The Science of Why Some People Run Hot and Others Always Feel Cold

It’s a scene familiar in almost every shared office and household: the thermostat war. One person is perfectly comfortable at 21°C. The person next to them is wearing a cardigan and still cold. Across the open-plan office, someone else is running a desk fan in January. Everyone thinks everyone else is wrong about what constitutes a reasonable temperature.

This isn’t arbitrary variation or personal preference—or not entirely. There are genuine physiological reasons why different people experience the same ambient temperature so differently, and the science is more interesting than “some people are just warm” or “just dress in layers.” Understanding what’s actually happening explains why the office thermostat dispute is essentially unwinnable.

How the Body Regulates Temperature

The human body is a remarkably precise thermostat, maintaining core temperature within roughly 0.5°C of its set point through a continuous process called thermoregulation. Core body temperature (typically measured at 37°C but varying slightly by individual and time of day) is not skin temperature—core temperature is the temperature of vital organs, and it’s what the body defends most aggressively.

The system works through two main mechanisms: heat generation and heat dissipation. Heat is generated primarily by metabolic processes—cellular respiration, muscle activity, and especially by brown adipose tissue (brown fat) in adults. Heat is dissipated primarily through skin, via radiation, convection, conduction, and evaporation (sweating).

The hypothalamus is the brain region that acts as the body’s thermostat. It receives temperature signals from thermoreceptors throughout the body—in the skin, in organs, and in the blood supplying the brain itself—and integrates them to determine whether to activate heat-conserving or heat-dissipating responses. When core temperature rises, the hypothalamus triggers sweating and vasodilation (expanding blood vessels near the skin surface to radiate more heat). When core temperature falls, it triggers shivering, vasoconstriction (constricting surface blood vessels to conserve heat), and activation of brown fat to generate additional heat.

The perception of cold or warmth in the environment is mediated by thermoreceptors in the skin—primarily TRP (transient receptor potential) channel proteins that respond to specific temperature ranges. These send signals to the brain that are interpreted as thermal sensation, which doesn’t necessarily correlate precisely with core temperature. You can feel cold while your core temperature is normal; you can feel warm while sweating to keep your core from overheating.

Metabolic Rate: The Primary Differentiator

Basal metabolic rate (BMR)—the rate at which your body burns energy at rest—is the single biggest factor in why people experience temperature differently. Someone with a higher BMR is generating more heat per unit time from metabolic processes and will therefore feel warmer at any given ambient temperature than someone with a lower BMR.

BMR varies substantially between individuals, driven by several factors:

Body composition. Muscle tissue is significantly more metabolically active than fat tissue—muscle burns approximately three times as many calories per unit mass at rest. People with more muscle mass have higher BMRs and generate more resting heat. This is one reason why people who exercise regularly often feel warmer at rest—increased muscle mass raises the metabolic floor.

Body size. Larger bodies have more total metabolic tissue and generate more absolute heat, but body size also affects the surface area-to-volume ratio, which governs how efficiently heat is lost. Smaller bodies have a higher surface area-to-volume ratio and lose heat more efficiently—which is part of why smaller people (including women, on average, who have somewhat smaller bodies and less muscle mass) often feel colder in the same environment than larger people.

Thyroid function. The thyroid gland produces hormones (primarily T3 and T4) that directly regulate metabolic rate. Hyperthyroidism—excess thyroid hormone production—increases BMR, often dramatically, and produces heat intolerance as a characteristic symptom. Hypothyroidism—insufficient thyroid hormone—decreases BMR and is commonly associated with feeling cold persistently, cold intolerance, and inability to stay warm. Thyroid function is one of the first things a doctor will investigate if someone consistently feels cold without obvious explanation.

Age. Metabolic rate typically declines with age, particularly after the fourth decade. Older adults often feel colder in environments that felt comfortable decades earlier, in part because of this metabolic change and in part because of reduced subcutaneous fat and changes in blood vessel regulation.

Peripheral Circulation and the Role of Blood Flow

How much blood reaches the extremities has an outsized effect on how cold or warm hands and feet feel—which in turn influences overall thermal comfort perception substantially. Poor peripheral circulation means less warm blood reaching the fingers and toes, producing cold extremities even when core temperature is normal.

Raynaud’s phenomenon is an extreme example: in affected individuals, cold or emotional stress triggers dramatic vasoconstriction in the fingers, which turn white or blue and feel intensely cold. Raynaud’s affects approximately 5–10% of the population, with higher prevalence in women. Milder forms of peripheral vasoconstriction—not severe enough to classify as Raynaud’s—are common and explain why many people have chronically cold hands and feet even in comfortable environments.

Iron deficiency anaemia affects peripheral circulation through a different mechanism: insufficient red blood cells means less efficient oxygen delivery, which reduces cellular energy production throughout the body including in peripheral tissues. Cold intolerance is a recognised symptom of iron deficiency anaemia, and it’s one of the more common medical explanations for persistent cold feeling in otherwise healthy young adults, particularly women (due to menstrual iron losses).

