How Winter Hormones Affect Mood, Sleep, and Energy
Winter changes more than the weather. Shorter daylight, colder temperatures, and altered routines can shift key hormones and neurotransmitters that influence mood, sleep, appetite, metabolism, and energy. Many people notice “winter blues,” stronger carb cravings, lighter sleep, or a dip in motivation. These patterns often trace back to circadian rhythm changes that affect signals like melatonin, serotonin, thyroid hormones, cortisol, leptin, and ghrelin, along with vitamin D status and brown fat activity.
This guide explains what the research suggests about winter’s hormonal effects, what is well established versus still emerging, and how to respond in practical, safe ways. You will find plain-language explanations, clinician-informed tips, and sensible steps you can discuss with your healthcare provider, including light timing, sleep hygiene, movement, and nutrition that support healthy hormone balance through the colder months.
How light in winter shifts melatonin, serotonin, and mood (SAD)
How shorter days affect your body clock
Light is the strongest signal for your circadian rhythm. In winter, later sunrises and earlier sunsets can push your internal clock later, raising nighttime melatonin for longer and reducing daytime alertness. Many people feel sleepier, less motivated, or “out of sync” as a result.
Why mood can dip
Lower daylight exposure also links to lower brain serotonin activity, a neurotransmitter tied to mood, appetite, and sleep quality. This partly explains seasonal affective disorder (SAD) and milder “winter blues,” especially when routines drift and outdoor time shrinks.
Practical steps that help
Aim for 20–30 minutes of outdoor morning light within an hour of waking, even on cloudy days. Keep a consistent wake time, get light on your eyes (no sunglasses initially), and move your body during that window to amplify the effect. For recurrent winter depression, discuss bright light therapy and other treatments with your clinician.
Safety notes
If mood symptoms persist, include thoughts of self-harm, or significantly impair daily life, seek care promptly. Light boxes should be used as directed to avoid eyestrain, headaches, or circadian disruption.
Does winter change thyroid hormones?
What studies suggest
Research shows thyroid-stimulating hormone (TSH) often runs a bit higher in winter, and free T3 can trend higher as the body adapts to cold. These changes may be modest and vary by climate, but they can overlap with symptoms people notice in colder months.
How this feels day to day
Common winter complaints include low energy, feeling cold, dry skin, and “brain fog.” These can reflect circadian changes, nutrition, illness, or true thyroid dysfunction. Seasonal TSH shifts alone don’t confirm hypothyroidism.
When to test and how to interpret
If symptoms persist for weeks, discuss labs with your provider. A proper panel often includes TSH and free thyroid hormones, interpreted alongside history, medications, and iodine/selenium status. Avoid starting or changing thyroid medication without medical guidance.
Actionable supports
Prioritize regular sleep, protein-rich meals, and micronutrients that support thyroid function from food sources (selenium in Brazil nuts/seafood, iodine in seaweed/iodized salt, iron from legumes/lean meats, zinc from seeds and shellfish). Re-check labs only as clinically indicated.
Appetite hormones in cold weather
Cold exposure and shorter daylight can tilt appetite signals. Ghrelin, which stimulates hunger, may rise with cold and irregular sleep. Leptin, which supports satiety, can be less effective when sleep and activity patterns change, making carb-rich foods more tempting.
What this looks like day to day
People often report stronger cravings for bread, pasta, and sweets, larger portions, and more evening snacking. The combination of extra calories plus less movement can gradually increase weight over the season.
Practical nutrition moves
Anchor meals with protein and fiber at breakfast and lunch to improve satiety.
Add warm, high-volume foods like soups, stews, beans, and vegetables.
Pair carbohydrates with protein or healthy fats to slow digestion.
Keep a consistent eating window and regular sleep to steady hunger cues.
When to check in with a clinician
If appetite changes come with rapid weight gain, persistent low mood, or suspected binge patterns, discuss individualized support and screening for thyroid, iron, vitamin D, and glucose regulation.
Vitamin D, immunity, and energy through winter
Why levels drop
With less UVB exposure, many people see vitamin D decline in late fall and winter. Low vitamin D is linked to low mood, increased fatigue, and suboptimal immune function.
Testing and targets
Consider a 25-hydroxyvitamin D blood test if you have winter fatigue, frequent infections, limited sun, darker skin pigmentation, or cover most skin outdoors. Discuss an evidence-based target range with your clinician and recheck only as advised.
Food vs supplements
Fatty fish, egg yolks, fortified dairy or plant milks contribute vitamin D, but diet alone is often insufficient in winter. Supplementation can be appropriate at clinician-guided doses, taken with a meal that contains fat to aid absorption.
Safety notes
Avoid high-dose self-supplementation without labs and guidance. Very high intakes can raise calcium and cause adverse effects.
Cortisol in winter: stress, sleep, and recovery
What the research suggests
Some studies report higher cortisol levels in winter, while others show little or no seasonal change. Practical takeaway: assume individual variability and focus on behaviors that stabilize your stress system rather than chasing a single “winter cortisol” pattern.
How this shows up day to day
People may notice afternoon slumps, lighter sleep, or higher evening alertness if routines drift later. Irregular light exposure, more screen time at night, and less outdoor activity can all nudge your circadian rhythm and stress response.
What you can do
Keep a consistent wake time and get morning outdoor light.
Train earlier in the day when possible and finish vigorous exercise at least 3 hours before bed.
Use brief daytime relaxation practices such as slow breathing, a short walk, or a 10-minute body scan.
Set a nightly “wind-down” window with dimmer lights, quieter tasks, and no caffeine after mid-afternoon.
When to check in
If stress, anxiety, or insomnia persist for weeks or impair work and relationships, speak with a clinician. Consider screening for mood disorders, sleep apnea, thyroid issues, iron deficiency, and glucose regulation as appropriate.
