According to the Mayo Clinic, strength training helps burn calories, reduce body fat, strengthen bones and increase stamina [source: Mayo Clinic]. And the good news is that you can use your own body weight to sneak in some strength training.
For example, according to Michael Roussell for Shape Up America!, you can try desk pushups. While standing, position yourself a few feet from your desk. Keep your feet together. Then, put your palms on the edge of your desk, about a shoulder width away from each other. Lower down to the edge of the desk, and push back to the starting position. As you increase your strength, see if you can do 15 reps in a row [source: Roussell].
Need another option? You can turn it around to work your triceps, as described by Courtney Myers for Forbes.com. Put your palms on the desk behind you. Again, keep your feet together. Start with your buttocks touching the desk, but then as you bend your elbows, come forward a bit. You are now in position. Dip down until your upper arms are parallel with the ground and then push back to the starting position [source: Myers].