If cereal is your go-to breakfast, you may be lowering your energy levels before your day has even started.
Eating cereals that are high in sugar, and other simple carbohydrates like white bread that immediately break down into sugar, will lead to an instant spike in your blood sugar, according to Dr. Nancy Rahnama, an internist and clinical nutritionist.
"And anything that spikes is going to crash," Rahnama tells CNBC Make It.
"This high-end crash and burn throughout the day leads to fatigue, irritability, changes in the mood, headaches, hunger [and] cravings."
High-glycemic carbohydrates, also known as simple carbs, can affect how refreshed and alert you feel in the morning, too, if you eat them for breakfast, says Raphael Vallat, a postdoctoral researcher at the Center for Human Sleep Science at U.C.