Richard Foster on Fasting

"Some have exalted religious fasting beyond all Scripture and reason; and others have utterly disregarded it."
John Wesley

"Perhaps in our affluent society fasting involves a far larger sacrifice than the giving of money."
Celebration Of Discipline, Richard Foster, p66

"More than any other Discipline, fasting reveals the things that controls us. This is a wonderful benefit to the true disciple who longs to be transformed into the image of Christ. We cover up what is inside us with food and other good things, but in fasting these things surface. If pride controls us, it will be revealed almost immediately. David writes, 'I humbled my soul with fasting' (Ps. 69:10). Anger, bitterness, jealousy, strife, fear — if they are within us, they will surface during fasting."
Celebration Of Discipline, Richard Foster, p67

"Fasting helps us keep our balance in life. How easily we begin to allow nonessentials to take precedence in our lives. How quickly we crave things we do not need until we are enslaved by them ... Our human cravings and desires are like rivers that tend to overflow their banks; fasting helps keep them in proper channels. 'I pommel my body and subdue it,' says Paul (1 Cor. 9:27)."
Celebration Of Discipline, Richard Foster, p68

A Thought on Fasting

I've always thought that fasting was purely to show God you're serious about some particular matter, and to free up time cooking and eating meals. I'm sure this is all true, but it also appears there are numerous health benefits –  basically a rest and a revamp for your digestive system, cleansing out the toxic substances stored in the body. It can reset your body clock, give your body extra energy for healing and restoring itself. Interestingly, it can also increase your mental clarity.

According to www.howtobefit.com "it's a great tactic for mental and spiritual rejuvenation because it forces focus on important thoughts and frees the mind from everyday clutter. When you are deprived of nutrients, your body – in survival mode – begins to focus on things of true importance."

So it could well be that some fasts (probably shorter ones) could give you a mental lift needed for prayer, making them sharper and more effective. It also reminds you that you're human, frail and temporary.