If you’re comfortable in a cool room while everyone around you is reaching for a sweater, your body is simply producing or retaining heat more effectively than theirs. This isn’t unusual or concerning in most cases. The gap comes down to a mix of metabolism, body composition, hormones, genetics, and even what you ate for lunch. Here’s what’s actually going on under the surface.
Your Metabolic Rate Sets the Baseline
Your basal metabolic rate, the energy your body burns just to keep you alive at rest, is one of the strongest predictors of how you handle cold. Every calorie your body burns releases heat as a byproduct. People with a higher metabolic rate produce more of this background heat constantly, which means they start from a warmer baseline when the temperature drops.
Research on cold tolerance has shown that people with a high basal metabolic rate don’t need to ramp up heat production much when exposed to cold. Instead, their bodies simply reduce blood flow to the skin to hold onto the heat they’re already generating. People with a lower metabolic rate, on the other hand, have to actively crank up their internal furnace, burning more energy and often shivering sooner. So if your metabolism runs hot, you may genuinely not notice a chill that sends someone else scrambling for a jacket.
Muscle Mass Is a Built-In Heater
Skeletal muscle makes up roughly 45% to 55% of total body mass in most people and is the largest contributor to your basal metabolic rate. It’s also your primary heat-producing organ. Muscle generates warmth in two ways: through movement (including the involuntary contractions of shivering) and through a quieter process where muscle cells burn energy to cycle calcium across internal membranes, releasing heat without any visible movement at all.
This means someone with more muscle mass is generating more heat around the clock, even sitting perfectly still. If you’re more muscular than the people around you, that alone could explain the difference in comfort. Body fat also plays a role, but in a different way. Fat tissue doesn’t produce much heat on its own. It acts primarily as insulation, slowing heat loss through the skin. So a person with both significant muscle and some body fat has a double advantage: more internal heat production plus better retention of that heat.
Brown Fat: Your Hidden Warming System
Not all fat is the same. Brown adipose tissue is a specialized type of fat whose only real job is to burn calories and produce heat. It does this by short-circuiting the normal energy-production process in its cells, diverting energy that would normally be stored as fuel and releasing it as warmth instead. This is called non-shivering thermogenesis, and it lets your body warm up without the discomfort of shivering.
For a long time, scientists believed brown fat disappeared after infancy. It doesn’t. Functional brown fat can be detected in over 50% of adults when it’s activated, though levels vary considerably based on age, sex, body fat percentage, and how much cold exposure you get regularly. Young, lean women tend to have the most detectable brown fat. If you have more active brown fat than the people around you, your body has a warming mechanism they may lack.
Here’s what’s interesting: brown fat activity increases with regular cold exposure. In one study, men who spent two hours a day in cold conditions, five days a week for four weeks, increased their brown fat volume by 45% and its heat-producing capacity by 182%. At the same time, their shivering decreased by 21%. Their bodies had shifted from a brute-force warming strategy (shivering) to a more efficient one (brown fat activation). If you spend more time outdoors in cool weather than the people around you, your body may have already made this adaptation.
Thyroid Hormones Control the Thermostat
Your thyroid gland acts like a master dial for your metabolic rate. It releases hormones that stimulate energy-burning pathways throughout your body, and those pathways generate heat. Thyroid hormones also amplify your body’s response to its own adrenaline-like signals, making you more reactive to cold exposure when you need to warm up. They even directly boost brown fat activity.
Someone whose thyroid is naturally on the higher end of normal will run warmer than someone on the lower end. And if your thyroid is genuinely overactive, a condition called hyperthyroidism, heat intolerance becomes a hallmark symptom. People with hyperthyroidism often feel uncomfortably warm in rooms others find pleasant. Other signs include unintentional weight loss, a rapid heartbeat, tremors, anxiety, and warm, moist skin. If your warmth comes alongside any of these, it’s worth getting your thyroid levels checked with a simple blood test.
Your Cold Sensors Are Genetically Tuned
Feeling cold isn’t just about your core temperature. It’s also about how your nerve endings detect and report temperature to your brain. The main cold-sensing receptor on your skin cells is a protein channel that activates when temperatures drop, sending a “cold” signal up to the brain. It’s the same receptor that responds to menthol, which is why peppermint feels cool on your skin.
The sensitivity of this receptor varies from person to person based on genetics. In animal studies, researchers have shown that a single point mutation in the gene for this receptor can virtually abolish the ability to sense cool temperatures. Mice carrying this mutation couldn’t distinguish between cool and neutral surfaces. While that’s an extreme example, subtler genetic variations in the same receptor exist across the human population. If your version of this receptor is less sensitive, you would genuinely perceive the same temperature as less cold than someone standing right next to you, even if your core body temperatures were identical.
Gender Plays a Real Role
If you’re a man wondering why the women around you seem cold all the time, or if you’re a woman who runs warmer than your female friends, there are measurable biological reasons for gender differences in thermal comfort. Men tend to have higher basal metabolic rates, largely because they carry more muscle mass on average. Women tend to have lower skin temperatures in their extremities (hands and feet), which makes the subjective experience of cold more noticeable.
Research on thermal comfort thresholds has found that women are more sensitive to cooling environments than men, and that men have a wider range of temperatures they find acceptable. These aren’t just cultural preferences. They reflect real differences in metabolic heat production, body surface area relative to mass, and how blood flow is distributed to the skin. Office buildings, incidentally, have historically set their thermostats based on the metabolic rate of a 40-year-old man, which is part of why thermal comfort disputes in shared spaces are so common.
What You Eat Generates Heat Too
Digesting food raises your core temperature. This effect, called diet-induced thermogenesis, varies dramatically depending on what you eat. Protein is the most thermogenic macronutrient by a significant margin. Your body uses roughly 20% to 30% of the calories in protein just to digest and process it, and that energy is released as heat. Carbohydrates and fat produce a much smaller thermal bump.
If you’ve recently eaten a high-protein meal and the person next to you hasn’t eaten in hours, or ate a lighter, fat-heavy snack, that alone could account for a noticeable difference in how warm you feel. It’s a temporary effect, lasting a few hours after eating, but it’s a real one.
Your Internal Clock Shifts Temperature Too
Your core body temperature isn’t fixed. It follows a circadian rhythm, rising and falling by about 0.7°C to 1.3°C (roughly 1.3°F to 2.3°F) over the course of a day. It typically peaks in the late afternoon or early evening, around 10 hours after you wake up, and bottoms out in the early morning hours while you sleep.
This means the same room can feel comfortable to you at 4 PM and chilly at 10 PM, even if the thermostat hasn’t changed. It also means that if your circadian rhythm is shifted relative to someone else’s (say, you’re a natural early riser and they’re a night owl), you could be at different points in your temperature cycle while sitting in the same room. Your body may be near its daily peak while theirs is still climbing.
Cold Acclimation Changes Your Tolerance
If you spend regular time in cold environments, whether through outdoor work, cold-weather exercise, or simply keeping your home cooler, your body adapts. The four-week cold exposure study mentioned earlier is a good illustration: participants didn’t produce more total heat after acclimation, but they shifted how they produced it. Their brown fat became more active, their muscles shivered less, and they were subjectively more comfortable at the same cold temperature.
This is a trainable response. People who swim in cold water, work outdoors through winter, or routinely expose themselves to cool temperatures develop measurably better cold tolerance over weeks to months. If your lifestyle involves more cold exposure than the people around you, your body has likely recalibrated what it considers “cold enough to respond to,” and the threshold is simply lower than theirs.