Fasting can lower your body temperature, often making you feel cold due to reduced metabolism and decreased heat production.
Why Does Fasting Affect Body Temperature?
Fasting triggers a series of changes in your body’s metabolism. When you stop eating, your body shifts from using glucose derived from food to burning stored fat for energy. This metabolic switch is efficient but slower, causing your overall energy expenditure to drop. Since heat is a byproduct of metabolism, a slower metabolic rate means less internal heat generation.
Your body’s thermostat—controlled by the hypothalamus—responds to these changes by conserving energy. One way it does this is by reducing blood flow to the skin and extremities, which can make you feel cold even if the ambient temperature hasn’t changed. This physiological response helps preserve core body temperature but leaves your hands and feet feeling chilly.
The Role of Hormones in Cold Sensation During Fasting
Hormones like thyroid hormones and insulin play a significant role in regulating metabolism and body heat. During fasting, insulin levels drop because there’s less glucose in the bloodstream. Lower insulin signals the body to slow down certain processes, including heat production.
Thyroid hormones, which regulate how fast cells burn energy, also tend to decrease during prolonged fasting or calorie restriction. This reduction slows down metabolism further and contributes to feeling cold. Additionally, cortisol levels may rise during fasting stress, altering how your body manages energy and temperature.
How Metabolic Rate Drops During Fasting
Metabolic rate is the speed at which your body burns calories for energy. When you fast, your metabolic rate decreases as a survival mechanism to conserve energy stores. This drop can be as much as 10-20% depending on the length of the fast and individual factors like age, sex, and body composition.
With fewer calories being burned each minute, less heat is produced internally. That’s why many people report feeling colder during fasting periods compared to when they are eating normally.
Energy Conservation: The Body’s Cold Response
The human body prioritizes keeping vital organs warm during fasting. To do this efficiently, it reduces blood flow to less critical areas like skin and limbs—a process called peripheral vasoconstriction. This limits heat loss but results in cold hands and feet.
Shivering is another response that generates heat through muscle activity but usually occurs only when core temperature drops significantly. Mild cold feelings from fasting typically don’t trigger shivering but can still be uncomfortable.
Does Fasting Make You Cold? The Science Behind It
Studies measuring core body temperature during fasting show a modest decline of about 0.5°C (0.9°F) after 24-48 hours without food intake. This drop might seem small but is enough for many individuals to notice a chill.
Research also indicates that prolonged calorie restriction leads to adaptive thermogenesis—a process where the body becomes more efficient at using energy and produces less heat overall. This adaptation helps conserve fat stores during times of scarcity but makes the person feel colder than usual.
Comparing Short-Term vs Long-Term Fasting Effects
Short-term fasts (12-24 hours) often cause mild cold sensations due to immediate metabolic slowing and hormonal shifts. However, these effects are reversible once eating resumes.
Longer fasts or repeated intermittent fasting can lead to more pronounced drops in thyroid hormone levels and sustained metabolic slowdown. Over time, this makes cold sensitivity more noticeable and persistent until normal eating patterns resume.
How Individual Factors Influence Cold Sensitivity During Fasting
Not everyone experiences cold feelings equally while fasting. Several factors influence this sensation:
- Body Fat Percentage: Fat acts as insulation against cold; leaner individuals may feel colder faster.
- Age: Older adults tend to have slower metabolisms and may experience stronger cold sensations.
- Gender: Women often report feeling colder than men due to hormonal differences affecting circulation.
- Environmental Conditions: Cooler ambient temperatures amplify fasting-related cold sensations.
- Hydration Status: Dehydration can impair circulation, worsening feelings of coldness.
Understanding these variables helps explain why some people breeze through fasts without discomfort while others struggle with chills.
The Impact of Activity Level on Feeling Cold While Fasting
Physical activity generates heat through muscle contractions, helping maintain warmth during fasting periods. Sedentary behavior combined with fasting increases the likelihood of feeling cold since less internal heat is produced.
Light exercise or movement can counteract some of the chilling effects by boosting circulation and stimulating metabolism even without food intake.
