Metabolic Adaptation: Seasonal Shifts from Summer Burn to Winter Storage

Key Takeaways

• Seasonal metabolic changes cause your body to shift from higher summer “burn” to winter “storage,” driven by less sunlight, colder temperatures, and activity levels.
• Hormonal shifts in melatonin, cortisol, leptin, and ghrelin during winter can impact sleep, appetite, and energy levels, influencing overall metabolic adaptation.
• Build year-round metabolic resilience by focusing on balanced nutrition, movement, sleep, and stress management with a CGM, and understand your metabolism through every season. 

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Seasonal changes impact all living things. For example, the beautiful fall leaf colors result from reduced sunlight, which triggers the veins that feed the leaves to seal off. This stops nutrient flow, causing the color change and the eventual fall of all the leaves. Trees can survive the winter by storing the extra nutrients, conserving energy, and slowing their metabolism.¹

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Humans also adapt metabolically to seasonal changes stemming from less sunlight and cooler temperatures, which can lead to dietary and seasonal metabolic changes.²

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In this article, learn about the shift from “burn” mode in the summer to “store” mode in winter, and how to adapt with science-backed strategies and strive for metabolic resiliency year-round. 

The Science of Seasonal Metabolism

Seasonal metabolism refers to the minor shift that occurs as daylight hours shorten. On the shortest day of the year, December 21, the Midwest may experience 9 hours of daylight, southern states will have 10 hours of sunlight, and northern regions as few as 8 hours. In the summer, daylight can increase by 5 or 6 hours.³ 

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Reduced daylight hours affect your circadian rhythm (your internal clock), leading to changes in melatonin, cortisol, leptin, and ghrelin levels that can slightly influence your metabolism. 

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Here’s a breakdown of each hormonal change and its effect on the body:

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• Melatonin: During winter, melatonin levels remain elevated longer than in summer. Melatonin encourages sleep and feelings of tiredness. You may not necessarily sleep more in the winter, but your energy levels often dip compared to summer.⁴
• Cortisol: A 2021 study of 6.3 million laboratory records over 15 years found clear seasonal patterns (a 5% shift) in stress hormones, thyroid function, reproduction, and growth. Cortisol (a stress hormone) was higher in the winter and early spring, possibly due to colder temperatures and reduced sunlight.⁵ 

Elevated cortisol plus circadian rhythm changes can contribute to mood changes, sometimes leading to seasonal affective disorder (SAD), which includes symptoms such as daytime sleepiness, overeating, carbohydrate cravings, fatigue, less physical activity, and a depressed mood.¹

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• Leptin: Hotter temperatures raise leptin levels, the hormone that makes you feel full and stop eating. In colder temperatures, leptin levels drop, potentially increasing hunger and appetite.⁶
• Ghrelin: Known as the “hunger hormone,” ghrelin stimulates appetite and fat storage. Research indicates that cold weather can increase ghrelin, potentially boosting appetite during the winter months.⁶ 

While most research indicates that these are minor effects, you may notice subtle changes in appetite and energy levels that are likely related to seasonal changes. 

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Knowing this information can help you give yourself grace and make minor behavioral changes to strive for metabolic health year-round. Being indoors more, with a slightly increased appetite and less energy for exercise, could lead you to eat more in the winter. 

Summer Burn vs. Winter Storage

Summer embodies more energy “burn.” With 5 to 6 extra hours of daylight, warmer temperatures, and longer days, we naturally expend more energy.

