Glassman explained on "The Early Show" Thursday, that the average person who's working out maybe three to four workouts a week, looking to lose weight, maintain weight loss, or improve overall health don't need to take in more calories - they just need to eat at the appropriate time.
At breakfast before your workout, Glassman said, you want to make sure that you get a snack about an hour before. She recommended a 150- to 200-calorie snack of high calorie carbohydrates and proteins.
If you decide to work out in late morning, she said, oatmeal with some nuts is a great choice that combines carbohydrates and protein.
"You don't want to get too much fat or fiber because that can cause your stomach to be upset. That's not good for the guys on their bikes either."
Next a snack, such as a banana and peanut butter, are good choices for eating right before you exercise, according to Glassman.
If you're working out late afternoon, she said a simple turkey sandwich is a good choice for getting carbohydrates and protein.
If you're like Glassman, however, who rolls out of bed in the morning, she says you have to have something quick, such as coffee with skim milk -- or what she calls a "broken down" snack, such as a smoothie.
"Think of that blender as having churned up the food like your stomach would. It's easier to digest, and it won't make your stomach upset," she said. "You can make it the night before and get right on that bike."
During exercise, Glassman said there's no reason to get any calories from food or drink.
"If you're going longer than an hour, you do want to think about fueling yourself with quick-acting carbohydrates," she said.
Glassman said a handful of jelly beans, a portion of a sports drink or an energy bar, are some smart choices.
She said, "You don't necessarily need the whole (drink or energy bar)."
Water is also important for your workout, according to Glassman. She suggested drinking 20 ounces of water an hour before you work out. And during your workout, she recommended four to eight ounces every 20 minutes.
And she shared a secret: Gulp your water.
"When you gulp your water," she said, "it empties from your stomach a little faster, reducing your chances of cramping."
After your workout -- within 30 minutes of exercising -- you want to consume carbohydrates, protein, and antioxidants, she said to refuel you and replenish your body.
And how much exercise should you do a day?
Glassman said, citing United States Department of Agriculture guidelines, 60 minutes every day is recommended.
For more information on healthful eating and exercise, check out the Mayo Clinic's information on Timing and Exercise and Fitness.gov.