This cuts down on your stored energy especially if you are working out longer than 30 minutes. You will have to burn your muscle as an alternative fuel source. Decrease in muscle mass (not actually rippling in the mirror) causes a decrease in metabolism
Complex carbohydrates will give you energy and help you build muscle. On the other hand, foods high in sugar, such as pastry, give you a surge of energy that will quickly be depleted, potentially causing burn out. And a big breakfast of eggs and bacon will channel a lot of energy toward digestion--energy that you could be using to power through reps.
MY FAVORITE Breakfast is always egg whites & oatmeal....the oatmeal stays with me though out my training
But not everyone works out first thing the morning. If you rally later in the day make sure you have atleast an hour after your meal pre gym sesh. Who wants to exercise on a full stomach? NOT I........if you do, you will be working on digesting the entire time! Last time i checked, that was not the purpose of the gym.....take a walk
if you are coming form the office
or are too far out from a meal
grab one of these lil fueling snacks
they will keep you going