Good insulin sensitivity is important for metabolic health. When it goes down, a condition called insulin resistance, your pancreas has to produce more insulin because your cells are less responsive to it. This places extra stress on your pancreas and increases the risk that your pancreas will “burn out,” leading to type 2 diabetes.
A decline in insulin sensitivity makes it easier for your body to store fat. How so? All of the insulin floating around in your bloodstream makes it harder for your body to mobilize stored fat and use it for energy. In addition, it creates conditions that are ripe for other health problems including heart disease and fatty liver.
One factor that affects insulin sensitivity is age. As we age, insulin sensitivity declines. That’s one reason the risk of type 2 diabetes and metabolic syndrome goes up after middle-age. It also partially explains why people gain body fat, especially deeper abdominal fat called visceral fat. The question is whether this change is due to the aging process itself or a reflection of changes in body composition with age i.e. gains in body fat. How much control do you really have over how your cells respond to insulin as you age?
Insulin Sensitivity and Aging
According to a study published in the journal Diabetes, the decrease in insulin sensitivity that occurs with age is a reflection of changes in body composition rather than the aging process itself. As we age, we lose muscle and have and put on more body fat. As body fat percentages go up, insulin sensitivity goes down. This makes it even harder to maintain a healthy weight and body composition. It’s a vicious cycle that makes weight control challenging. But based on this study, aging is not the cause of decreased insulin sensitivity – changes in body composition that occur with age are. That’s good news since body composition is something you have more control over.
According to a study published in Sports Medicine, regular aerobic and resistance exercise helps to maintain insulin sensitivity with age. One way it does this is by reducing gains in body fat, particularly visceral fat, which is so common as we age – but exercise has a direct effect on insulin sensitivity as well.
How does exercise increase insulin sensitivity? During exercise, cells are able to take up glucose independently of insulin. Normally, insulin is required to unlock the cellular gates that let glucose into cells. During exercise, glucose is able to enter muscle cells without the assistance of insulin. In addition, as other studies show, exercise directly increases insulin sensitivity. One way exercise does this is by activating an enzyme called AMPK that increases insulin sensitivity. AMPK has other desirable effects too – it stimulates fat breakdown. In fact, insulin sensitivity is higher for up to 16 hours after a single exercise session. Which type of exercise is best? According to this study, aerobic exercise and resistance training are both equally effective.
There’s more good news. Individuals who are more physically fit have even greater improvements in insulin sensitivity after exercise. Studies also show that the increase in sensitivity associated with exercise is enhanced even more by weight loss. Two of the best things you can do to avoid insulin resistance as you age is to maintain healthy body weight and a healthy body fat percentage – and exercise.
Other Ways to Improve Insulin Sensitivity
Make sure you’re getting your zzz’s. Even one night of sleep deprivation significantly decreases insulin sensitivity. It also alters leptin and ghrelin levels so you feel hungrier. Sleep is important not only for insulin sensitivity but for overall health and weight control.
The composition of your diet has an impact too. Eating a diet of processed food and rapidly absorbed carbs fuels insulin resistance and creates a pro-inflammatory state that puts you at greater risk for metabolic syndrome, type 2 diabetes, and heart disease. Processed foods frequently contain high-fructose corn syrup, a controversial sweetener that aggravates insulin resistance according to some research. One study showed a Mediterranean diet, rich in fruits, vegetables, fish and heart-healthy fats helps to increase insulin sensitivity.
The Bottom Line?
Insulin sensitivity declines with age but it seems to be related to changes in body composition rather than an inevitable consequence of aging. Fortunately, there are things you can do to maintain good insulin sensitivity and avoid the problems associated with insulin resistance. Aerobic and resistance training both improve insulin sensitivity when you do them regularly. Combine exercise with a diet consisting of unprocessed foods and plenty of sleep and you have the recipe for better insulin sensitivity and a better body composition too.
References:
Diabetes 2010, January: 59(1): 89-97.
Sports Med. 2000. Nov: 30(5): 327-48.
Adv Exp Med Biol. 1998;441:1-16.
Medscape. “Exercise: How Does It Promote Insulin Sensitivity?”
Int J Sports Med. 2000 Jan;21(1):1-12.
Am J Clin Nutr November 2002 vol. 76 no. 5 911-922
Diabetes Care March 2003 vol. 26 no. 3 944-945.
Medscape Family Medicine. “Insulin Sensitivity Improved With Mediterranean-Style Diet”
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