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Activity of Any Kind Improves Insulin Sensitivity

Posted: Thursday, September 27, 2007

Total activity -- or more accurately, the lack of it -- appears to be a major driver of insulin resistance, a key component of the metabolic syndrome and a cardiovascular risk factor. 
Baseline data from a prospective study of normal, healthy adults in 19 European centers indicated that those who were most active during a typical day had significantly lower levels of insulin resistance irrespective of waist-to-hip ratio, reported Mark Walker, M.D., of the University of Newcastle-Upon-Tyne in England, on behalf of colleagues in the RISC study.
Dr. Walker discussed preliminary findings from the ongoing longitudinal RISC (Relationship between Insulin Sensitivity and Cardiovascular Risk) study at the meeting of the European Association for the Study of Diabetes.

"Insulin resistance is not the sole driver of cardiometabolic risk, but obesity, and particularly central obesity and high circulating insulin levels also contribute," said Dr. Walker.

Most telling, however, was the relationship between total accumulated activity, as measured by accelerometers, and decreased insulin resistance.

"Total physical activity is the key determinant of insulin sensitivity," he said. "What we would say from this is even if you have an office job, if you sit around a lot of the day, if you then go out and increase your total activity by doing a period of swimming or cycling, that's good, as long as you get your total activity up, you have a positive association with insulin sensitivity."

 
Increasing total activity by other means, such as taking the stairs when possible or walking to work can also significantly reduce the risk of insulin resistance and associated cardiovascular risk, he added.
And the benefit was apparent regardless of central adiposity, which is considered a driver of insulin resistance.
Total activity levels were also inversely associated with carotid artery stiffness. There was not, however, an association between carotid intimal thickness and activity levels.
 
A total of 1,338 healthy adult volunteers recruited at 14 centers in 19 European countries underwent euglycemic clamp testing, which measures insulin resistance by balancing insulin infusions with glucose infusions and monitoring the result. The volunteers also had oral glucose tolerance tests to calculate their total insulin exposure.
The study excluded patients with risk factors that were either known or detected at screening, including diabetes, hypertension, dyslipidemia, cardiovascular disease, pulmonary disease, renal disease, or cancer within the last five years.
They measured activity in a subset of 807 volunteers, who were equipped with accelerometers that measured most daily activities, ranging from rigorous activity (such as aerobic exercise) to mild activity (such as fidgeting).
The authors found that at baseline, body mass index was associated with all cardiovascular risk factors, including hypertension and unfavorable lipid profiles. They also found positive associations between waist circumference (as measured by waist-to-hip ratio), lower HDL, elevated triglycerides, and higher blood pressure.

When they looked at insulin sensitivity, they found that it was positively associated with postprandial free-fatty acids, triglycerides, and LDL, and negatively associated with HDL. Insulin exposure was linked to higher heart rates, blood pressures, and fasting plasma glucose, and worse lipid parameters.

 
The authors also found that insulin resistance and hyperinsulinemia could be detected as independent factors rather than as inevitable companions. When they looked at insulin sensitivity by quartile in both men and women, they saw that as insulin resistance increased so, too, did cardiovascular risk score, insulin exposure, waist circumference, and BMI.
Additionally, in a multivariate analysis carried out by RISC project coordinator Erle Ferranini, M.D., of the University of Pisa, in Italy, the investigators found that insulin exposure, waist circumference, and BMI were all independent predictors of cardiovascular risk score.

But the authors also found that, in a three-year follow-up study of 708 patients, 1% had developed diabetes, 8% developed impaired fasting glucose, 12% had developed impaired glucose tolerance, 13% developed hypertension, and 11% developed central adiposity.

Preliminary analyses of the follow-up data suggest, "impaired pancreatic beta cell function is associated with an almost threefold risk of developing abnormal glucose tolerance and diabetes, and also a twofold risk of developing or contributing to abdominal obesity," Dr. Walker said.

 
Finally, Dr. Walker said, the key question as to whether insulin resistance at baseline can independently predict cardiovascular disease as measured by carotid intimal thickness will have to wait until completion of the study in 2017.
Practice Pearl: Explain to patients that insulin resistance is believed to be a major risk factor for cardiovascular disease, and this study suggests that activity of any kind can help to improve insulin sensitivity, even among people with abdominal obesity

Source: Diabetes In Control: European Association for the Study of Diabetes Annual Meeting: "Insulin resistance, cardiovascular risk, and physical activity in a European population: the RISC Study." Presented at a briefing Sept. 19 and in formal session Sept. 21.

 
 
 
 
 
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