Brown fat and cold adaptation: what it means for metabolism
Brown adipose tissue in a nutshell
Brown fat helps generate heat by burning calories through non-shivering thermogenesis. Cold exposure can activate brown fat, which may support metabolic flexibility. The magnitude of effect varies by age, body composition, sex, and genetics.
Practical expectations
Cold exposure is not a stand-alone weight loss tool. It may complement movement, nutrition, and sleep by improving tolerance to cold and potentially aiding energy balance at the margins.
Ways to stimulate safely
Spend more time outdoors in cool temperatures with appropriate clothing.
Finish showers with 30–60 seconds of cool water if comfortable.
Layer activity with cool air, such as brisk walks in a light jacket.
Focus first on consistency and comfort rather than extremes.
Safety notes
Avoid cold exposure if you have cardiovascular disease, uncontrolled hypertension, Raynaud’s phenomenon, neuropathy, or if you are pregnant, unless cleared by your clinician. Stop immediately for chest pain, dizziness, or numbness beyond normal chill.
Sleep strategies that realign your winter body clock
Why winter shifts sleep
Shorter days and later sunrises can push your circadian rhythm later, which makes you sleepy in the morning and more alert at night. Indoor evenings with bright screens reinforce the delay, so you fall asleep later but still wake early for work, creating sleep debt.
Build a steady daily anchor
Keep the same wake time every day, including weekends. Treat wake time as non-negotiable and allow sunlight, movement, and a protein-forward breakfast to “stamp” that time in your biology. Most people notice better energy within one to two weeks of consistency.
Front-load daylight, especially in the morning
Get outside within an hour of waking for 15–30 minutes. Even on overcast days, outdoor light is far stronger than indoor lighting and helps suppress residual melatonin so you feel alert earlier. If you have recurrent winter depression, ask a clinician about clinically tested bright-light devices and timing.
Create an evening wind-down
Aim for a 30–60 minute buffer before bed: dim lights, quiet tasks, light stretching, or reading. Reduce large late-night meals and limit screens or use blue-light reduction if you must be on devices. Finish vigorous workouts at least three hours before bedtime.
Caffeine, alcohol, and naps
Stop caffeine 8–10 hours before bed. Alcohol fragments sleep and can worsen early-morning awakenings; if used, keep it light and earlier. Naps should be short (10–20 minutes) and before late afternoon to avoid delaying bedtime.
When to seek help for sleep
If you snore loudly, gasp at night, or wake unrefreshed despite 7–9 hours in bed, ask about sleep apnea or other sleep disorders. Persistent insomnia, restless legs, or circadian rhythm problems benefit from medical evaluation and structured therapies.
When symptoms signal a medical condition vs seasonal change
Red flags that warrant prompt care
Seek evaluation for suicidal thoughts, severe or persistent depression, unintentional weight loss or gain, chest pain, fainting, new severe headaches, or neurological changes. These are not typical “winter blues” and require medical attention.
Thyroid and nutrient considerations
Winter fatigue and feeling cold can be seasonal, but prolonged symptoms may reflect thyroid dysfunction or nutrient issues. Discuss testing for TSH and free thyroid hormones when appropriate, and consider iron studies, B12, and vitamin D based on history and risk.
Mood and energy beyond seasonal patterns
If low mood lasts most days for more than two weeks, includes loss of interest, guilt, sleep or appetite changes, or thoughts of self-harm, seek care. Seasonal affective disorder responds to structured treatments that your clinician can tailor to you.
Metabolic and cardiometabolic signs
Increased thirst, frequent urination, or blurry vision warrant glucose screening. New or worsening blood pressure, chest discomfort with exertion, or reduced exercise tolerance should be evaluated, especially in colder weather when cardiovascular strain can rise.
Infections and immune health
Frequent or severe infections, prolonged cough, or fevers need clinical review. Winter is a high-incidence season for respiratory illnesses, and early assessment supports recovery and reduces complications.
Movement and training plans that work in cold weather
Why movement matters in winter
Regular activity stabilizes circadian rhythm, supports serotonin and dopamine, improves insulin sensitivity, and helps manage appetite signals like leptin and ghrelin. Even modest, consistent movement reduces winter fatigue and improves mood.
Build a weekly base
Aim for most days of the week with 20–40 minutes of moderate effort. Brisk walking, indoor cycling, rowing, or bodyweight circuits all count. If you train outdoors, warm up indoors first and layer clothing to protect joints and airways.
Use simple structures
Try 2–3 strength sessions and 2–3 aerobic sessions per week. For strength, focus on compound movements such as squats, hinges, pushes, and pulls. For aerobic work, maintain a conversational pace on most days and add brief intervals only if well rested.
Recovery that protects sleep
Finish vigorous workouts at least three hours before bedtime. Include a short cooldown and light stretch to lower arousal. Keep hydration, protein intake, and consistent meal timing to support recovery and stable energy.
Takeaway
Winter affects hormones through changes in light, temperature, and routine, influencing mood, sleep, appetite, and energy. Consistent morning light, regular movement, balanced nutrition, and timely testing create a safe, evidence-informed plan. If symptoms persist or disrupt daily life, book an appointment with a healthcare provider for personalized evaluation and treatment.
References
Yoneshiro, T., Matsushita, M., Sakai, J., & Saito, M. (2025). Brown fat thermogenesis and cold adaptation in humans. Journal of physiological anthropology, 44(1), 11. https://doi.org/10.1186/s40101-025-00391-w
Cahill, S., Tuplin, E., & Holahan, M. R. (2013). Circannual changes in stress and feeding hormones and their effect on food-seeking behaviors. Frontiers in neuroscience, 7, 140. https://doi.org/10.3389/fnins.2013.00140
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