BRIDGING THE GAP
RESEARCH and PRACTICALITY
Exercise and Nutrition for Type II Diabetes Mellitus Patients
Type II diabetes mellitus (T2DM) is a metabolic disorder resulting from insulin resistance and leading to glucose intolerance. The disease is primarily a result of unhealthy lifestyle factors, such as a lack of activity and an unhealthy diet (1). T2DM is typically found in obese and overweight patients. Over eighty percent of T2DM patients are clinically obese due to the onset of unhealthy lifestyle factors (2). There are two main factors of diabetes: insulin insensitivity and glucose intolerance (1). Insulin insensitivity occurs when the insulin receptors on the peripheral cells do not respond to insulin effectively. Insulin is responsible for the transport of glucose from the blood into peripheral cells, primarily muscle and adipose cells. Glucose that is transported into peripheral cells is used to produce energy. In muscle fibers, excess glucose can be stored as glycogen, while in adipocytes the glucose is converted and stored as lipid. Glucose intolerance results from insulin insensitivity and is characterized by excessively, and dangerously, elevated blood glucose levels. High blood glucose levels are fasting levels above 126 mg/dL or a random blood glucose level of greater than 200 mg/dL (3). Diabetic patients with insulin resistance and glucose intolerance will have high blood glucose levels, which can lead to additional co-morbidities such as hypertension, dyslipidemia and atherosclerosis (1). Lowering a personís blood glucose levels reduces their chances of developing additional co-morbidities, improves overall functional capacity and prolongs mortality (4).
Medical treatments to control blood glucose in type 2 diabetics include numerous pharmacological approaches ranging from slowing glucose absorption in the intestine to insulin sensitizers in peripheral tissues (5). Because T2DM patients have hyperinsulinemia due to their insulin resistance, medications alone often do not completely control patientís blood glucose levels. Research has shown that exercise and dietary modifications can help treat, and often prevent the development of diabetes through insulin-independent means (6).
Exercise has been found to significantly decrease blood glucose levels during and after exercise (7). A study on T2DM patients found that after high intensity interval training (HIIT), the average decrease of blood glucose after HIIT exercise was about 1 mmol/L (6). HIIT exercises are brief intervals of high intensity exercise (often 30 seconds in duration) followed by an interval of low intensity exercise or rest. Intensity of exercises can be measured with percentage of VO2max levels or with percent of heart rate max levels. Not only was HIIT exercise found to lower blood glucose levels for the period immediately after exercise, but HIIT lowered blood glucose levels for the rest of the day, including in some studies even after meals for up to 78 hours (7). Both interval and continuous exercises will help lower and control blood glucose levels. Another study found that HIIT exercises not only lowered blood glucose levels (independent of insulin due to increased muscle uptake) but also lowered HbA1C levels (6). HbA1C levels give an indication of a patientís blood glucose over a two-to-three-month time period. Researchers have shown that both continuous and interval exercise can lower body fat percentages and reduce systolic blood pressure: two co-morbidities of T2DM (6). Lowering body fat and blood pressure leads to a decreased risk profile, while also lowering blood glucose levels. Thus, exercise is an important component for a patient with T2DM to supplement into their lifestyle. Exercise, specifically HIIT exercise, will reduce the need for insulin secretion which allows the beta cells of the pancreas to be less stressed, produce lower insulin levels, and remain healthy and functional (2).
Stuart and colleagues found that skeletal muscle GLUT-4 glucose transporters increased directly after high intensity training in fast twitch muscle fibers only (8). Fast-twitch muscles are used in higher intensity exercises like HIIT exercises. They also found that after two weeks of low intensity training, slow-twitch muscle fibers began to show increased levels of GLUT-4 receptors (8). With progressive training, muscle cells can adapt to intake more glucose by adding more GLUT-4 transporters on muscle fibers. GLUT-4 transporters are stimulated to increase transport because of activity or exercise causing transport glucose into muscle cells independent of insulin and are an important component responsible for a non-insulin means of lowering blood glucose levels.
Carvalo found that GLUT-4 protein levels increased by 50% for 16 hours after an initial exercise bout and GLUT-4 concentration doubled after two days of exercise (9). An increase in GLUT-4 concentration is due to the muscle fibersí added need of glucose for energy. With more GLUT-4 transporters in the plasma membrane of muscle cells, more of the absorbed glucose will enter the muscle fibers than entering the adipocytes. This gives more opportunity for blood glucose levels to be lowered effectively without the use of insulin and without adding body fat stores.
Overall, the American Medical Association in conjunction with the American College of Sports Medicine recommend patients with T2DM to add exercise to their lifestyles in order to lower blood glucose by insulin-independent means. Exercise should be implemented in a T2DM patientís daily regimen whether the individual chooses a more demanding workout with HIIT exercises, or chooses to follow the AMA/ACSM Guidelines of resistance exercise: 2-3 days per week and cardiovascular exercise 3-5 days per week, and daily physical activity including up to 10,000 steps per day most days of the week. This increased activity level will help maintain functional capacity, reduce morbidity, and extend mortality. Overall, research has proven exercise to be an effective, non-pharmacological means to lower blood glucose levels, while reducing co-morbidities.
