Insulin sensitivity and insulin resistance
Your metabolic health depends, in large part, on your body’s ability to maintain blood sugar (glucose) levels in a relatively narrow range. And when blood sugar rises above the healthy upper limit, as happens after a meal, to bring blood sugar back into the healthy range in short order. The hormone, insulin, regulates blood sugar. Insulin sensitivity refers to how well the body responds to insulin, such that it can escort blood sugar molecules into muscle and other types of cells. However, a heavy diet of junk food can thwart the ability of insulin to transport blood sugar into cells. This condition is called insulin resistance. Aspects of diet, exercise, and sleep affect insulin sensitivity.
Advanced glycation end products
High heat-driven reactions between sugars, fat molecules, and proteins, and nucleic acids create advanced glycation end products (AGES). They comprise the brown material in a crust of bread or in toast. Animal and human studies show that increased consumption of AGEs predicts decreased insulin sensitivity and possibly higher risk of type 2 diabetes. Researchers in Australia designed a clinical trial that used the gold standard for measuring insulin sensitivity. Participants included twenty overweight men and women with an average age of 34 years. All participants ate a diet either high or low in AGEs for two weeks followed by a 4-week washout period followed by two weeks of the other AGE diet. The two diets were otherwise matched in terms of macronutrient composition. The two-week diet of low AGEs resulted in significantly greater insulin sensitivity compared to the high AGEs diet. This in spite of the fact that the high AGEs diet was not that much higher in AGEs (about 50 percent) that the low AGEs diet.
Eat meat and veggies first
Clinical studies show that ingesting vegetables and/or protein before carbohydrates in a meal leads to lower blood glucose and blood insulin responses during three hours following the meal. But would similar results occur with type 2 diabetics under free-living conditions? Researchers in Italy recruited 17 volunteers who consumed either an experimental or a control diet for 8 weeks. Both diets limited calorie intake slightly (by about 200 calories per day) and were similar in other respects, except that participants in the experimental diet group were asked to eat meat first followed by vegetables, bread or pasta, and fruit. Over 8 weeks, participants in both groups lost about one kg of body weight and 3 cm of waist circumference. Only participants in the experimental diet group showed significant declines in HbA1c (-0.3 percent), fasting blood glucose (-18.0 mg/dL), and increases in post-meal blood glucose (-32.4 mg/dL for lunch and 18.0 mg/dL for dinner). Compared to the control diet, the experimental diet led to significantly lower post-meal blood glucose increases and more stable blood glucose levels. Altering the sequence of food intake improved post-meal blood glucose and insulin conditions for type 2 diabetic persons.
Get plenty of sleep
Insufficient sleep predicts increased risk of type 2 diabetes. But how does insufficient sleep affect persons with newly diagnosed diabetes? Researchers used data from 365 participants with type 2 diabetes diagnosed 5-8 months prior to the start of the study in the Early ACTivity in Diabetes randomized controlled trial to find out. At baseline, weekday sleep debt (getting less sleep on average during the week compared to the weekend) was linked to significantly higher body weight, body-mass index, waist circumference, and HOMAR (a measure of insulin resistance). At 6 months post-baseline, weekday sleep debt predicted significantly increased risk of obesity, waist circumference, insulin resistance, and HbA1c. As little as 30 minutes of weekday sleep deficit may contribute to new or continued obesity, increased waist circumference, and insulin resistance in persons with new type 2 diabetes.
Brisk walking
There seems to be some confusion regarding the inevitability of aging for older adults. Distinguishing between primary aging and secondary aging can resolve the dispute. Primary aging refers to progressive and seemingly inevitable bodily deterioration during adulthood. Secondary aging refers to deterioration that arises from diseases and poor lifestyle choices. Much of secondary aging can be reduced or postponed with better lifestyle choices. Exercise can thwart secondary aging by maintaining mitochondrial function and muscle mass. Both physical activity (related to the performance of daily activities) and exercise (planned activities to improve body condition) can increase longevity, and, more importantly, increase quality of life. Insufficient bodily movement leads promotes a host of undesirable bodily changes, including muscle atrophy, loss of muscle mass, fat accumulation, reduced insulin sensitivity, impaired glucose tolerance, and type 2 diabetes. Loss of muscle mass is associated with major functional decline and increases in disability and dependence.
Happily, 67-year old women who walked briskly for one hour showed increased insulin sensitivity the following day. Talk about quick results! Endurance exercise performed three to five times weekly can improve insulin sensitivity and reduce body fat in just a few weeks. Unhappily, two-thirds of Americans aged 60-74 exhibit the combined prevalence of diabetes (mostly type 2), excess blood glucose levels, and impaired glucose tolerance. The prevalence rises to three-quarters for 75-year old Americans. These data imply a looming public health disaster, given prediction that Americans over age 65 will account for half the US population in the next decade. On the other hand, you can take a different path of daily brisk walking or engaging in other forms of regular physical activity.
Regular exercise
Health authorities recommend that adults with type 2 diabetes engage in moderate or vigorous intensity aerobic exercise 3-5 times per week. Adding a program of progressive resistance training provides even more benefits. A key marker of type 2 diabetes is insulin resistance. Exercise improves insulin sensitivity. Researchers in the UK conducted a systematic review and meta-analysis of 14 randomized controlled trials of middle-aged participants with type 2 diabetes to determine the length of time that regular exercise increases insulin sensitivity. Analysis showed that exercise significantly improved insulin sensitivity compared to control groups for data pooled across the individual studies. Additional analysis showed that the positive effect of exercise on insulin sensitivity persisted for at least 72 hours (three days) following the last bout of exercise. Thus, persons with type 2 diabetes who exercise regularly (nearly every day) might maintain high insulin sensitivity and thereby maintain blood sugar in a healthy range.
What to do
If you eat a high-quality diet, get plenty of regular and restful sleep, ramp up your level of exercise, you’ll probably maintain high insulin sensitivity, keep your blood sugar under control, and reduce your risks of chronic diseases, especially type 2 diabetes.
