Late Winter Fatigue Isn’t Laziness. It’s Physiology.
a quiet recalibration of light, hormones, and energy as the season shifts.
By the UWM editors
By late February, many people report feeling more fatigued than they did in December. Motivation drops. Workouts feel harder. Sleep can feel less restorative. But this pattern has more to do with seasonal biology than with a lack of discipline or motivation.
Light, Cortisol, and Seasonal Energy
Human circadian rhythms are regulated by light exposure. Reduced daylight during winter alters signaling from the suprachiasmatic nucleus in the brain, which influences cortisol release and sleep timing. Studies have shown that light exposure directly affects the hypothalamic-pituitary-adrenal (HPA) axis and cortisol rhythms.
In contrast, prolonged low-light exposure can flatten normal cortisol variation, contributing to fatigue and mood changes. Longer stretches of daylight may be a positive thing, but as daylight lengthens, the body must recalibrate hormonal timing, which temporarily increases metabolic demand.
Brain Energy Demand Remains High
The brain accounts for roughly 20 percent of total energy consumption despite representing only about 2 percent of body weight. Even when physical activity decreases in winter, cognitive demand does not.
Seasonal shifts in serotonin and dopamine regulation have been observed in response to changes in light exposure. These neurotransmitter fluctuations may contribute to reduced motivation and increased mental fatigue during late winter. As is often the case, it’s the time of transitions that can cause an increase in our mental and physical workload.
Immune and Histamine Shifts
As temperatures fluctuate and early plant cycles begin, histamine activity can increase. Histamine is involved not only in allergic responses but also in inflammation and wakefulness. Rising histamine load may contribute to fatigue, sinus pressure, or headaches in sensitive individuals.
Barometric pressure changes have also been associated with shifts in inflammatory symptoms. The immune system is adjusting to environmental change, and that adaptation requires energy.
Circadian Realignment
Even modest changes in photoperiod can alter melatonin secretion timing and sleep architecture. During seasonal transition, sleep may feel lighter or less restorative until rhythms stabilize.
In other words, the body is recalibrating multiple systems at once: hormonal timing, immune vigilance, neurotransmitter regulation, and sleep architecture.
Supporting the Transition
Late winter is not the time for aggressive resets. Instead, support foundational systems:
Morning outdoor light exposure
Consistent meal timing with adequate protein
Moderate strength training to support mitochondrial function
Mineral sufficiency and hydration
Reduced evening light exposure
Creatine and Cellular Energy
Creatine plays a key role in regenerating ATP through the phosphocreatine system. Research suggests creatine supplementation may improve cognitive performance under sleep deprivation and may support brain energy metabolism.
Creatine is not a stimulant. It supports rapid energy buffering at the cellular level in both muscle and brain tissue. In seasons where energy demand shifts, supporting ATP availability may be more physiologically aligned than increasing caffeine intake.
Closing Reflection
The human body is not built for constant peak output. It responds to light, temperature, and environmental signals whether we notice them or not.
Late winter fatigue often reflects adaptation rather than decline. When systems recalibrate, energy may dip before it rises. Supporting the transition allows motivation to return on its own timetable.