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Your morning walk, no matter how far, can help you live longer

Science says it's okay if you only get 15 minutes of exercise per day (but the more the better)

Luke Whitcomb

Physiology and Biomedical Sciences

Colorado State University

The number of individuals living with a chronic disease has reached an unprecedented level in the US. Sixty percent of Americans have at least one chronic disease, while 40 percent have two or more.

Research has long shown that physical activity can powerfully improve health and reduce chronic disease risk. Consistent physical activity has been shown to reduce blood pressure by around five percent and improve insulin sensitivity. But, only 53.3 percent of US adults actually meet physical activity recommendations of 150 minutes of moderate-intensity activity per week. 

Encouragingly, research published in 2020 has shown that physical activity does not even need to be undertaken in organized bouts to be effective. For this study, researchers had 4,840 US participants above the age of 40 wear pedometers for up to seven days days between 2003-2006 to determine the average number of steps each person took per day. Researchers also collected participants' health information and used the US National Death Index to track whether participants died between the time they participated in the study and December 2015.

Greater number of steps per day was significantly associated with lower mortality rates: compared with individuals who took 4,000 steps per day, taking 8,000 steps per day was associated with a 51 percent reduction in risk of death. Those who took 12,000 steps per day had 65 percent less risk. Importantly, these steps were the totals accumulated throughout the day, not necessarily all at once. The intensity of the participants' walking did not have a strong effect on the health impact.

This study highlights that the total volume of physical activity you undertake, spaced throughout the day, is associated with improved general health. You don't need to be a powerlifter or run for an hour three days a week at a gym to be healthy. Simply incorporating a brisk morning walk daily while listening to a podcast, hiking with family on the weekends, or pulling up an at-home yoga video a couple times a week can have a tremendous impact on your health. 

This study corroborates findings from a study in Taiwan published in 2011, which asked 416,175 individuals aged 20 years and older between 1996-2008 to fill out health questionnaires regarding their weekly leisure time physical activity (LTPA). These self-evaluations were composed of only three questions aimed at gauging the type, intensity, and duration of weekly physical activity performed in the participants' "spare time." The average participant followed up with researchers for eight years after the initial questionnaire, to provide subsequent reports of their physical activity. 

Using this data, participants were sorted into five categories based on their estimated weekly amount of LTPA, calculated as the product of the total duration of their movement (in hours) and their daily exercise intensity, measured in METS (a "MET" is the unit of energy it takes to sit quietly).

person's wrist with an apple watch

 Photo by Kamil S on Unsplash

Researchers found that even those in the "low volume" group, who completed well below the recommended 150 minutes of weekly exercise, had a 14 percent reduction in all-cause mortality. This effect was particularly pronounced among diabetic individuals: those in the low-volume group had 22 percent less risk of death than participants in the inactive group. Importantly, the overall results of this study results also showed that every additional 15 minutes of daily exercise beyond the minimum 15 minutes reduced all-cause mortality in the group by 4 percent.

Both of these population studies, however, have big limitations. They are excellent examples of observational studies: participants live their lives without researchers controlling any variables which could interfere with scientific results. For example, perhaps individuals who were more physically active might also tend to have healthier diets, contributing to risk of death and disease. For scientists to eliminate this "confounding" variable, every participant would need to eat exactly the same type and amount of food each day. Other potential confounding variables include family history of disease, risk injury associated with vocation, exposure to toxins, and many others. Taken together, observational studies can only infer correlation between a variable (in these studies, amount of physical activity) and an outcome (death). However, because such a huge population was studied, there is a greater likelihood that the impact of these confounders was minimized.

Populations from different ethnic, national, or racial backgrounds can also be different from one another. This latter study was conducted in Taiwanese men and women above the age of 20 of relatively high socioeconomic status. The researchers who conducted it noted that, on average, East Asian people tend to be less physically active than individuals in western countries and also tend to exercise at lower intensity. Some research has also shown that Asian individuals may have twice the risk of developing diabetes and higher risks of hypertension and cardiovascular disease than people of European origin with the same weight and height. 

Despite these complications, cardiovascular disease is a leading cause of death in both the US and China, and both countries have seen dramatic declines in levels of physical activity over the past decades. In addition, it has long been documented that the Chinese diet has changed over time to resemble the "western" diet: one typically high in fats, sodium and protein. Traditional East Asian foods include less greasy, relatively low-calorie items such as pickled vegetables, salted fish, tofu, and rice. So, it reasonable to generalize the findings of the Taiwanese study to the recent US-based research. 

If you are having trouble getting recommended 150 minutes of medium- intensity exercise per week, do not be discouraged. Start where you are, and focus on moving more. Setting small goals of 15 minutes each day – including going on several short walks a day – is still effective for improving your health. Starting small may help make exercise easier to incorporate into a busy schedule and could help build the habits and confidence required to gradually increase your daily dose. Find what works for you: walking, jogging, swimming, hiking, dancing, a push-up competition with your friend. They all count as physical activity – and science says they can all help you live a longer, healthier life.

Comment Peer Commentary

We ask other scientists from our Consortium to respond to articles with commentary from their expert perspective.

Jayati Sharma

Genetics and Epidemiology

Johns Hopkins University

Understanding disease risk reductions outlined per amount of physical activity is important to everyone looking to improve their health. Further, the nuanced explanations of these risk reductions in the context of confounders and population-level differences is important to understanding the individual-level benefits we can gain from exercise. Diet, physical activity, sleep, and genetics are all important factors  that will be the continuing subjects of future interventional studies to understand how to improve human health. 

Anisha Kalidindi

Molecular Biology

Ohio State University

I think this article did a particular wonderful job of including the context in which these studies were done and what implications this might have of our interpretation of the data was done well. Often it is easy to assign causality to these type of large observational studies but I liked how this was clearly explained to be correlation. It can get overwhelming to implement life style changes when the literature has so much evidence on what best practices are whether it intensity or type. So it is encouraging to see that even a small life style intervention can have significant impact.