As the earth tilts away from the sun on its axis, the days shorten and temperatures drop. The leaves fall. Growing things disappear beneath snow and ice. Water freezes over. Life seems to come to a standstill. We call this season winter.
As the days shorten and temperatures drop, food becomes scarce. Polar bears prepare to den. Whenever a warm-blooded animal is exposed to cold, it triggers a cascade of biophysical effects. Cold immediately activates brown fat, which sits over the spinal cord and burns fat to generate heat. Brown fat allows warm-blooded animals to survive ice ages and Arctic winters. As temperatures continue to drop, brown fat grows in size and power. Brown fat is what burns the 50% of a polar bear’s body weight that it loses during winter hibernation.
The light of summer slowly fades into the darkness of winter. Light is the signal for wakefulness, and as this signal wanes, sleep nears. Only in the absence of light can the hormone of sleep that we call “melatonin” be released to regenerate the body. Melatonin is produced all over the body, but it is released from the pineal gland at night after three to four hours of darkness. When blue and green light strike the back of the eye (the retina) or the skin, they send an electrical signal to the brain that suppresses melatonin release. The constant light of the Arctic summer leads to chronically low melatonin levels, and, coincidentally, a lack of sleep. Melatonin is not only the hormone of sleep, but the hormone of regeneration, which only happens during sleep. When life lacks melatonin, life falls apart. This is why polar bears gain weight and become slightly diabetic. Melatonin is what keeps the mammalian metabolism healthy.
Melatonin determines metabolism, not only by maintaining cellular metabolism, but by controlling hormones and neurotransmitters. Modern humans are beset by epidemics of disease that are linked to hormones and neurotransmitters. The most important environmental signal for the synthesis and release of hormones and neurotransmitters is light. Melatonin is the lever that light uses to entrain the rhythms of our hormones and neurotransmitters. Today, we are seeing record levels of low testosterone, low progesterone, low thyroid hormone, low serotonin, and low catecholamines (better known as dopamine, epinephrine, and norepinephrine). What else would we expect in a world of fake light, where we chronically deprive ourselves of melatonin?
As darkness descends upon the Arctic and temperatures drop, the polar bear’s brown fat turns into the furnace that will sustain it through the bitter cold of winter. Melatonin drives this process and repairs the polar bear’s metabolism, so that it can burn fat cleanly and efficiently.
The polar bear goes to sleep for months and emerges in the Spring having reversed diseases that today require heroic efforts of diet and exercise, or even bariatric surgery. The polar bear needs none of these contrivances.
The antidote to an endless summer is a long, cold winter. The answer to our modern epidemics is here.
Modern medicine already knows this, and Polar Bear Fitness is meant to bring it to your doorstep.