During their visits to the clinic, these men and women had completed the typical series of health and fitness measurements and also filled out an exercise questionnaire in which, among other things, they asked about strength training. They were asked if they did “muscle strengthening exercises” and if so, how often and for how many minutes per week.
The researchers then began collecting the data and comparing people’s weights and other measurements between each clinic visit. Using the BMI as a unit of measurement, about seven percent of men and women had become obese in the six years after their first visit to the clinic.
However, BMI is a poor approximation of body constitution and is not always an accurate measure of obesity. Therefore, the researchers also looked at changes in waist thickness and body fat percentage to see if they had become obese. Based on the criteria waist diameter greater than 100 centimeters in men and 90 in women or body fat percentage greater than 25 percent in men and 30 percent in women, up to 19 percent of the participants developed obesity over the years.
However, the researchers found that lifting weights changed these results and significantly reduced the risk of someone being overweight, regardless of which measurement parameters were used. Men and women who reported strengthening their muscles several times a week for a total of one to two hours per week were 20 percent less likely to become obese over the years, based on BMI, and 30 Percent less, depending on the thickness of the waist or the body fat percentage.
The benefits didn’t change when the researchers checked the variables of age, gender, smoking, general health, and aerobic exercise. People who did aerobic exercise and lifted weights were much less likely to become obese. However, the same was true of those who only lifted weights and reported doing little or no aerobic exercise.
The results suggest that “lifting weights has many benefits, even if you don’t do it often,” says Angelique Brellenthin, professor of kinesiology at Iowa State University who led the new study.
Of course, the research has been observational and does not show that resistance training prevents weight gain, just that the two factors are related. Nor was it considered people’s diet, genetics, or health habits, which could affect the risk of obesity.