If you bring you lunch to work, eat, and then walk outside for a few minutes or around your office. During your breaks at work or whenever you have extra time on your hand, do some stretching exercises. You can also do this when you wake up. You may feel more refreshed if you do this when you wake up. Take up a hobby.
Gardening is good exercise and burns up plenty of calories.
Any hobby that requires you to move around is a good exercise alternative. Cook more often. When you cook you have to left and carry many items from your cabinets or pantry. This is a good weight lifting exercise. Play with your kids.