The role of insulin in the body

Diabulimia is a sad condition where diabetics skip taking their insulin in the fear that it’s making them fat. Blood sugars go up, and if you’re unlucky, you can end up with diabetic ketoacidosis and die. It helps to know a little bit about insulin as a type 1 diabetic, as you’re going to spend the rest of your life injecting it.

Insulin is an anabolic hormone, which means it tells the body that energy is abundant and that you should switch to storage mode. Together with glucagon, it regulates energy metabolism. Insulin does many things in the body, which is why we need it to live. The effect of insulin is most prominent in the liver, fat, and muscle tissues. Let’s look at some of these important functions.

Carbohydrate metabolism

In the liver, insulin decreases the production of glucose. The process is ongoing, as the liver is continuously pushing glucose into the blood to give energy to the cells. We take basal insulin for this reason. Glycogen (stored glucose) goes from being used to produced in both the liver and the muscle tissue. Fat and muscle cells increase their uptake of glucose to lower the concentration in the blood. Note that glucose can still enter cells in the absence of insulin, just at a much lower rate, which causes the toxic build-up in diabetic ketoacidosis.

Fat metabolism

Insulin makes fat cells stop releasing fatty acids by inhibiting the activity of hormone-sensitive lipase. It also increases the formation of triacylglycerol which binds to fatty acids and forms the backbone of our stored fat. 

Protein metabolism

While insulin has a smaller role, it stimulates the entry of amino acids into cells and drives the synthesis of many proteins that we need for cellular housekeeping.

It potentially does other things that we haven’t discovered yet, as is often the case in biochemistry. You shouldn’t be scared of injecting it, especially not because you think it will make you fat. This is only a problem in insulin resistance (such as metabolic syndrome and type 2 diabetes), where high levels of circulating insulin keep the body in storage mode and prevent it from burning fat. If your insulin requirements are “normal” (0.5-1u of insulin/ kg of body weight/ day) it shouldn’t be a problem to lose weight and still take your insulin.

Be aware that just like anyone else you can become insulin resistant (>1u of insulin/ kg of body weight/ day) as a type 1 diabetic if you eat a lot of carbohydrates. Type 1 diabetes unfortunately doesn’t stop you from developing type 2 in what is called double diabetes. The best way to deal with insulin resistance that I’ve come across on my readings seems to be intermittent fasting.

Source for metabolic biochemistry: Harvey, Richard, & Pamela, Champe (2005) Lippincott’s biochemistry, Metabolic effects of insulin and glucagon, 3rd edition, Lippincott Williams & Williams