Nutritional Strategies to Combat Cold Sensations When Fasting
You can ease fasting-induced chills with smart nutritional choices before or after your fast:
- Eat warming foods: Spices like ginger, cayenne pepper, and cinnamon promote blood flow and warmth.
- Stay hydrated: Drinking warm herbal teas or water helps maintain circulation.
- Adequate electrolyte intake: Sodium, potassium, magnesium support nerve function affecting thermoregulation.
- Avoid caffeine excess: Though stimulating initially, caffeine can cause dehydration that worsens cold feelings.
These tactics don’t break your fast if timed properly but provide comfort before or after fasting windows.
The Role of Refeeding in Restoring Body Temperature
Once you break a fast with balanced nutrition rich in carbohydrates and proteins, insulin levels rise again signaling cells to ramp up metabolism. This increase restores normal heat production quickly.
Refeeding also replenishes glycogen stores that support thyroid hormone activity—further stabilizing your internal thermostat.
The Science Table: Metabolic Changes & Temperature Effects During Fasting
| Fasting Duration | Metabolic Rate Change (%) | Average Core Temp Drop (°C) |
|---|---|---|
| 12-24 hours | -5% to -10% | -0.2°C to -0.4°C |
| 24-48 hours | -10% to -15% | -0.4°C to -0.6°C |
| >48 hours (Prolonged) | -15% to -20% | -0.5°C to -0.8°C+ |
This data highlights how longer fasting periods deepen metabolic slowdown and temperature reduction—explaining why chills intensify with extended food deprivation.
Coping Mechanisms Beyond Nutrition for Cold While Fasting
Besides what you eat or drink around fasting times, several practical steps help manage chills:
- Dress warmly: Layer clothing especially on extremities like hands and feet.
- Avoid drafts: Keep living spaces warm since external cold worsens internal chill sensations.
- Mild exercise: Walking or stretching boosts circulation without breaking fast.
- Meditation & breathing exercises: Stress reduction lowers cortisol spikes that may affect temperature regulation.
These lifestyle tweaks complement physiological adjustments during fasting for better comfort.
Key Takeaways: Does Fasting Make You Cold?
➤ Fasting lowers metabolism temporarily.
➤ Reduced calorie intake can decrease body heat.
➤ Blood flow may shift, causing cold extremities.
➤ Hydration levels impact temperature regulation.
➤ Individual responses to fasting vary widely.
Frequently Asked Questions
Does fasting make you cold because of lower metabolism?
Yes, fasting slows down your metabolism as your body switches from using glucose to burning stored fat. This slower metabolic rate produces less internal heat, which can make you feel colder than usual during fasting periods.
Why does fasting make you cold even if the room temperature is warm?
Fasting causes your body to reduce blood flow to the skin and extremities to conserve energy. This peripheral vasoconstriction makes your hands and feet feel cold, even if the ambient temperature hasn’t changed.
How do hormones affect feeling cold during fasting?
Hormones like thyroid hormones and insulin decrease during fasting, slowing metabolism and heat production. Additionally, increased cortisol levels may alter energy management, contributing to the sensation of feeling cold.
Can the length of a fast influence how cold you feel?
Yes, longer fasts tend to cause a greater drop in metabolic rate—sometimes by 10-20%—which reduces heat production more significantly. This often results in a stronger sensation of cold over extended fasting periods.
Does fasting cause shivering as a response to feeling cold?
Shivering can occur during fasting as a way for your body to generate heat through muscle activity. It’s a natural response aimed at maintaining core temperature when internal heat production is reduced.
The Final Word: Does Fasting Make You Cold?
Yes—fasting naturally slows metabolism reducing internal heat production causing many people to feel colder than usual especially in longer fasts or when combined with low body fat or cooler environments.
This chilliness stems from hormonal shifts lowering thyroid activity plus reduced blood flow conserving core warmth at the expense of peripheral warmth—resulting in those familiar cold hands and feet sensations during food deprivation periods.
However, this effect is temporary; normal eating restores metabolic rate quickly along with comfortable warmth levels again.
Understanding these mechanisms helps set realistic expectations for anyone trying intermittent or extended fasts so they’re prepared rather than caught off guard by this common side effect.