Does your body get hot when in ketosis?: Unpacking the Link Between Ketosis and Body Temperature

October 26, 2025 •

4 min read

Research indicates that the body's metabolic shifts during ketosis can indeed alter thermoregulation, leading to noticeable changes in temperature. If you've been asking, "does your body get hot when in ketosis?", the answer is complex and depends heavily on your stage of adaptation to the diet.

Quick Summary

The ketogenic diet can cause changes in body temperature, including feeling hotter or colder. Fluctuations often correlate with the transition phase or fat adaptation, influenced by metabolic rate, brown fat activation, and electrolyte levels.

Key Points

Initial Coldness: In the early stages, the rapid loss of water and electrolytes can lead to chills and feeling cold, a common symptom of the "keto flu".
Adapted Warmth: As your body becomes fat-adapted, the efficient burning of fat for energy (thermogenesis) may increase your metabolic rate and cause you to feel warmer.
Electrolytes are Key: Maintaining proper hydration and replenishing lost electrolytes (sodium, potassium, magnesium) is crucial for regulating body temperature throughout the keto transition.
Brown Fat Activation: Some evidence suggests ketosis can activate brown adipose tissue, which is specialized in generating heat and contributes to the warming sensation.
Individual Variation: The effect on body temperature is not uniform; some people feel colder, some feel hotter, and some experience no change. Factors like metabolism and hydration play a big role.
Thyroid Hormones: Long-term ketosis can sometimes affect thyroid function, leading to reduced active thyroid hormone (T3), which can influence metabolic rate and temperature.

The ketogenic diet, a very low-carbohydrate, high-fat eating plan, pushes the body into a metabolic state called ketosis. While burning fat for fuel instead of glucose is the primary goal, this transition can cause a number of side effects, including surprising changes in how warm or cool you feel. The simple answer to whether your body gets hot in ketosis is that it can, but it’s part of a broader, more complex picture of metabolic adaptation.

The “Keto Flu” and the Initial Chill

Many people transitioning into ketosis experience the so-called “keto flu,” a period of side effects that can include fatigue, headaches, and flu-like symptoms. Interestingly, one of these common symptoms is feeling cold or having chills, particularly in the extremities. This cold sensation is largely a result of rapid fluid and electrolyte loss.

Carbohydrate depletion and water loss: In a non-keto state, the body stores carbohydrates as glycogen, which binds to a significant amount of water. When you restrict carbs, these glycogen stores are depleted, and the body flushes out the associated water. This diuretic effect leads to a rapid loss of fluid.
Electrolyte imbalance: Along with water, the body excretes vital electrolytes, including sodium, potassium, and magnesium. These minerals are crucial for a variety of bodily functions, including nerve and muscle function, as well as maintaining fluid balance. Their depletion can lead to symptoms like chills and muscle cramps.
Metabolic slowdown: During the very initial phases, your body is essentially in an energy crisis while it learns to switch fuel sources. This can lead to a temporary decrease in metabolic rate, which reduces internal heat production and makes you feel colder.

The Thermogenic Effect of Ketosis

As the body becomes "fat-adapted" and settles into a stable state of ketosis, some individuals report feeling warmer than usual. This can be attributed to several metabolic processes that generate heat, a phenomenon known as thermogenesis.

Increased metabolic rate: While the initial phase might cause a slowdown, a well-adapted ketogenic state can lead to a more efficient and potentially higher metabolic rate for some individuals. The process of oxidizing fat for energy can generate more heat as a byproduct compared to burning carbohydrates.
Brown adipose tissue (BAT) activation: Research suggests that a ketogenic diet can activate brown adipose tissue, or brown fat. Unlike white fat, which stores energy, brown fat burns calories to generate heat. The process of converting white fat into brown fat, known as "browning," enhances the body's thermogenic capabilities and contributes to a feeling of increased warmth.
Hormonal influences: The metabolic changes also involve hormonal shifts. For example, some studies suggest that ketosis might increase the activity of certain hormones that influence thermoregulation, including an increase in noradrenaline.