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Research consistently shows that people of all ages are more physically active in summer. In one study of 127 older adults, participants were twice as active in the summer as in the winter, driven by longer days, more sunshine, and warmer temperatures.⁷

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Studies are mixed on whether resting energy expenditure is altered in the winter. Some studies show that resting metabolism is slightly higher (5-14%) in winter to help people stay warm, and the effect is more pronounced in younger, leaner people.⁸

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On the other hand, physical activity drops significantly in winter, so total energy burn is lower. Numerous studies report reduced physical activity and intensity in the winter months. One study found that 57 women in Nashville, Tennessee, spent 35 more minutes per day in sedentary activities during the winter than in the summer.⁹

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A 2021 systematic review including 1,951 adults reported evidence of seasonal variation: 

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• Sleep was longest in the fall (+12 minutes)
• Sedentary activities peaked in the winter (+19 minutes)
• Physical activity was highest in the summer (+19 minutes) compared to yearly averages.¹⁰ 

In winter, reduced activity, more time spent indoors, and a slight increase in appetite can lead to weight gain (or winter storage). Some researchers hypothesize that the body tends to store energy in winter conditions to prepare for survival in colder weather.¹¹ 

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Modern life amplifies this: the winter season brings holiday meals, social gatherings, and comfort foods, increasing calorie intake. Combined with hormonal changes from less sunlight and colder temperatures that increase appetite, it creates a perfect set-up for “storage mode.”¹¹ 

The Metabolic Playbook: Countering Winter Storage Mode

When the days get shorter and the temperature drops, your body naturally shifts into “winter mode.” Evolutionarily, this meant conserving energy and storing fat to survive colder months. Today, it just means it’s a little easier to reach for comfort food and a little harder to stay active. But with the right tactics (and data from Signos), you can outsmart that biological instinct and stay in metabolic balance all season long.

Nutrition

Focus on foods that keep your energy steady and your hunger in check. Prioritize protein and fiber, and lean into seasonal produce like carrots, potatoes, onions, kale, Brussels sprouts, and broccoli. Fermented foods (yogurt, kefir, sauerkraut, kimchi, kombucha, and pickles) can also support gut health, which, in turn, impacts glucose control.

Movement

Cold weather can actually work to your advantage. Exercising in cooler temps and adding a bit of cold exposure can increase brown fat activity, which helps your body burn energy more efficiently. Aim for low to moderate-intensity cardio (Zone 2 training) and strength work to keep your metabolism strong.

Sleep

Shorter days can mess with your body clock, so keep your circadian rhythm steady by sticking to a consistent sleep schedule. Try to get some natural light exposure within the first hour of waking; it’s one of the simplest ways to support better sleep and glucose stability.

Stress

Cortisol, your stress hormone, can spike glucose levels when left unchecked. Use winter as a time to double down on stress management: try breathwork, walks in nature, connecting with friends, or setting firm boundaries around rest. Quality sleep will also help keep cortisol in check.

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Experiments to Try with Signos

Winter is the perfect time to experiment and see how your metabolism responds to these shifts. A few ideas to get started:

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• Compare your cold-weather glucose curves: Check how your glucose patterns differ between warm and cool days. Does your body react differently after a chilly morning walk vs. a cozy indoor one?
• Run a “comfort food” experiment: Try your favorite winter meal twice—once with added protein and fiber, and once without, and see how it affects your post-meal glucose.
• Track stress and sleep impact: Notice if nights of shorter sleep or high stress correlate with higher morning glucose or more cravings.
• Experiment with timing: Test how eating dinner earlier vs. later impacts your overnight stability.

Using Signos to Track Seasonal Metabolic Shifts

Signos helps you visualize how your metabolism adapts through seasonal changes, so you can make smarter adjustments instead of guessing.

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With Signos, you can:

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• Monitor how your glucose responses change between summer and winter.
• Spot patterns in cravings, sleep, and stress.
• Personalize interventions to stay in “burn” mode even when the temperature drops.
• Stay on top of your metabolic health year-round to support your overall well-being.

The Bottom Line

Seasonal change affects metabolism more than most realize, shifting energy balance, hormones, and habits. By anticipating the body’s natural tendency toward “storage” in winter, you can build resilience with smart adjustments to food, movement, sleep, and stress management.

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Signos helps make these invisible shifts visible, offering real-time insights into how your metabolism responds to seasonal changes. With awareness and data-driven action, you can maintain steady metabolic health year-round.