A fascinating study conducted at Stanford University and reported in the Nature Human Behavior journal indicates that beliefs about us are more powerful in shaping our behavior and our physiology than our DNA.
The 200 men and women in the study first provided saliva samples for genotyping. Then they were divided into two groups: the exercise group and the food group. The exercisers were put on a treadmill and instructed to run as long as possible. While running, their oxygen uptake and lung capacity were measured.
The others were given a 480-calorie liquid meal and told to finish all of it, and then describe how full they felt. While this was proceeding, blood was drawn to test for certain hormones known to make people feel full.
At a later time, all the subjects returned. The treadmill group were individually told their genetic testing showed they would have low endurance and would find prolonged exercise difficult. This was not true. After receiving the negative, bogus information, they were given another stint on the treadmill. Surprisingly, they tired more quickly than the first time. Even more shocking, their oxygen uptake and lung capacity were also diminished. Thus, the false information not only changed their behavior, but also changed their body physiology.
The other group were also given untrue information. Some were told they lacked the gene that tends to make us feel full and, thus, they were in danger of becoming over weight. Others were told they had the satiety gene and would feel full quickly. When the high calorie drink was consumed again, those told they lacked the gene reported little feeling of fullness. Those told they had the gene reported feeling full quickly. Once again, the physiology, namely the hormone levels, went along with the beliefs and behavior.
At the conclusion of the study, participants were given the true information about their gene profile. As an additional study, the researchers looked at how much exercise capacity and eating behavior were influenced by the actual genetic profile of each person. The finding showed that the genes were considerably less influential then the belief system, even though these beliefs were based on false information.
What this boils down to is the fact that what we believe about ourselves can actually change our behavior and physiology, at least when it comes to exercise capacity and feelings of fullness after eating. Other aspects of health and behavior may not react the same way. But, at least in these two areas and possibly in many more areas of your life, YOU ARE WHAT YOU BELIEVE.