Muscle Building & Insulin Sensitivity: Understanding the Connection


By Colette Nelson

Are some of the things we do to build muscle actually making us predisposed to type 2 diabetes?

Let’s start with the differences between type 1 and type 2 diabetes. Type 1 diabetes is an autoimmune disease that usually occurs in children; however, we no longer call it “juvenile diabetes,” as we now understand that it can happen at any stage in a person’s life. Indeed, it is the fastest-growing autoimmune disease in the world. People who have type 1 diabetes will need to take insulin for the rest of their lives. Without it, they will go into diabetic ketoacidosis and eventually die if they are not given fluids and insulin. (This is not to be confused with ketosis, a metabolic state in which most of the body’s energy supply comes from ketone bodies in the blood.)

Type 2 diabetes, which we used to call “adult-onset diabetes,” is often referred to as a disease of lifestyle, but it is so complex that it’s hard to determine what causes it. Risk factors include being over 45, being overweight, having a family history of it, and being sedentary. People who belong to certain racial or ethnic groups are also predisposed to type 2 diabetes, including African-Americans, Hispanics, Asians, Pacific Islanders and American Indians.

We often think of type 2 diabetics as being overweight and sedentary. In addition, the condition is often accompanied by hypertension (high blood pressure), hypercholesterolemia (high cholesterol), and hyperglycemia (high blood sugar), which contribute to glucose intolerance in a number of ways. Those characteristics do not fit the typical male or female bodybuilder or fitness enthusiast who finds that his or her fasting blood sugar is over 100 mg/dl.

The Effect of Carbs

The beta cells are the insulin-producing cells located in the pancreas. Your beta cells have to make insulin 24 hours a day—even when you don’t eat. Imagine if you feed your body tons of carbs, which forces the pancreas to work harder. That can’t possibly be good, right? What happens with those who are sedentary rather than athletic? Exercise works like an invisible insulin shot, as the muscle cells are among the only cells in the body that can uptake glucose without insulin.

Unless you are an endurance athlete, however, excess carbs can be toxic to the body, as they all convert to glucose—and diseases like cancer love excess glucose. In people who don’t exercise, all those carbs have nowhere to go and are stored as fat. Since insulin holds water, and fat creates insulin resistance, you start to experience high blood pressure, high blood fats, and, eventually, high blood sugar and metabolic syndrome, which is also known as syndrome X.

The Role of Insulin

Traditionally, type 2 diabetes was characterized as non-insulin-dependent diabetes, but in the year 2000, Sanofi became the first pharmaceutical company to create a 24-hour long-acting insulin, known as Lantus (insulin glargine). That advancement changed the scope of treatment for type 2 diabetes. We had started to recognize that it was a progressive disease, with the beta cells losing about 5 percent of their function each year. If you do the math, you can see that someone who lives with type 2 diabetes for more than 20 years will likely produce very little insulin and will need treatment with exogenous, or DNA recombinant, insulin. So it is clear that insulin is no longer just for treating type 1 diabetes.

We now also recognize the importance of blood glucose control. Glycosylation of the red blood cell starts at a blood sugar over 120 mg/dl, and starting treatment with long-acting insulin—a basal bolus—earlier in the disease progression can function as beta cell recovery and halt the progression of the disease. So you can see where giving patients insulin earlier would help them avoid burning out the beta cells to where they would need multiple daily injections of insulin or an insulin pump delivery system to control their blood sugar. Insulin should no longer be demonized by doctors and used as a threat to patients who are struggling to get their blood sugar under control.

The Muscle-Building Connection

What about you, however? How could a bodybuilding lifestyle possibly contribute to your getting type 2 diabetes? Let’s start with your diet. In their desperation to grow and put on muscle, many people believe they need more calories, and carbs often become a key fuel source in bulking diets. I have heard of bodybuilders taking in more than 1,000 grams a day of carbs. Imagine the stress on their beta cells! Let’s face it—working out with weights one to two hours a day does not require 1,000 grams of carbs. Your beta cells will have to work very hard to maintain glucose homeostasis. I often question the cost-to-benefit factor of using preworkout, intraworkout, and/or postworkout sugar loads that supplement companies claim are the key to your growth and success in the gym.

What happens when you add some insulin-resistant hormones and drugs to the equation? If that’s something you’re considering—or doing—here are some points you may want to think about.

To begin with, growth hormone, or GH, raises your blood glucose. It is what we call an anti-insulin hormone because it raises blood glucose while insulin lowers it. In fact, some physicians induce low blood sugar to test growth hormone response. Let’s say you start doing GH dosages of 6 to 18 IU a day. Imagine how the glucose resistance adds fuel to the fire in your insulin-producing beta cells. Now your beta cells have to deal with 1,000 grams of carbs and 10 units of growth hormone. To say that they’re working overtime would be an understatement!

But wait. As if that isn’t enough, add some clenbuterol or amphetamines—they all increase blood sugar due to the flight-or-fight response. Ask any type 1 diabetics how their blood sugar responds to clenbuterol or even coffee. That makes three glucose-resistant markers the beta cells are dealing with that potentially can cause the cells to burn out.

What about pain? Let’s say you get a cortisol shot. Now you’ve introduced the most insulin-resistant hormone into your body. Whether it’s cortisone shots or prednisone, I have seen patients with chronic asthma develop type 2 diabetes with long-term corticosteroid use.

Note that anabolic steroids such as testosterone have the opposite effect and actually help with insulin sensitivity. So that is a positive note in terms of what might be contributing to glucose intolerance in a bodybuilder. It isn’t the anabolics but the other drugs mentioned above.

Diuretics are not to be taken without caution—and not just from the standpoint of electrolyte imbalances. Read the package insert of any diuretic, and you will see hyperglycemia as one of the possible adverse effects. When the body cells are dehydrated, insulin has a difficult time moving into the cells. I know bodybuilders who cheat on their diets and take diuretics regularly, which aggravates their glucose intolerance.

 Are you starting to see where I am going?

In addition, many bodybuilders take antidepressants. This class of drug has a negative impact on cellular uptake of glucose, increasing insulin resistance. So once again the beta cells need to push out more insulin to maintain normal blood sugar.

I have worked with many big names in the sport who are essentially type 2 diabetics, not from the common risk factors mentioned earlier in this article but because of lifestyle choices made in their effort to get big and maintain a certain size. There are some new and interesting approaches you can take to ensure that your beta cells stay healthy while you’re trying to put on muscle. Stay tuned for more about that in the next installment of The Diabetes Blog.

Got a question for Colette? In future posts Colette Nelson will answer readers’ questions on diabetes, glucose control, insulin sensitivity and the muscle-building connection, and related topics. Send your questions to

Also See: Millions Don’t Even Know They Have Diabetes!

Colette Nelson has spent years showcasing her talents in the fitness arena, but her passion for teaching people about diabetes is what brings her to A registered dietitian and certified diabetes instructor, she holds an M.S. in clinical nutrition from NYU and is a consultant to various equipment and pharmaceutical companies. An IFBB pro bodybuilder and former World Amateur champion, Colette is known for her artistry in the posing round (she also studied dance) and she has choreographed the routines of numerous top competitors. She’s an AFFA- and ACE-certified personal trainer and aerobics instructor and provides contest-preparation services in the areas of diet, training, makeup, tanning, and posing. She created Team Colette in 2013 as a safe place for her clients to share their weight-loss experiences and motivate each other to stay focused on their goals.