"Eat light to be bright" is the old adage of a friend of ours - and it works! If you want to feel light and joyous throughout your day, eat light and sparing meals. Why does this work? Because food is a very heavy material substance that requires a great deal of energy to process and digest.
Food also brings you closer to the material world and further from the spiritual world (unless you follow very specific processes to raise the vibration of your food). So if you want to be closer to the world of spirit, which is lighter and more joyful than the world of the physical, eating light is a very simple way to get there.
Now, this doesn't mean you should go on a crash diet or deprive your body of necessary food. Rather, pay attention and be conscious as you eat. Your body (and your spirit) will tell you when you've had enough. Surprisingly enough, for most people the level of "enough" is often just half of what they normally eat. Give it a try!