For many people, the ketogenic diet is a significant change from their usual eating patterns. The body's energy system, which has long relied on glucose from carbohydrates, must undergo a fundamental shift to use fat and ketones as its primary fuel source. This metabolic transition, while beneficial for many health goals, can lead to some unexpected side effects, including feeling unusually cold.
The metabolic shift explained
When you dramatically reduce your carbohydrate intake, your body's glycogen stores are quickly depleted. This triggers the liver to start breaking down fat for energy, a process called ketogenesis, which produces ketone bodies. Your body's cells, including your brain, learn to use these ketones for fuel. This major change in fuel source can temporarily disrupt your body's normal thermoregulation, the process by which it maintains a stable internal temperature.
Why the temperature drops during keto-adaptation
Several factors contribute to the sensation of being cold during the initial weeks of ketosis, a period often referred to as the 'keto flu'.
- Lowered metabolic rate: The body's metabolism can slow down as a response to the dietary change, especially if you are also consuming fewer calories for weight loss. This is a survival mechanism where the body conserves energy, leading to a drop in your resting metabolic rate (RMR) and reduced heat production.
- Thyroid hormone adjustments: Low-carbohydrate diets can impact thyroid function, specifically by reducing the levels of the active thyroid hormone, T3. Since the thyroid is a major regulator of metabolism and body temperature, this temporary reduction can contribute to feeling cold.
- Dehydration and electrolyte imbalance: During the first few days of ketosis, the body flushes out excess water. This rapid fluid loss can lead to dehydration and a depletion of essential electrolytes like sodium, potassium, and magnesium. Electrolytes are vital for many bodily functions, including regulating temperature. A deficiency can make you feel chilly or cause chills.
- Redirected blood flow: As the body shifts its energy priorities, blood flow can be temporarily redirected to other areas, away from the extremities. This can cause cold hands and feet, a common complaint during the early phase of ketosis.
Managing cold intolerance on keto
For most people, the cold sensation during keto is temporary and resolves as the body becomes more efficient at using fat for fuel. However, if the feeling persists, there are several strategies you can employ.
Practical solutions for staying warm
- Prioritize proper hydration and electrolytes: This is arguably the most critical step. Ensure you are drinking plenty of water and actively replenishing electrolytes. You can achieve this by adding a pinch of salt to your water, drinking bone broth, or consuming electrolyte supplements.
- Ensure sufficient calorie intake: If you're on a very low-calorie ketogenic diet for weight loss, your metabolic rate might drop more significantly. Make sure you are consuming enough calories and not engaging in overly restrictive eating, which can be counterproductive.
- Increase healthy fat intake: Some sources suggest that consuming enough healthy fats can help keep your energy levels up and improve metabolic efficiency. Adding sources like avocado, olive oil, and nuts can help.
- Stay active with moderate exercise: Light physical activity, like walking, can help boost circulation and generate heat without putting excessive stress on your body.
- Wear warmer clothing and drink hot beverages: Simple measures like bundling up in an extra layer or sipping on a cup of warm tea can provide immediate relief from the cold sensation.
Initial ketosis vs. Fat-adapted state: A comparison of body temperature
| Feature | Initial Ketosis (Keto-Adaptation) | Fat-Adapted State (Long-Term Ketosis) |
|---|---|---|
| Primary Fuel Source | Transitioning from glucose to fat and ketones | Primarily fat and ketones |
| Metabolic Response | Body may lower its resting metabolic rate to conserve energy, mimicking a starvation signal. | Metabolism stabilizes, with many individuals reporting increased warmth due to enhanced thermogenesis. |
| Fluid Balance | Rapid loss of water and electrolytes, leading to dehydration and chills. | Hydration and electrolyte levels stabilize as the body adjusts to the low-carb environment. |
| Reported Body Temp | Many report feeling colder, especially in extremities, as blood flow may be redirected. | Body temperature often returns to normal or may even feel slightly warmer for some individuals. |
| Common Side Effects | 'Keto flu' symptoms, including cold intolerance, fatigue, headaches, and brain fog. | Side effects subside, with many experiencing increased energy and mental clarity. |
When to consult a healthcare professional
While feeling cold during keto-adaptation is common, it's important to consult a doctor if the symptom is excessive, persists long-term, or is accompanied by other worrying signs. These could indicate underlying issues, such as a more significant thyroid problem or nutritional deficiency. A medical professional can also help determine if a less restrictive form of a low-carb diet is better suited for your health needs, especially for those with existing conditions like hypothyroidism. An excellent source for further research on the ketogenic diet's impact on metabolism can be found on the National Institutes of Health website at https://www.ncbi.nlm.nih.gov/books/NBK499830/.
Conclusion
In summary, the sensation of feeling cold while on a keto diet is a well-documented side effect, particularly during the initial phase of metabolic adaptation. This temporary dip in body temperature is often a result of the body's energy shift, electrolyte imbalance, or a reduction in metabolic rate. For most individuals, these symptoms resolve as the body becomes more efficient at using ketones for fuel. By prioritizing hydration, replenishing electrolytes, and ensuring adequate calorie intake, you can effectively manage this temporary chill. For those with pre-existing conditions or persistent symptoms, consulting a healthcare provider is the safest course of action.
