"Eating wholesome food offered first to the Divine, with one-fourth of the stomach kept empty, is mitahara or moderate eating." ~ Hatha Pradipika

Mitahara is the yogic concept of moderate eating.  The advice of author, journalist and food activist Michael Pollan pretty much sums it up - "Eat food.  Not too much.  Mostly plants."  It's a reminder to eat fresh, simple, wholesome foods, with a sense of gratitude, in amounts just enough to nourish the body with the fuel it needs, no more and no less.  In this way, our organs are released from the burden of processing our excesses.  The resulting freed-up energy can then be used for supporting good health as well as for yogic purpose of building and directing energies.  Mitahara primarily refers to food, but also refers to anything else that we take in through our senses.