When we think of hibernation, certain animals come to mind – but not always humans. We also are part of this natural cycle, and it affects our metabolism.

Like other animals, the human body naturally changes to create an insulin-resistant state. This helps our system be more fuel-efficient and go for long periods of time with a smaller amount of food.

This is a naturally occurring seasonal event in all vertebrates. This survival mechanism has been preserved for almost 400 million years of evolution and is essential to regulate metabolism.

Storing fat

During the seasonal change, which occurs around late summer/early fall, our brain tells our body to increase its insulin resistance. As a result, our liver can increase fat production, and our adipose and non-adipose tissues can store fat to get ready for winter. Ants get ready for winter by putting away their winter food; we get ready by storing fat in our body.

We now understand better that our central nervous system is in command and control of our peripheral fuel metabolism functions, such as liver glucose and lipid metabolism, adipose metabolism, muscle physiology, pancreatic insulin and glucagon secretion, as well as cardiovascular biology.

The liver also is asked to increase glucose production to be able to send blood glucose to the brain, which needs it the most. Our brain also controls the peripheral tissues that can decrease glucose use and increase fat instead.

Switching to hibernation mode

The brain’s command-and-control center is located deep in the spot between our eyebrows, near the hypothalamus. Orders are transmitted via the neuroendocrine axis with different signaling pathways that switch our system to hibernation or vice versa. This low brain area, which controls the hypothalamic dopamine activity, is the key player for the insulin-resistance state in humans.

Interestingly, a low level of dopamine activity also has been found to be associated with obesity and Type 2 diabetes.

For some of us, this annual cycle of insulin resistance reverses back to an insulin-sensitive state around late winter/early spring to get ready for summer and an abundance of food.

For others, the circadian dopamine input to the brain, particularly the biological pacemaker called SCN, is lost. When that happens, we lose the key regulator of this annual cycle of peripheral glucose and lipid metabolism and remain in our hibernation mode summer and winter, all year round.

Seeing the cycles

If you have diabetes and use insulin as your main therapy, you might have noticed these cyclical changes. For instance, have you ever noticed that your blood sugar levels suddenly are higher in early fall?

Or in early spring, have you noticed that you start having more hypoglycemia despite using the same insulin amount, physical activity and food? This could be related to your metabolic cycle.

The scientific community continues to study metabolism to understand it better and develop ways to help diabetic patients reverse insulin resistance. More research is needed to further advance the field.

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