Blood pressure also plays a role. Low blood pressure reduces blood flow to peripheral tissues, contributing to cold extremities. People who are constitutionally hypotensive (run a naturally low blood pressure) often have perpetually cold hands, which they may not connect to their cardiovascular baseline.

Sex Differences in Thermal Comfort

The stereotype that women feel colder than men is borne out by research, but the underlying reasons are more nuanced than usually acknowledged.

Average differences in body size and composition between men and women account for much of the difference: women, on average, have less muscle mass and therefore lower BMR, and also have a higher surface area-to-volume ratio that facilitates heat loss. These are population-level averages with enormous individual variation, but they explain a meaningful portion of the aggregate difference.

Hormonal influences are also significant. Oestrogen promotes peripheral vasoconstriction, which reduces blood flow to extremities—contributing to cold hands and feet. This is one reason why thermal discomfort varies across the menstrual cycle and changes substantially during perimenopause and menopause. Progesterone, by contrast, slightly elevates core body temperature, which is why basal body temperature tracking is used in fertility awareness methods.

There’s also emerging evidence that the thermal comfort range differs slightly by sex—that women have a somewhat narrower comfortable temperature range and a slightly different optimal temperature, which has implications for workplace and building design. A widely-cited 2015 study argued that standard office temperature guidelines were based on a metabolic model calibrated for a 40-year-old 70kg male, and that women on average would be comfortable at slightly warmer temperatures. The precise numbers are debated, but the underlying point—that one-size-fits-all thermal environments serve some people better than others—is well supported.

Acclimatisation and Adaptation

Bodies adapt to thermal environments over time. People who spend extended periods in cold climates develop physiological adaptations that improve cold tolerance: increased brown adipose tissue activity (brown fat generates heat by “uncoupling” cellular respiration to produce heat rather than ATP), altered vasoconstriction thresholds, and improved insulating subcutaneous fat distribution in some cases. These adaptations are reversible—move somewhere warmer and the cold adaptations gradually diminish.

Conversely, people acclimatised to warm environments develop better heat dissipation efficiency: earlier sweating onset at lower temperatures, greater total sweat capacity, and altered salt concentration in sweat that preserves electrolytes. Athletes training in heat develop these adaptations deliberately to improve performance in warm conditions.

The practical implication: moving between climates is genuinely physically difficult, not just psychologically uncomfortable. It takes several weeks to fully acclimatise to a significantly different temperature environment, and the discomfort during that period reflects real physiological stress, not weakness or poor tolerance.

The Psychological and Perceptual Dimension

Thermal sensation is not purely physical—it has significant perceptual and psychological components. The same objective temperature can feel different depending on:

Humidity. High humidity impairs evaporative cooling (sweating), making the same temperature feel hotter. Low humidity increases evaporative cooling, making the same temperature feel cooler. “Feels like” temperature indices attempt to account for this, but individual variation in sweat production means the same “feels like” index affects different people differently.

Wind. Wind increases convective heat loss from the skin surface, making the same temperature feel colder—the wind chill effect. People with more exposed skin surface (shorter hair, less clothing) experience this more intensely.

Context and attention. Thermal comfort is sensitive to what you’re doing. Sedentary work produces less metabolic heat than active work; the same ambient temperature feels colder when sitting still than when moving. Mentally demanding tasks that produce cognitive absorption can reduce thermal discomfort perception. Stress and anxiety alter peripheral blood flow and can exacerbate cold sensation.

Genetics. Variation in TRP channel function—the temperature-sensitive proteins in peripheral nerve endings—is partly genetic, meaning some variation in thermal sensitivity at the sensory level is heritable. This is an active area of research and explains why some individuals are genuinely more sensitive to thermal stimuli than others in ways that don’t map neatly to metabolic rate or circulation.

When to Take Thermal Intolerance Seriously

Most variation in thermal comfort is normal physiological diversity. But some cases warrant medical attention:

Persistent cold intolerance that is new or worsening—especially with fatigue, weight gain, dry skin, or cognitive slowing—may indicate hypothyroidism and is worth investigating with a simple blood test. Cold intolerance with classic Raynaud’s colour changes (white or blue fingers in cold) is manageable but worth evaluating. Cold intolerance alongside fatigue, pale skin, and breathlessness may indicate anaemia.

Heat intolerance that is new or worsening—especially with unexplained weight loss, heart palpitations, anxiety, or tremor—may indicate hyperthyroidism, which is treatable but requires medical diagnosis.

For most people, the answer is not a medical explanation but rather the compounded reality of metabolic rate, body composition, circulation, hormones, and adaptation—a genuinely complex set of factors that ensures no two people will agree on the right thermostat setting. The office thermostat will remain disputed. At least now you know why.