Insulin is the pancreatic hormone that escorts glucose, a simple sugar, into the body's cells to supply energy. When cells become overwhelmed dealing with excess glucose, they become resistant to insulin. This can happen when there is too little physical activity relative to the number of calories consumed, because of a diet high in excessive simple sugar, or because of abdominal obesity.
Sedentary Lifestyles
Consuming calories in excess of the body's energy needs leads to insulin resistance. Until the advent of the automobile this was rare, because walking as a primary means of transportation uses 500 calories for every five miles or 10,000 steps a day. For millions of years, men and women spent most of every day hunting and gathering food; very active ways of putting food on the table. Only a few groups of people do that much walking today, including the Old Order Amish, says David Bassett, Ph.D., from the University of Tennessee, who gave Amish men and women pedometers and measured their daily step counts. In the January 2004 issue of the journal "Medicine and Science in Sports and Exercise," Bassett noted that Amish men averaged over 18,000 steps a day and women more than 14,000. This level of activity meant that none of the Amish men Bassett studied were obese and only 9 percent of the women battled this cause of insulin resistance despite a diet high in calories.
Having become a sedentary society also appears to influence insulin resistance in a more direct way, according to the work of British researchers writing in the August 2009 issue of "Diabetes." Hendrik J.F. Helmerhorst, M.D., and his team demonstrated that the percentage of wake time spent in physical activity was more important than bursts of physical exercise in preventing insulin resistance blood indicators.
Excessive Simple Carbohydrates
Insulin resistance can be overwhelmed by excessive intake of simple carbohydrates in the form of soda; juice; and products made with wheat, sugar or white rice. These foods are low in fiber and highly processed so they arrive in the body ready for immediate digestion. The portion size of these foods is often excessive in the standard American diet, according to a review by "Harvard Magazine" health journalist Craig Lambert, Ph.D., in the May 2004 edition. In contrast, vegetables, whole unprocessed grains and whole fruits deliver many nutrients and fiber. Eating them in moderate portions does not excessively raise the demand for insulin, helping to maintain normal insulin sensitivity of the body's cells.
Abdominal Obesity
A healthy weight is defined for adults as a body mass index of 18.5 to 24.9. But not all people at a healthy weight are free from insulin resistance risk and not all people with a BMI in the overweight category, 25 to 29.9, may be at equal risk of insulin resistance.
Where the weight is carried matters, as demonstrated by a research team in Valencia, Spain, writing in the March 2003 issue of the "European Journal of Internal Medicine." The researchers used the World Health Organization's definition of abdominal obesity---34.45 inches for women and 43 inches for men---and found that those who met these criteria had a risk of insulin resistance 259 percent higher than those with healthy waist measurements.
References
- "Medicine and Science in Sports and Exercise"; Physical Activity in Old Order Amish; David Bassett, Ph.D., et al.; January 2004
- "Diabetes"; Objectively Measured Sedentary Time May Predict Insulin Resistance; Hendrik J.F. Helmerhorst et al.; August 2009
- "Harvard Magazine"; The Way We Eat Now; Craig Lambert, Ph.D.; May-June 2004
- "American Journal of Clinical Nutrition"; Whole-Grain Intake and Insulin Sensitivity; A.D. Liese et al.; November 2003
- "European Journal of Internal Medicine"; Abdominal Obesity, Insulin Resistance and Metabolic Syndrome; J.F. Ascaso, M.D., et al.; March 2003
