No Time to Exercise

I need to maximize my workouts. Do I burn more calories by exercising in the morning or at night?

By Martica Heaner, M.A., M.Ed., for MSN Health & Fitness

Q: I'm so busy that when I can make the time to fit in a workout, I have to get the most out of it. Is it better to work out in the morning or evening? I've heard that you can lose more weight working out earlier, because you elevate your metabolism and burn more calories all day. But I've also heard that if you exercise at night, the body burns more of the calories that you ate during the day. Can you please clarify?

A: If your primary goal is to burn more calories, then what's most important is doing as much as cardio as you can, any time you can fit it in—night or day. How consistent you are with exercise is much more powerful than when you do it. To maximize each session, choose a type of cardio exercise that uses up the most energy—cardio workouts such as walking, running, cycling, dancing, and using machines like the elliptical trainer burn the most calories per minute. Then, work at the highest intensities you can handle. Keep in mind if you're new to exercise, you need to take it more slowly than someone who's fit and can push him or herself.

The recommendation from the American College of Sports Medicine is to do cardio on most days of the week—that means five days or more. If you're fit, you may fall into the trap of thinking that if you can't work out for a full hour, then you'll have to skip that day's exercise session. The danger of this all-or-nothing mentality is that one or two skipped days can turn into weeks, or even months, of missed workouts.

Burn, baby burn—it adds up!

It's better to squeeze in little bits of exercise and make the most of them. Even exercising for a mere 10 or 15 minutes on "non-workout" days (at a high intensity, if you're fit enough to do so), can have a dramatic effect on your fitness level and on weight management over the course of a few months. Do the math: In a month, three days a week of 15-minute workout blasts can add up to three entire hours of exercise that you otherwise might have skipped.

These super-short workouts can be done at home at any time of the day. If you have a cardio machine like a bike or treadmill, jump on. If you have a fitness DVD, push 'play' and start a workout segment. If you have an iPod, dance vigorously to a few songs, or take a brisk walk, or jog around the block.

No matter when you do it, exercise increases your daily energy expenditure, or how many calories your body burns all day. To lose weight and decrease body fat, you need to expend more calories than you eat. So any exercise at any time of the day will contribute to weight loss as long as you're burning more calories than you are eating overall.

An optimal fat-burning time of day?

It's debatable whether you get an extra edge at one time or another. As you've already found out, there are seemingly plausible explanations for why doing cardio at various times of the day might affect your calorie burn differently. But there's no conclusive evidence that there's an optimal time to exercise. Even if you can eke out a few more calories at one time or another, what's more powerful in accumulating the biggest calorie burn is to exercise as often as you can. And when you do, exercise as vigorously as you can. (Or, if you are not fit enough to push yourself, work at easier levels and burn more calories during the session by adding additional minutes to your session.)

Generally, with any cardio exercise, the harder you work, the more you burn. How energetic or tired you are can affect how hard you push yourself. How you feel may be a key factor when choosing your optimal workout time. If you stumble out of bed half-awake in the morning and are too sleepy to put much into your power walk, you'll probably not get as much out of the same workout compared to if you exercised later in the day, when you're energized and ready to rev things up. On the other hand, if you're fatigued from a stressful day, you may not be able to push as hard in the evening as you would if you got the session out of the way earlier.

Many people are chronically sleep deprived. Therefore, perhaps more important than worrying about when you work out is being careful to get enough sleep. You'll get the most benefit from your workouts if you feel rested enough every day to push yourself to work as hard as you comfortably can, no matter what time they are at, or how long they last.

Keep in mind that not only does sleep play a role, but some people are morning people and some people are night people. So how alert and energized you are during morning or evening workouts may depend on your natural biological rhythm.

How well-fueled you are also affects the calories you burn and store. Remember that if you do a tough, long workout first thing in the morning without having eaten for hours, or in the evening after not having had anything to eat since lunchtime, you may be less capable at working at higher, greater-calorie burning intensities.