You might think that pulling an all-nighter at the office will cut down your workload for the next day. Think again. There are plenty of reasons on why working overtime is actually bad for productivity. And it's mainly due to how your brain works.

Working When You're Tired Is Like Being Drunk
Research suggests that poor-quality sleep leads to fatigue, decreased alertness, and impaired cognitive performance. When you're tired upon waking, even super simple tasks like turning on a light switch can become complicated.

Energy Levels Usually Peak Mid-Morning & Early Evening
Our working memory, alertness, and concentration all improve with our body temperatures. This increases throughout the day, and especially during noon.

Our lung capacity also is also at its highest at around 5 p.m. which is necessary for boosting our mental capabilities. Therefore, it's best to tackle the really tough projects during the end of the day.

Your Brain Can Run Out Of Fuel
While office workers might think that their work is purely mental, but there's actually a lot of physical effort involved as well. 

Tim Ferriss, the author of the '4 Hour Work Week' recommends treating our workdays like how weightlifters treat their workouts: by creating a rhythm of intensity and rest. He explains:
When people think of mental activity, they tend to think of it as an ethereal zapping of electricity that has no cost to the body. That's not true, the brain is a massive blood and oxygen sink. You need stimulus and recovery in mental work in the same way that you need stimulus and recovery for sports.
So if you're typing away at your keyboard for eight hours or more without a break, your brain-muscles won't have enough time to recover in order to keep going. So be sure to take those quick breaks every now and then!