Can Resistance Training Help to Combat Type 2 Diabetes?
The human body is an incredible machine. In fact, it’s likely the most sophisticated piece of machinery ever created, and with each passing generation, the human race finds new ways to push the boundaries of its physiology, constantly seeking ways to make itself bigger, stronger, faster, and smarter.
Yet, despite these incredible feats, if recent history is any indication, human beings might be the engineers of their own demise.
Related - Strength Training Fights Type 2 Diabetes?
The prevalence of obesity, type 2 diabetes and prediabetes is rapidly increasing. This is bolstered by recent estimates which indicate that over 66% of the population is overweight and/or obese and ~10% is diabetic (90-95% being Type 2 diabetic). [2,3] And, another third of U.S. adults are prediabetic and 90% don’t even realize it. 
If your family is similar to mine these stats hit very, very close to home, meaning there’s more than one family member affected by one (or more) of these conditions, and you’ve lived a considerable portion of your life seeing family and friends live in these dysfunctional states.
I can tell you personally, it flat out sucks, and try as we might to help, the advice usually goes unheeded.
My journey into this career as a writer, consultant, and supplement nerd was catalyzed by the death of my grandfather, which was brought on by a lifetime of neglected health (smoking, drinking, etc) as well as seeing my own father’s (and uncle’s) health slowly decline due to poor eating habits and lack of physical activity which culminated in both getting type 2 diabetes.
Now, truth be told, my father has gotten better about managing his condition over the past few years, but if he (and millions of others) had incorporated what I’m about to cover in great detail ahead, maybe they all would be a bit better off than they are now. And, in the case of my grandfather and uncle, they might still be alive.
So, this hits home for me, and I’m sure for some of you reading this it does too.
But, enough blathering about society’s sad state. Let’s get on to what can be done to remedy the situation.
Mounting the Attack Against Type 2 Diabetes
Type 2 diabetes is a condition characterized by an inability to properly metabolize glucose either from an inability to secrete insulin or use it efficiently (a.k.a. Insulin resistance).
In case you need a refresher, insulin is a peptide hormone secreted by beta cells in the pancreas that regulates blood sugar levels. When the concentration of sugar rises, insulin shuttles glucose out of the blood and into muscle cells and adipose tissue. But that’s not all insulin does (despite what the paleo and keto zealots would have you believe).
Insulin also serves vital roles in the metabolism of proteins and fats. In fact, here’s an extensive list of insulin’s multi-faceted roles in the body: Protein Metabolism
- Increases the transport of amino acids in cells
- Increases muscle protein synthesis rates
- Decreases protein degradation rates in muscle
- Decreases the rate of lipolysis in adipose tissue (thereby lowering plasma fatty acid concentrations)
- Stimulates fatty acid synthesis in tissues
- Increases uptake of triglycerides from the blood into muscle and adipose tissue
- Decreases the rate of fatty acid oxidation in muscle and liver cells
Now, when you become a type 2 diabetic your body either stops producing insulin or your cells become resistant to it, which means sugar cannot make its way from the blood into your cells, leading to the two-fold problem of excess glucose in the blood (hyperglycemia) and an inability of your cells to use glucose for energy.
As a result of this high blood sugar, a number of issues arise that can cause serious health problems, including cardiovascular disease, kidney disease, and loss of vision. [8,9]
It’s commonly advised to utilize a mixture of prescription medication (i.e. metformin, exogenous insulin, etc), dietary changes, and increased physical activity (usually in the form of aerobic training -- “cardio”) in the treatment of type 2 diabetes.  The issue is with this is that only ~25% of adults aged 18 and over meet the Physical Activity Guidelines. 
And let’s be frank, even the people that enjoy being physically active typically hate cardio as its typically performed (long, slow boring running or jogging on a treadmill), for the sheer reason that it’s incredibly boring.
But there’s also this to consider -- aerobic training doesn’t do much to build muscle and the more frequently you perform the same type of aerobic training, the more efficient your body becomes at performing it, meaning you expend less energy, tax your muscles less, and burn fewer calories.
Yes, aerobic training is good for overall cardiovascular health and should be included as part of all training programs, but as for it being the sole means of exercise for combating the progression of type 2 diabetes, I think it’s inferior.
And here’s why…
Lift Weight to Combat Type 2 Diabetes
When a person presents with metabolic syndrome, type 2 diabetes or some other form of chronic disease brought on by poor diet and physical inactivity, the good old doctor recommends eating better and increasing physical activity.
Aerobic training has long been viewed as the ideal form of exercise for improving glucose control. And there’s no disputing that it can help improve insulin sensitivity and the body’s ability to handle sugar.
But is it the most effective means?
According to the latest research, aerobic training might not be the most optimal method.
A host of recent studies are showing that resistance training, not aerobic training, may be more optimal. This is highlighted by a randomized control trial from 2005 involving 43 individuals with type 2 diabetes had them perform either resistance training or aerobic training for 4 months and tracked a number of diabetes-related markers including A1C and fasting blood glucose. 
After 4 months of regular training, researchers documented that A1C was significantly reduced with resistance training but not aerobic training. Additionally, both insulin resistance and fasting blood glucose decreases and lipid profile improved in subjects performing resistance training but not aerobic training.  Other aerobic exercise trials have also shown little effect on blood glucose control as determined by HbA1c. 
Evidence from other randomized controlled trials has shown that resistance training improves glycemic control in patients with type 2 diabetes, increases glucose disposal, and even improves the risk profiles of lipid and cardiovascular disease in patients with type 2 diabetes. [11,12]
Additionally, the Health Professionals Follow-up Study examined the association of resistance training as the primary prevention of type 2 diabetes in men and found a 34% lower risk of type 2 diabetes, INDEPENDENT of aerobic exercise. 
