Eat better food. Eat the right amount of it, at the right times. This isn't really something that can be answered, specifically, it's something you need to figure out yourself. When you eat X, how does it make you feel after 15 minutes? After an hour? After four hours? After a day? Keep answering those questions until you are only eating the foods that make you feel good at all of those points.
I'll give you a hint, and someone already posted it: water. Lots of it.
Also, don't lack exercise. You don't have to. There are lots of ways to stay active, even while you're working.
And don't work so much that you have to do these things while you work. There is lots of evidence that you are not being more productive by working these many more hours, and that kind of stress is far outside a healthy range, which can cause all manner of digestion problems.
In short, eat healthy food food, full of nutrients, which make you feel good for a significant period of time. Drink water. Do physical things. Work sane hours.
Oh, and sleep. Between seven and nine hours a day, every day, more or less around the same time each day.