine, eat the gooey appetizers, spritz cookies and slosh it all down with a calorie-filled cocktail or two. But don't let temporary holiday insanity put a halt to your resistance training. Outside Magazine explains exactly why:

• Quantified, muscle burns 13 kcals/kg per day compared to 5 kcals/kg per day for fat. Even if you're not eating perfectly over the holidays, do not stop partying in the weight room.
• About 80 percent of your energy expenditure is due to body composition, while the things you can't control -- genetics, age and gender -- make up the rest. Building your lean body mass kicks Father Time and your DNA right in their fat guts.