In 2007, researchers led by Dr. Alia Crum at Stanford University in California recruited 87 hotel workers whom they knew received a sufficient amount of weekly exercise simply by performing their jobs. They weighed and measured them, calculated body fat percentage, body mass index, waist-to-hip ratio, measured their blood pressure, and randomly split the 87 into two groups.

Isolated from one another, each group then received about 20 minutes' worth of slightly different information.One group was told about all the health benefits of exercise and that simply by performing their jobs they reached the suggested weekly amount of it needed to reap them. The other group was also informed about all the health benefits of exercise, as well as all the possible ways to get the recommended weekly amount of exercise.They were never told, however, that they got enough exercise simply by doing their jobs - even though that was clearly the case.The researchers did nothing else with the two groups until they again weighed and measured them and took their blood pressure four weeks later. The group that was told their jobs provided enough exercise to help their health recorded an overall decrease in body weight, body fat percentage, body mass index, waist-to-hip ratio, and blood pressure.Why?They were never given an after-work exercise regiment to follow. They were never instructed to follow a particular diet or cut calories.What could have possibly created such across-the-board health improvements in only a month? How about the inestimable power of the mind?In search of some sort of estimate, Dr. Alia Crum, the leader of the 2007 Stanford research, teamed with Octavia Zahrt, a doctoral candidate at Stanford's Graduate School of Business, and did some serious number-crunching. They reviewed three prior national surveys about health and fitness done between 1990 and 2006 that contained the responses of 61,141 U.S. adults and a follow-up mortality study from 2011.But they approached the topic in a different manner than the 2007 research. They wanted to know if feeling as if you weren't doing enough exercise - regardless of whether you were or weren't - could adversely affect your health.They took this approach, interestingly enough, because of Zahrt. Before she came from across the Atlantic to study at Stanford, she thought using a bicycle for transportation and some occasional workouts in the gym were enough to keep her fit.When she saw how seriously and strenuously many Californians worked out, though, she couldn't shake the sense that she just wasn't doing enough and wondered if that negative thought - just that thought alone - could eventually hurt her health.She wrote about this in a paper for Crum's class. It became the catalyst for their research.And the numbers they crunched revealed that Zahrt's ruminations were right on: if you believed you were not working out enough - even if the numbers indicated you really were - it tended to hurt your health. In fact, even after Crum and Zahrt used statistical models to account for age, body mass index, chronic illnesses and other factors, they found that individuals who believed that they were less active than others their age - again, whether the belief was accurate or not! - were more likely to die in the follow-up period than individuals who rightly or wrongly believed the opposite.Up to 71 percent more likely.To summarize their findings, Zahrt offered this quotation to Tim Newman for the article he wrote for Medical News Today: "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."Her quotation should serve as more than a summary of the study. It should get you to thinking about the prodigious power of the mind, and if you are using that power positively or negatively.Because if "thinking you are not exercising enough can also harm your health," wouldn't the same hold true if you're thinking you're not eating properly or not sleeping enough - even if you were?Could being critical of yourself, a mindset we often see as being needed to take your health and fitness to a higher level, actually do the opposite?And how are you supposed to think about aging? If Crum and Zahrt's findings are indeed true, wouldn't any honest thoughts about getting older also be unhealthy ones?At this point, you need to know that the design of this week's column is to ask unsettling questions rather than answer them. And for good reason.For years, the statement, "It's all in your head," has been used to dispel false notions. In fact, the phrase is often used to describe illnesses with no physical basis at all, or ones that are even faked.But if subsequent studies support the work already done at Stanford, a few years from now the saying won't be just for false notions.But for how all notions either help or harm your health.