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Sitting in front of a work computer during the daily 9-5. Sitting to chat with a friend. Sitting to eat dinner. According to a new University of Florida study, the amount of time some people spend sitting could affect whether they develop Type 2 diabetes later in life.
Women who sat more than 16 hours during their waking day had the highest risk of developing diabetes. The researchers also found that the high risk of diabetes remained even if they otherwise exercised five days a week, 30 minutes per day.
“This would give you some evidence that your sitting is a risk factor for what’s going to happen in the future, similar to the way your cholesterol today will predict if you will get a heart attack tomorrow,” said Todd Manini, Ph.D., who led the study. Manini is an assistant professor in the UF College of Medicine Department of Aging and Geriatric Research and a member of the UF Institute on Aging.
Manini and colleagues also found that obese women were much more likely to develop diabetes than overweight and normal-weight women who sat for the same amount of time.
The researchers analyzed data collected from the national Women’s Health Initiative study. Launched in 1991, the National Institutes of Health study was a 15-year research program that involved 161,808 women. It gathered data on the most common causes of death, disability and poor quality of life in postmenopausal women.
The UF researchers examined surveys from 88,829 women aged 50-79, none of whom initially were taking medications for diabetes. The researchers tracked their sitting time and weight in each annual survey, and noted which women developed diabetes. In general, nearly 11 percent of women ages 20 and older have diabetes, according to the American Diabetes Association, and nearly 27 percent of people over 65 will develop diabetes, according to the National Diabetes Education Program.
The study participants’ responses were broken into eight categories, with two extremes: women who sat fewer than seven hours per day and women who sat more than 16 hours per day.
“With computers, our jobs have gotten progressively more sedentary. One percent of women in the original study reported sitting more than 16 hours per day. We might expect those numbers to be higher today,” Manini said.
The longer the women sat, the higher their risk for developing diabetes. Their risk began increasing sharply when they sat between 12 and 15 hours per day. These women had about a 10 percent chance of developing diabetes compared to about 8 percent or less for women who sat for shorter periods of time. If the women sat more than 16 hours per day, the risk rose to about 13 percent.
But the risks really shot up if the woman was considered obese. Compared with normal-weight and overweight women, whose risk of diabetes increased only slightly if they sat for more than 16 hours, the risk of diabetes for obese women who did not exercise jumped from about 19 percent to 23 percent when they sat that long on a daily basis. Even if obese women reported exercising 150 minutes per week, their incidence of developing diabetes was still 13 percent, about 5 percent higher than women who exercised but sat fewer than 15 hours.
“The study suggests sitting is an independent contributor to a person’s risk of developing diabetes because the study controlled for a host of variables that would predict diabetes onset: demographics, smoking, diet and family history,” said Stephen Anton, Ph.D., division chief of clinical research for the department of aging and geriatric research, who was not involved in the research.
Part of the reason could be that when people walk, they use glucose to fuel that movement, Anton said. Not using that glucose could cause an imbalance between the amount of glucose in the body and the body’s ability to use insulin to process that glucose, resulting in diabetes. Manini said standing or walking five minutes for each hour spent sitting could help mitigate the effects of sitting, but more research is needed to learn what amount of movement will be effective.
“The study informs us that healthy lifestyle is not simply exercising 30 minutes a day and eating healthfully, but also paying attention to how inactive you are throughout the day,” Anton said.