Early vs. Adapted Ketosis: A Comparison


Feature	Early Ketosis (Keto Flu)	Adapted Ketosis (Fat Adapted)
Primary Fuel Source	Transitioning from glucose to fat	Primarily fat and ketones
Body Temperature	Often feels cold or chilly	May feel warmer than normal
Metabolic Rate	Can temporarily decrease	May increase due to fat oxidation
Water/Fluid Balance	Rapid loss, leading to dehydration	Stabilized, with proper hydration
Electrolytes	Depleted levels are common	More balanced, with adequate intake
Energy Levels	Fatigue and lethargy are typical	Improved and sustained energy

Managing Temperature Fluctuations on Keto

Regardless of whether you feel hot or cold, it’s important to manage these symptoms to ensure a comfortable transition. Several strategies can help your body regulate its temperature more effectively while in ketosis.

Hydration is key: Drink plenty of water throughout the day, especially during the initial phase. This helps counteract the diuretic effect of ketosis and prevents dehydration.
Replenish electrolytes: Actively replace lost electrolytes to prevent cramps, headaches, and chills. This can be done by salting your food generously, using bone broth, or supplementing with keto-friendly electrolyte mixes. Sodium, potassium, and magnesium are the most important to focus on.
Adjust clothing layers: Dress in layers so you can easily adapt to changes in your body temperature. If you feel warm, you can shed a layer; if you feel cold, you can add one back on.
Ensure adequate calorie intake: While keto can suppress appetite, it's vital to eat enough fat to meet your energy needs. Insufficient calories can cause a further metabolic slowdown and drop in body temperature.
Stay active: Regular, low-intensity exercise can help boost your internal body temperature and improve circulation, which can combat feelings of coldness.
Allow for adaptation: The temperature fluctuations are often a temporary adjustment period. For many, these symptoms fade as the body becomes fully fat-adapted over several weeks.

The Role of Thyroid Function

It's also worth noting the potential link between ketosis and thyroid function. Some studies suggest that very low-carbohydrate diets can lead to a reduction in the active thyroid hormone, T3. The conversion of the inactive T4 to the active T3 hormone relies partly on carbohydrate availability, and reduced insulin levels on keto can suppress this conversion. This reduction in T3 can potentially lower the resting metabolic rate, which may exacerbate feelings of coldness. Regular monitoring of thyroid hormone levels is recommended for individuals on a long-term ketogenic diet, particularly those with pre-existing thyroid conditions.

Conclusion

Does your body get hot when in ketosis? The answer is that it can, especially after the initial adaptation phase when the body becomes more efficient at burning fat for energy through thermogenesis. However, it's more common to experience a temporary feeling of coldness during the initial transition (the "keto flu") due to fluid loss and electrolyte imbalance. Staying well-hydrated, actively replenishing electrolytes, and ensuring adequate fat intake are the best ways to support your body's temperature regulation. If symptoms are persistent or severe, consulting a healthcare professional is always the best course of action. Understanding these metabolic shifts can help you better navigate the ketogenic journey with confidence and comfort.

Frequently Asked Questions

The initial temperature fluctuations, often a cold sensation during the 'keto flu', typically last for a few days to a couple of weeks. Once your body becomes fat-adapted, usually within a few weeks, any warming effect from thermogenesis may become more stable.

During the initial phase of ketosis, the body flushes out stored glycogen and the associated water, leading to dehydration and a loss of electrolytes. This process, combined with a temporary dip in metabolic rate, is a common cause of feeling cold.

Not necessarily. Feeling cold, especially early on, is a normal physiological response to the metabolic shift and electrolyte loss, not necessarily a sign of malnutrition. Ensuring adequate hydration and electrolyte intake can help mitigate this.

Yes, some studies suggest very low-carb diets may lower active thyroid hormone (T3) levels, which could influence your metabolic rate and contribute to feeling cold. Consulting a doctor to monitor thyroid function is wise for long-term keto followers.

To regulate your temperature, focus on staying well-hydrated and replenishing lost electrolytes with mineral-rich foods, bone broth, or supplements. Adjusting your clothing and maintaining a balanced calorie intake also helps.

Yes, it is possible to experience both sensations. Some individuals report feeling chilly during the initial adaptation phase, followed by a period of feeling warmer once they are fully fat-adapted due to increased thermogenesis.

Yes, increased sweating, particularly at night, is a common side effect during the initial adaptation phase. This is partly due to the body expelling excess water as glycogen stores are depleted. Additionally, the odor of sweat can change due to the excretion of acetone, a ketone body.