
What is insulin resistance?
Insulin is a hormone produced in the pancreas, and released in response to elevated blood sugar levels (also called blood glucose levels). It helps to transport digested carbohydrates and sugars into body tissues such as muscle and fat for energy production and storage.
Due to a range of genetic and lifestyle factors (such as inactivity and an unhealthy diet), the body can become resistant to insulin. The body still produces insulin, but it isn't used well, so extra insulin is needed to regulate blood sugar levels. This places stress on the body, and may increase the risk of lifestyle disease. It is difficult to know if you are insulin resistant without a blood test, although excess body fat and fatigue may be an indication.
What is the link between insulin resistance and body fat?
Insulin's role in transporting nutrients out of the blood stream for storage is not only limited to sugars (glucose). Insulin also encourages the storage of dietary fats as body fat. People who are insulin resistant have a higher level of insulin circulating in their blood compared to someone who is more insulin sensitive. Excess weight is thought to be a major contributor to insulin resistance, particularly excess body fat around the waist.
The research
A study published in the American Journal for Preventative Medicine examined the effects of dietary weight loss and exercise on insulin sensitivity. The 12 month study involved 439 inactive, overweight postmenopausal women who were randomly assigned to 1 of 4 groups, including:
At the study's completion, significant improvements in insulin sensitivity were detected in the diet, and the combined diet and exercise group, but not in the exercise only or control groups. The magnitude of weight loss determined the level of improvements in insulin sensitivity. The benefits of these lifestyle modifications were similar in both middle-aged and older women. While no overall improvement in insulin sensitivity was detected in the exercise only group, they still experienced significant reductions in waist circumference and body fat, and saw improvements in impaired blood glucose regulation.
How to prevent insulin resistance?
It seems that a healthy body is likely to be more sensitive to insulin. A good diet combined with exercise, and healthy level of body fat seems like the safest and most effective ways to prevent insulin resistance. Following are some important practical implications from this research.
References available on request