Nutrition, fitness and over all wellness are important factors to consider when treating for chronic lifestyle diseases. Nutrition is a critical component of any clinical care plan and is instrumental in treatment and prevention of lifestyle diseases. Co-morbidities of T2DM include, obesity, cardiovascular disease, and cancer (4). A diet that can combat these co-morbidities while treating T2DM is a whole food plant-based diet (WFPD). The diet consists of foods solely from plant-based sources like fruits, vegetables, whole grains, and legumes. A WFPD will eliminate meat and any other animal based foods (10). Eliminating animal based foods will eliminate cholesterol from the diet. It is important to eliminate cholesterol from the diet for T2DM patients because having a high blood cholesterol level is a main indicator for developing co-morbidities such as atherosclerosis (600-11). Atherosclerosis is caused by plaque build-up in blood vessels, which is promoted by high blood cholesterol and blood lipid levels. WFPD will also increase the amount of fiber in the diet. Water-soluble fiber can bind to and extract cholesterol and lipid from the digestive system to lower cholesterol levels. Along with the reduction of blood cholesterol, an increased intake of fiber will help to lower blood glucose levels. By replacing simple carbohydrates with complex carbohydrates that are commonly found in a WFPD, post-prandial blood glucose spikes will be more controlled. Complex carbohydrates have lower glycemic indexes than simple carbohydrates. Glycemic index is a value from 1 to 100 of how a 50-gram sample of food will raise blood glucose levels in comparison to pure glucose; a glycemic index value of 100. It is important for T2DM patients to choose foods with lower glycemic indices for an example: White bread has a glycemic index of 75 while 100% whole wheat bread has a glycemic index of 51 (12). Simple carbohydrates like sugars will have a high glycemic load while more complex carbohydrates will have lower glycemic loads (13). Complex carbohydrates are carbohydrates that take longer to digest and are found in foods with higher fiber content (14). Common carbohydrates with low glycemic loads are foods such as beans, lentils, whole-grains, bran and leafy greens (14). Being on a WFPD and choosing foods with lower glycemic indices is important for the treatment of T2DM. It is important to reduce the risk of developing co-morbidities with a WFPD and to treat T2DM with choosing low glycemic indices foods (13). With the combination of exercise and proper nutrition, T2DM patients can see significant results through noninsulin means.
Not only is the content of food important in the diet of a person with T2DM, but planning the time that the patient eats will help to treat the disease as well. A clinical study observed the difference of blood glucose levels pre and post-prandial in T2DM patients (15). Volunteers either walked at a moderate intensity directly before, or 20 minutes after their meal period. Blood glucose levels were about 3 mmol/L lower in the group that walked 20 minutes after their meal than walking directly before their meal (15). The group who walked postprandially also had lower blood glucose that stayed significantly reduced for 90 minutes post-exercise (15).
T2DM patients should eat foods within a WFPD that have lower glycemic indices and do a spout of a 20-minute continuous exercise post-prandial to optimize lowering blood glucose levels by insulin-independent means.
Type II Diabetes Mellitus patients can greatly supplement their insulin medications with proper exercise and nutrition. For reductions in drug side-effects and costs it is important for T2DM patients to become less dependent on their medications. This can be done with postprandial exercise and supplementing their lifestyle with HIIT exercise. With the combination of HIIT exercise, exercising after meals, and eating foods with a lower glycemic index, T2DM patients can get their blood glucose levels down significantly through insulin-independent means and reduce the risk of developing co-morbidities.
Written by Emily Hamocon with Eric Sternlicht, Ph.D., Chapman University, Orange CA.
6. Mitranun, W., Deerochanawong, C., Tanaka, H., & Suksom, D. (2013, July 26) Continuous vs interval training on glycemic control and macro- and microvascular reactivity in type 2 diabetic patients. Scandinavian Journal of Medicine and Science in Sports, 24, 69-76. doi:10.1111/sms.12112
7. Little, J. P., Gillen, J. B., Percival, M. P., Sandra, A., Tarnopolsky, M. A., Punthakee, Z., . . . Gibala, M. J. (2011, December). Low-volume high-intensity interval training reduces hyperglycemia and increases muscle mitochondrial capacity in patients with type 2 diabetes. Journal of Applied Physiology, 111, 1554-1560. doi:10.1152/japplphysiol.00921
8. Stuart, C. A., Howell, M. E., Baker, J. D., Dykes, R. J., Duffourc, M. M., Ramsey, M. W., & Stone, M. H. (2010, January). Cycle Training Increased GLUT4 and Activation of Mammalian Target of Rapamycin in Fast Twitch Muscle Fibers. Medicine & Science in Sports & Exercise, 42(1), 96-106. doi:10.1249/mss.0b013e3181ad7f36
9. Carvalho, E. (2001) Insulin resistance with low cellular IRS-1 expression is also associated with low GLUT4 expression and impaired insulin-stimulated glucose transport. The Journal of Biological Chemistry, 269(20), 14396-14401. doi:10.1096/fj.00-0435fje
15. Colberg, S. R., Zarrabi, L., Bennington, L., Nakave, A., Somma, C. T., Swain, D. P., & Sechrist, S. R. (2009). Postprandial Walking is Better for Lowering the Glycemic Effect of Dinner than Pre-Dinner Exercise in Type 2 Diabetic Individuals. Journal of the American Medical Directors Association, 10(6), 394-397. doi:10.1016/j.jamda.2009.03.015