matter what time of day, exercise actually helps to increase the depth, or quality, of sleep, he said.

“Exercise in the evening does not disturb sleep and can even promote sleep a little bit,” said exercise science specialist Shawn Youngstedt, professor of nursing and innovation at Arizona State University, who’s in the third year of a four-year study of veterans with sleep apnea. “Exercise ending even a half-hour before bedtime does not disturb sleep for most subjects.”

It’s not so much when you exercise that affects sleep but perhaps how consistent you are with your wake time and your sleep time as well as with what you eat and when, Czeisler said.

The idea is to try to keep the interval between your first meal and your last meal of the day on the order of 12 hours or less, according to Czeisler. That means if you’re having breakfast at 8 a.m. you don’t want to eat dinner after 8 p.m.

In addition, eating a meal after your body begins to release the hormone melatonin, which happens after the sun sets and helps to maintain glucose levels during the night, he said, can interfere with your circadian rhythm, which ultimately has the greatest impact on your sleep.

And that’s where evening workouts can be tricky. To train optimally, a person who eats breakfast at 8 a.m. would need to finish running (and stretching) at least by 7:30 p.m. to finish eating at 8 p.m., with maybe a half-hour left before sunset.

Seem unrealistic?

Maybe.

I decided to try a seven-mile run after work, but before I left I checked what time the sun would be setting. It turned out sunset was about 8:30. So I ate breakfast later than usual that day, went to work and then ran, getting in just six miles before stopping at 8 p.m. I did a few quick stretches and ate some chicken and brown rice leftovers with roasted vegetables. I was in bed by 9:30.

I realize on some days it might not be possible to do everything right. I asked Youngstedt about this.

“People should exercise when it is convenient,” he said, “when they can consistently do it.”

“The three pillars of good health are nutrition, exercise and sleep,” Czeisler said. “But they shouldn’t be at odds with each other. Exercising at 4 o’clock in the morning and therefore not sleeping or getting up at 5 and losing two hours of sleep in order to exercise is a bad idea, just as eating in the middle of the night is a bad idea.”

In addition, long-distance running can increase your sleep needs, which can average between seven and nine hours, depending on your age, Czeisler said.

But just as you do when you travel across time zones, you can adapt your biological clock to your training. This is especially important to keep in mind about a week before your race so that you can adjust your rhythm to accommodate the race start time, he added.

Don’t know how much sleep is right for you? The National Sleep Foundation has guidelines at sleep.org.

According to Philadelphia sports dietetics specialist Kelly Jones, if you’re planning to exercise in the evening, it’s important to eat throughout the day to fuel your workout and to prevent overeating afterward.

Yet don’t be tempted to exercise and then go to sleep without eating, Jones said.

“The same fueling and recovery principles apply, no matter what time of day you are moving your body.”

Jones recommends a balanced breakfast and a midmorning snack, which would allow you to eat lunch later in the afternoon. You want lunch to be a slightly bigger meal than usual, she said, while staying away from fried foods and excessive saturated fats.

This way, a snack two hours prior to exercise can help you to fuel your workout and prevent excessive hunger.

After exercise, you want to consume a combination of carbohydrates and protein within an hour, she said.

This may require some planning and preparation, but in a pinch, Jones said, you can grab a cup of yogurt to mix with whole-grain cereal and fruit. Tart cherries added to yogurt and smoothies are great for muscle recovery and have potential sleep benefits, Jones noted.

Specific foods to avoid at night include anything with excessive sugar or any caffeine, Jones said.

It’s important to eat even if you’re going to sleep not only because you just exercised, but also because the growth hormone that is released after you fall asleep (which aids in muscle recovery) depends on protein and carbohydrates, Jones said.

She added that if you’re exercising for longer than an hour, even in the evening, you should consider fueling during the workout. Many popular sports gels and energy drinks contain caffeine, however, so check the label before consuming, she said. Czeisler noted that caffeine can stay in your system for up to nine hours. This means you could still experience the effects of about half the amount of caffeine from the cappuccino you drank at lunchtime as late as 9 p.m.