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Exercise: Is 15 Minutes a Day Enough?

Written by: Tom Nikkola – Director of Nutrition & Weight Management

Key take-aways:

  • Don’t rely on news headlines to direct your nutrition and exercise choices.
  • While a little exercise is good, more is better, at least to a point.
  • High-intensity exercise can provide better health benefits, but duration should be monitored, and should be used only with individuals who are properly conditioned.
  • Exercise plays a critical role in long-term weight management, and committing to only 15 minutes per day is not likely enough to support weight loss or management.
  • Fifteen minutes is a good place to start, but at least 30 minutes a day (ideally 45-60 minutes), five times a week produces the greatest results.

How little can you exercise and still be healthy? Five minutes a day? Ten? According to many news headlines, playing off a recent study on the topic, it sounds like 15 minutes a day might be enough. Taking just pieces out of a recent study on exercise and health, headlines such as Exercising 15 minutes a day adds 3 years to life expectancy, Are you ready for your 15 minutes of exercise? and Exercise 15 minutes a day for a longer life recently made the news. As so often happens, the headlines start creating confusion and mislead people about what’s required for optimal health.

The news stories came from a recent study published in the journal, The Lancet.[i] The study looked at a large population of people living in Taiwan. It compared their risk of death and a few diseases for individuals who were sedentary and those who exercised for various lengths of time each week. Not surprisingly, those who did not exercise at all were more likely to die earlier or end up with diseases such as cancer, diabetes or cardiovascular disease.

Also not surprisingly, those who stated they exercised an average of 90 minutes a week, or 15 minutes per day, had a reduced risk of dying or developing those diseases compared to those who were sedentary. Unfortunately, that’s the main point the media ran with regarding the study. As usual, there’s more to the story, and in this case, more to the study.

Just 15 minutes?

More than 416,000 people completed questionnaires and were followed for an average of just over eight years. Compared to those who exercised at the lowest level (15 minutes per day), those who were sedentary had a 17% increased risk of dying. The way this was translated? Those who exercised 15 minutes per day would live three years longer than those who were sedentary. Sedentary individuals appeared to have an 11% increased risk of developing cancer compared to those who exercised 15 minutes a day, as well. While 15 minutes a day showed some benefit, those who exercised at least 90 minutes a day more benefited more. So, although 15 minutes per day provides some benefits, the news stories made it sound like exercising 15 minutes a day was a bigger deal than it really was.

Aside from overemphasizing the benefits of just 15 minutes per day of exercise, the researchers and newswriters made another unfounded assumption: People will be more willing to exercise 15 minutes a day than they would 30 minutes a day. The researchers wrote, “The minimum amount of exercise reported in this study is half of that recommended worldwide, but individuals are more likely to do 15 minutes of daily exercise than they are 30 minutes of daily exercise.” It seems plausible that people would be more willing to exercise if they only had to do 15 minutes a day, but this has never been proven.

As I told Fox News recently see (interview below), telling people they only need to do 15 minutes of exercise a day makes it easier to justify skipping a workout on any given day, with the thinking that it can easily be made up the next day. It’s the same thinking that gets us in trouble with food (I’ll just start my diet on Monday. Just one cookie won’t hurt me. I’ve already eaten poorly today, so I might as well eat whatever I want the rest of the day). As humans, we’re really good at justification. There’s a great possibility that changing the standard from 30 minutes a day of exercise to 15 minutes a day will only make our sedentary lifestyles more sedentary, not more active.

Exercise does more than prevent death and disease.

Exercise plays a role in our ability to manage weight. Although most people have little success with losing weight by focusing only on exercise and overlooking nutrition, exercise does play a significant role. The benefits of exercise don’t necessarily come from how many calories are burned, although it’s a small part of how exercise supports weight management. More important is how exercise affects the body’s hormones, which regulate metabolism, support changes in lean body mass, affect blood sugar levels, and eventually make the body more efficient at burning extra body fat. A 15-minute workout each day is not likely enough for the average overweight individual to gain much benefit in terms of weight management.

Exercise duration: More is better, to a point.

Exercising 15 minutes per day is a good start, especially if someone is getting no exercise, but exercising more provides more benefit. According to the study, health benefits increased as exercise duration increased, up to a point of 90 minutes per day — where the benefits plateau. Once people began exercising more than an hour and a half each day, the health benefits were not any greater than those who stopped at 90 minutes. However, the health benefits from 60-90 minutes per day were far greater than 15 minutes per day. While it’s possible to get a healthy dose of exercise in a 15- to 20-minute workout, it requires an individual to produce a significant amount of intensity. If your workouts are usually at a moderate level of intensity, they should be at least 30 to 60 minutes in duration.

Although 15 minutes is better than nothing, so is five minutes, but that doesn’t mean we should be aiming for five minutes just because it’s better than nothing. Committing to at least 30 minutes will give you enough time for a reasonable warm-up and time to produce enough intensity for a positive effect on your metabolism.

Shorter duration, greater intensity.

As the study’s authors pointed out, “Vigorous-intensity exercise yielded similar or greater health benefits in terms of all-cause mortality reduction than did moderate-intensity exercise at the same volume of activity or at the next higher volume of activity.” That means individuals who train with a high level of intensity gain a similar benefit to those who exercise at a more moderate intensity level but for a longer period of time.

An individual may gain a similar benefit from a workout that includes alternating sprinting and walking (interval training) for 20 minutes as compared with a workout consisting of 60 minutes of walking. In fact, a sprint workout may be even better from a fitness standpoint, because sprints have a better effect on the body’s hormones and muscular development.

A couple of cautions regarding exercise intensity, whether the exercise is cardiovascular or strength training: First, intensity should only be increased once your body is ready for it. If you’ve been sitting for the past few years, sprinting is a really bad idea and can result in a serious injury. Second, high-intensity exercise should be done for an abbreviated length of time, especially for those who have a high level of stress in their life. High-intensity exercise that lasts longer than about 45 minutes leads to a large increase in the stress hormone cortisol. Not a good situation.

How long is enough?

Our lifestyles are more hectic than ever, which often forces exercise to be just another thing on the to-do list. It may be tempting to ask, “What’s the least I can do to still get some benefit?” Yes, some is better than none, but before you look for the right answer, think about this. There are 168 hours in a week. You should be sleeping 8 hours per night, which leaves 112 hours per week you’re awake. According to the study mentioned above, an hour and a half per week of exercise will give you some benefit. That’s 1.3% of your “awake-time.” Committing to an hour a day, six of seven days per week would provide significantly more benefit, and six hours is only 5.3% of your “awake-time” or 3.6% of your total weekly hours available.

Your body was made to move. Your body was designed to be lean, healthy and strong. Unlike most any other machine you own, the more you use your body, the better it runs. If you’re just starting out, 15 minutes can be a place to start, but work up to 30 minutes as soon as you can. Eventually you’ll find 45-60 minutes, five time a week is probably just right.

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

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[i] Wen CP, et al. Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. The Lancet. 2011 Aug 16 doi:10.1016/SO140-6736(11)60749-6

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