Take a brisk walk for 30 minutes during your lunch break and then take the remaining 30 minutes to eat. Adding exercise to your day will make you more alert for the afternoon and give you a better outlook on life. Make getting a walk a priority over spending that time on the phone or on the computer.
Whether you realize it or not, finding more time to exercise is not simply a matter of time, it is a matter of practice, thinking, and creativity as well. When you have the incentive, you will find the time.