More recently, a 2019 meta-analysis of 20 studies (including data from over 800 subjects) which showed an average 0.5 decrease in HbA1c scores in type II diabetics who underwent a resistance training program. 
Furthermore, researchers found a significantly greater decrease in HbA1c scores and insulin with higher intensity resistance training vs. low to moderate intensities, striking yet another victory for the lift heavy crowd over the light weight, high rep pump fiends.
Again, aerobic training is successful at improving glucose control, insulin sensitivity, endothelial function, lipid profile, and other cardiovascular risk factors, but it’s not enough on its own. [15,16,17,18]
You see, skeletal muscle is the largest reserve the body has to dispose of glucose and triglycerides. However, the amount of skeletal muscle mass an individual has dropped at a rate of 3-8% each decade after age 30.  This is part of the reason our ability to handle glucose (carbs) declines with age, thereby increasing the potential for becoming a type 2 diabetic.
Other unwanted consequences of decreasing muscle mass are:
- Lower resting metabolic rate
- Reduced capacity for fat oxidation
- Decreased glucose uptake
- Shorter life span (epidemiological studies find an inverse relationship between the amount of muscle and strength a person has and all-cause mortality) 
Additionally, the ability of skeletal muscle to metabolize fat is impaired leading to a buildup of lipids in muscle cells, which leads to complications with insulin signaling within the cell, contributing to further insulin resistance. 
Resistance training (even a single bout), however, increases triglyceride plasma clearance rate by 26%.  This could be due in part to upregulation of lipoprotein lipase (LPL) gene expression and activity in the skeletal muscle during the recovery period following resistance training.
As we’ve already stated, aging and loss of muscle limit your ability to handle glucose via a reduction in GLUT4 translocation. 
However, resistance training involves powerful muscle contractions, mediating GLUT4 translocation to the muscle membrane independent of insulin. This occurs through calcium/calmodulin-dependent protein kinase IV as well as AMPK. As a result, PGC-1α activity increases.
Why is this important?
PGC-1α is a transcriptional coactivator required for mitochondrial biogenesis.
This becomes all the more noteworthy when you consider that mitochondrial function can be reduced by 40% with aging and type 2 diabetes, further contributing to impaired glucose uptake and the development of insulin resistance. [24,25]
Remember, mitochondria are the mini “nuclear reactors” inside each cell the provide energy to keep the cell running. Mitochondria create this energy from a mix of glucose and fatty acids. Impaired mitochondrial function (i.e. impaired energy production) or a reduction in the number of mitochondria both limit your ability to efficiently metabolize glucose and/or fatty acids.
Now, if you remember back to high school biology, glucose, upon entering the cell, can be oxidized immediately for energy or converted to glycogen (the storage form of glucose). Type 2 diabetes have been documented to have worse glycogen synthesis rates compared to healthy subjects. 
Enter resistance training, which can help counteract the metabolic dysfunction brought on by aging and type 2 diabetes. Not only does resistance training stimulate glucose uptake into skeletal muscle independent of insulin, but it also helps retain and increase lean muscle mass.
Additional studies indicate that training programs that include resistance training may be particularly useful for type 2 diabetes due to improvement in insulin sensitivity. The reason for this is that greater muscle mass is associated with better glycemic control as skeletal muscle is the largest insulin-sensitive tissue in the body. [11,12,13]
Essentially, skeletal muscle serves as a giant “sink” for glucose in the body. The more muscle you have, and the more frequently you stress it with tension overload (i.e. lifting heavy weights), the more glucose your body can handle and the better it can handle it.
Put another way, lifting weights helps increase muscle mass and strength, giving you better control over glucose while combating insulin resistance.
Remember, repeated muscle contractions upregulate AMPK activity, deactivating protein TCB1D1, which enhances GLUT4 translocation, ultimately increasing glucose uptake into skeletal muscle. 
Moreover, exercise also improves insulin sensitivity via increasing capillarisation in skeletal muscle.  This increases the network of blood vessels in the body providing a separate (and independent) adaptation that boosts insulin sensitivity.
And finally, high-intensity exercise also increases β cell activity. β cells are the cells in the pancreas that secrete insulin. 
Finally, researchers have identified one of the exact mechanisms through which resistance training enhances insulin sensitivity -- it enhances the effects APPL1 (Adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1) -- a protein that regulates blood sugar absorption in the body. 
Simply put, there’s no logical reason to avoid resistance training. It can and should be included in the physical activity recommendations doctors give their diabetic patients.
It helps increase lean muscle mass, improves insulin sensitivity, lowers HbA1c, reduces insulin, enhances glycemic control, and reduces fat mass. Aerobic training does little to build muscle and there’s even some research to show aerobic training is inferior to resistance training for improving the diabetic markers outlined previously.
All that being said, aerobic training can still be a part of your exercise regimen, and it should be as aerobic exercise can improve endothelial vasodilator function, which may enhance blood flow and glucose uptake in muscle tissue.
This is why the solution to exercise programs for diabetics should be BOTH aerobic and resistance training as it helps combat symptoms of the disease through different mechanisms. [30,31]
So, which is better -- resistance training or aerobic training for the prevention and treatment of type 2 diabetes?
That’s not the question you should be asking.
Both have been shown in research to be effective for improving insulin sensitivity and glucose tolerance.
Therefore, you can and should be performing both types of exercise each week, especially when you consider the fact that some research indicates that exercise regimens including both aerobic and resistance training may be more efficacious for treating symptoms of type 2 diabetes than either exercise mode alone. 
Doctors and patients both need to be aware of the most effective treatments for treating type 2 diabetes. Based on the latest evidence, the “most effective” treatments MUST include resistance-training.
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