Want to live longer? Exercise in the afternoon, finds research

study with more than 90.000 evaluated individuals shows that the best time to exercise is in the afternoon, with an advantage over those who exercised in the morning or at night. However, if you prefer to exercise in the morning or evening, don't be discouraged. The study also found that physical activity performed in anytime of the day is better for longevity than no exercise.

Additional research indicates that there are unique benefits to exercising in the early hours of the morning, suggesting that the best time to exercise depends on the training goal.

Why care about exercise time? 

There is growing evidence that the health effects of exercise depend to some extent on when we are active.

Previous studies have shown that people at risk of diabetes improved blood sugar control when exercising at night, rather than in the morning, while other research has indicated that people lost more body fat when they exercised early instead of later in the day.

However, most of these studies were limited and inconsistent in their results, making it difficult to draw conclusions about the best time to exercise.

A new study helps overcome these limitations.

Published this month in the magazine Nature Communications., the study pooled data from 92.139 men and women who participated in the UK Biobank — a UK adult health study — and used a activity tracker for a week.

Using data from the trackers, the researchers categorized volunteers according to how often and when they moved, looked at mortality records for up to seven years after people joined the Biobank, and compared movement patterns and deaths.

Results showed that men and women who frequently engaged in moderate or vigorous physical activity (equivalent to brisk walking) lived longer than people who rarely exercised, no matter what time of day they moved.

However, experts point out that the time of day you exercise can have subtle but important effects on your health. 

The researchers found that people who exercised between 11 a.m. and 17 p.m. — or spread their physical activity throughout the day — had less likely to die early from heart disease or other causes (except cancer) than those who mostly exercised before 11 am or after 17 pm.

The afternoon seems to be especially beneficial for heart health, as this is statistically the time of day when people are least likely to have a heart attack. Although the benefits of exercising in the afternoon are more pronounced for men and the elderly, the study results suggest that the timing of exercise may be important for maximizing daily health benefits.

However, many people may find it logistically challenging or undesirable to exercise in the afternoon, in the middle of the work day. For these individuals, it is important to remember that physical activity at any time of the day it's better for your health than not exercising at all.

For those who have difficulty exercising in the middle of the day, a recent study of healthy mice using small treadmills offers a promising solution. 

rats on treadmills

This study built on separate research from last year, where researchers from several institutions cataloged nearly every molecule that changed in the body tissues of mice, depending on when they ran. 

The researchers were surprised to find that the changes were especially pronounced in the animals' fatty tissues. They expected that the animals' muscles and liver, which help provide fuel for exercise, would be most affected.

For the new study, the researchers decided to focus on fat and how timing of exercise affects the body. They made male rats run on small treadmills for a while or stand still without using the treadmill.

Some rats ran a few hours after waking up — equivalent to half the morning for us — while others ran a few hours during the period when animals normally wind down and rest. Some of the animals didn't eat before exercise, while others got a little bit of kibble before training.

The scientists repeatedly drew blood and fat tissue from the animals after exercise. They found that animals that ran within a few hours of waking up showed a significant amount of activity in adipose tissue. 

The fat cells of these animals released many more fatty acids, which are the building blocks of fat, into the bloodstream, ready to be used as muscle fuel. Furthermore, the remaining adipose tissue showed a bigger increase on biochemical markers of heat production and mitochondrial activity than fat from animals that ran at night. Some genes related to fat metabolism also showed more activity.

How to decide the best time to exercise?

Juleen Zierath, teacher at Karolinska Institute, claimed that a single morning exercise session could lead to greater fat burning and weight loss over time. However, choosing the best time to exercise remains a complex issue. For example, exercise performed in the afternoon may be preferable for longevity, while morning activities are better for reducing waist circumference.

According to Jeffrey Horowitz, a professor at University of Michigan who studies exercise and metabolism, the new study identified fascinating effects, but also complicates the question of the best time to exercise. According to Zierath, the time you exercise will not make any big difference.

The results of the study suggest that the frequency of physical activity is more important than the time at which it is performed in relation to the benefits for longevity. 

Zierath notes that while there is a difference in the effects of morning and evening exercise on fat burning, it would likely be small. She also adds that, over time, these small changes can become significant. Therefore, if the goal is burn more fat, it can be advantageous to exercise before noon, but if the goal is longevity, it is better to move more during the afternoon. Regardless of the time, it's important to just get up and move.

See more:

10 apps to exercise without leaving home

10 health and exercise apps to complement your routine

Source: Washington Post, Nature, Physioc, Science Directly, (PNAS)