If you think working overtime, skipping your lunch hour and staying chained to your desk will make you more productive, you need to cut yourself some slack and take a break.
Staring at a computer screen for more than 2 hours per day can cause Computer Vision Syndrome, a real affliction, which causes blurry vision, headaches, dry eyes and can lead to long-term nearsightedness. However, getting up and away from your desk for just 5 minutes can alleviate eye strain and reduce fatigue in addition to making you feel better. The mere act of standing at your desk instead of sitting at it can help you burn up to 2500 calories per week. Not bad for just standing around.