Breaking research finds that simply believing that you do not exercise enough might shorten your life, regardless of your actual activity levels. Are the psychologic and physiologic aspects of fitness more entwined than we thought?

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How fit do you think you are? The answer may be important for your health.

Exercising and staying fit is, of course, important for living a long and healthy life. However, almost 1 in 10 premature deaths worldwide are attributed to physical inactivity.

In the United States, around 80 percent of adults do not meet the recommended levels of exercise, despite the efforts of media, school, and workplace programs.

Although the struggle to get people moving is ongoing, over recent years, another important factor has come to the fore: our perception of our own activity levels.

Our perceived activity levels may not reflect our actual activity levels. In fact, study author Octavia Zahrt, Ph.D., says, “If you live in an area where most of your peers are really fit, you might perceive yourself as relatively inactive, even though your exercise may be sufficient.”

“Or, if you believe that only running or working out at the gym count as real exercise, you may overlook the exercise you are getting at work or at home cleaning and carrying kids around.”

A study conducted in 2007 by Dr. Alia Crum (also involved in the present research), of Stanford University in California, illustrates this surprising psychological interaction.

That study concentrated on 87 hotel room attendants working across seven hotels. Each of the participants routinely met exercise guidelines, purely through the work that they carried out each day at their respective hotel.

The researchers conducted a 20-minute intervention: in a nutshell, they informed an experimental group of workers that they were all were meeting their daily exercise needs through their physical jobs, explaining the benefits of such an active lifestyle. A control group of hotel workers were given information about recommended exercise levels but were not informed that they routinely met the required physical activity levels.

After 4 weeks, when the two groups were compared, the experimental group showed a decrease in blood pressure, weight, body fat, body mass index (BMI), and waist-to-hip ratio.

These results seem nothing short of incredible: a psychological intervention with the ability to change physiology for the better.

Drs. Zahrt and Crum recently set out to investigate this relationship in a larger sample, and their results are published this week in the journal Health Psychology.

They took data from three nationally representative samples of U.S. adults, with a total sample size of 61,141. These individuals were surveyed from 1990 to 2006, and mortality data were collected in 2011. The researchers had access to detailed medical records and information about disabilities, mental health, BMI, gender, age, education levels, and race.

Participants were given questionnaires that included a range of questions about fitness and activity levels. Information was collated about the types of activities they had recently taken part in, as well as their duration and intensity. For one phase of the data collection, participants wore an accelerometer that measured their actual levels of activity.

Importantly, the questionnaires gauged how physically active the individuals thought they were with the question, “Would you say that you are physically more active, less active, or about as active as other persons your age?” They also rated themselves on a general health scale from 1 (excellent) to 5 (poor).

As suspected, the participants’ perception of their own activity levels did not correspond to their actual activity levels, and the effect of this was nothing short of startling.

Individuals who thought they were less active than their peers were 71 percent more likely to die during the study follow-up period than those who believed that they were more active. This effect remained significant even after controlling for factors including their actual levels of exercise, chronic illness, and age.

Most people know that not exercising enough is bad for your health. But, most people do not know that thinking you are not exercising enough can also harm your health.”

Octavia Zahrt, Ph.D.

The results are intriguing and beg the question of how this is possible. The current study cannot answer this question, but the authors put forward some theories.

One such theory is the placebo effect. Researchers know only too well that a tablet with no active ingredients can make a patient feel better (or worse, in a phenomenon known as the “nocebo effect”). The placebo effect is well studied and incredibly robust. Although the mechanisms behind it are still poorly understood, it could be playing a role here.

Another theory is that the feeling of doing worse than your peers and worrying about the negative health consequences might make an individual feel fearful, depressed, and stressed, which, in turn, could negatively impact health.

A third potential explanation is outlined by the authors of the study. They say, “A room attendant’s awareness that she is getting exercise at work might increase her self-efficacy and commitment to a healthy lifestyle, and motivate her to act on this “active” identity by making beds more energetically or exercising in her leisure time.”

Although more research is needed, the take home message is this: the key to living a long, healthy life is staying active, as well as believing that you are being active.