THE BEST TIME TO EXERCISE DEPENDS on your gender and goals (burning fat or getting stronger). Today we look at morning versus evening exercise.
While there is no “wrong” time to get in some physical activity, a new study suggests that you may be better off exercising later in the day or doing short bursts of activity (rather than an early morning exercise).
Exercise timing is increasingly a part of the exciting field of chronobiology, a discipline that focuses on how our internal clocks influence virtually every aspect of our physiology.
“A bear, however hard he tries, grows tubby without exercise.”
― A.A. Milne, Winnie-the-Pooh
Circadian Rhythms and Clock
Circadian rhythms are internally driven cycles that rise and fall throughout the 24-hour day. These rhythms help us to fall asleep at night and wake up in the morning.
We have a master circadian clock in the brain, with this timekeeper synchronizing and controlling our cycles. The sun’s light and the dark cycle resets our circadian clocks. Here are some of the regulated cycles:
- Sleep/wake cycles
- Hormonal activity
- Body temperature rhythm
- Eating and digesting
How do circadian rhythms work?
First, our brain’s cells respond to light and dark. After our eyes capture environmental changes, nerves send signals to different cells about when to be awake or asleep. These initial cells then signal other cells in the brain, activating other functions to make us tired or keep us alert.
Those cells then send more signals to other brain parts, activating other functions that make you more tired or alert. Hormones such as melatonin and cortisol play important roles in the process.
Melatonin is a hormone that promotes sleep — we release more melatonin at night and less during the day. Cortisol increases alertness, and our body creates more of it in the morning.
Other hormones setting the circadian rhythm include vasopressin, acetylcholine, insulin, and leptin.
Other factors
Other factors involved in our circadian rhythms include temperature and metabolism. Our temperature drops with sleep and rises during our waking hours. Metabolism rates change throughout the day.
Work hours, stress and anxiety levels, physical activity, and other lifestyle factors can influence your circadian rhythms.
Exercise, time of day, and insulin resistance
Two new studies suggest that, given a choice, we may be better off exercising later in the day or engaging in brief bursts of activity.
In the first study, researchers examined how we may manage insulin resistance (a condition that can lead to type 2 diabetes) with physical activity. Here are the results:
Exercising in the morning did not reduce insulin resistance in the study’s participants, but afternoon or evening exercise improved insulin resistance.
More specifically, moderate-to-vigorous physical activity in the afternoon dropped insulin resistance measures by 18 percent, with evening exercise associated with a 25 percent reduction. These percentages are relative to physical activity spread throughout the day.
Here are some other differences that emerged when comparing the groups:
- For females, fat burned away better in the morning. The early female exercisers dropped an average of three percent more body fat than the evening exercisers (with most of the loss from waistlines). The morning exercisers lost about seven percent more belly fat than women working out in the evening. (None of the subjects’ body weight dropped, given they added muscle as they lost fat.)
- Morning exercise also lowered blood pressure in females more than in evening exercisers.
- Evening exercise by women amplified strength gains, with the evening group improving upper body strength by seven percent more than the morning group.
- Evening exercise by men led to lower cholesterol levels; the morning group surprisingly raised their own. Fat burning increased in the evening exercise group, too.
- Any time for exercise increases men’s strength and fitness.
Women hoping to drop inches around their middle may wish to consider morning workouts. For those trying for strength improvements, evening workouts may be better.
For men, the time for exercise did not influence strength and fitness, but evening exercise may have some health advantages.
Study details
The study included 56 participants, with more than half self-identifying as women. After testing the volunteers’ strengths, fitness, and health, the researchers randomly divided them into two groups. The first group exercised four times weekly in the morning, between 6 and 8 a.m. The second group exercised in the evening, between 6:30 and 8:30 p.m.
The groups performed identical workouts. Once weekly, they lifted weights. The following day, each participant did 35 minutes of interval training (cycling, running, or swimming as hard as possible for a minute, resting, and repeating). On another day, all participants did yoga or Pilates. Each ended the week with an hour of cycling, running, or another aerobic exercise.
Both groups did this program for 12 weeks, then returned to the lab for re-testing. All participants appeared faster, fitter, leaner, healthier, and more flexible, irrespective of the workout time.
Insulin resistance is a condition in which the cells in your fat, muscles, and liver do not respond well to insulin and cannot use blood glucose for energy. As a result, the pancreas creates more insulin. Your blood sugar levels rise over time.
Insulin resistance syndrome includes multiple problems, including type 2 diabetes, obesity, high cholesterol, and high blood pressure (hypertension). As many as one in three Americans suffer from insulin resistance syndrome, also known as metabolic syndrome.
Insulin resistance (metabolic syndrome) signs include:
- A male waistline over 40 inches and a female one more than 35 inches
- Blood pressure of 130/80 or more
- A fasting glucose level of more than 100 mg/dL
- A fasting triglyceride level more than 150 mg/dL
- HDL cholesterol below 40 mg/dL in males and 50 mg/dL in females
- Skin tags
- Patches of dark, velvety skin (acanthosis nigricans)
Exercise snacks or short bursts
A separate study reports that short exercise bursts (physical activity snacks), done throughout the day, break up periods of prolonged sitting. In addition, the approach can build muscle by using more amino acids from food.
I weave physical activity into my day, including walking and an occasional body squat during the day.
My take on exercise— Any time is the right time
First, exercise timing is a subject worthy of more study. The current study shows that morning exercise may not reduce insulin resistance, but afternoon or evening exercise improves insulin resistance. Timing may fine-tune particular exercise-related improvements.
We need confirmation, but the findings are provocative. We know that any exercise at any time can improve health.
Second, interrupting prolonged sitting with short periods of activity (physical activity snacks) can improve our dietary amino acid use to build muscle. For me, minimizing sedentary time is essential to achieving good health. I regularly take the stairs and walk to chat with a colleague (rather than calling or texting) as much as reasonably possible.
The information I provided in this blog is for educational purposes only and does not substitute for professional medical advice. Please consult a medical professional or healthcare provider if you seek medical advice, diagnoses, or treatment. I am not liable for risks or issues associated with using or acting upon the information in this blog.
Thank you for joining me today for this look at morning versus evening exercise.
