Recent clinical trials and ongoing studies have emphasized the importance of physical activity or combined physical activity and improved diet in the prevention of type 2 diabetes.
LSU AgCenter nutritionist Dr. Heli Roy says exercise training studies have demonstrated improvements in insulin sensitivity after individual exercise bouts and after a series of training sessions. However, the ideal exercise regimen to improve insulin sensitivity in diabetic and non-diabetic individuals is not known.
A study by doctors Tuomo Rankinen and Claude Bouchard from the Pennington Biomedical Research Center, together with other researchers, determined the effects of a 20-week endurance training program on insulin sensitivity, insulin secretion and other variables while considering sex, race, age and BMI (body mass index) as well as changes in adiposity (obesity) and physical fitness in individuals. In addition, the effects of regular exercise on fasting insulin and glucose concentrations measured 24 and 72 hours after the last exercise session were considered.
The study was part of a multi-center HERITAGE Family Study. The main objective of the HERITAGE (HEalth, RIsk factors, exercise Training And GEnetics) study was to assess the role of genetic factors in cardiovascular, metabolic and hormonal responses to aerobic exercise training in sedentary families.
The analyses included 316 women (109 blacks and 207 whites) and 280 men (64 black and 216 whites). The subjects participated in an exercise training program for 20 weeks.
Results revealed that after the training program, both body weight and waist circumference dropped significantly. Insulin sensitivity in all groups improved significantly as well. However, men improved more significantly in insulin sensitivity than women, and blacks improved more significantly than whites. Normal-weight subjects had smaller improvement than overweight or obese participants. Insulin sensitivity improved with weight loss and reduction in waist circumference.
Roy says the principal finding of this study was that structured regular exercise leads on average to beneficial effects on insulin sensitivity. The magnitude of the changes, however, varied considerably. Regardless of race, men had larger improvements in insulin sensitivity than women, and participants with the lowest glucose tolerance had an increase in insulin secretion.
Changes in insulin sensitivity were not associated with the initial body mass or age of participants. Improvements in fasting insulin, however, were no longer present 72 hours after the last exercise period.
Roy says these results show that a regular exercise program is required to sustain the improvements in insulin sensitivity. The present results also suggest that adding exercise to other weight loss interventions could improve glucose tolerance while diminishing the risk of low glucose values.
For additional information, please visit the Food & Health section of the LSU AgCenter Web site. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.
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