Why the Thermostat is on Low
When transitioning to a low-carb diet, your body undergoes significant metabolic shifts that can affect its internal thermostat. In a normal, high-carbohydrate state, your body primarily uses glucose for energy. Digesting carbohydrates also generates a considerable amount of heat, a process known as diet-induced thermogenesis. When you cut carbs, this heat production decreases, contributing to a lower overall body temperature.
The Transition to Ketosis
The initial adaptation phase, often referred to as the “keto flu,” is where many people first experience feeling cold. Your body is moving from burning glucose to burning ketones (produced from fat) for fuel. This switch is not instantaneous and can cause a temporary dip in your metabolic rate as your cells become more efficient at using the new fuel source. This metabolic slowdown reduces the amount of heat your body generates, making you feel colder than usual.
Less Insulation from Body Fat
One of the most noticeable side effects of a low-carb diet is rapid weight loss, especially water weight, during the first few weeks. A significant portion of this weight comes from body fat, which acts as a natural insulator. As you lose this insulating layer, your body becomes more sensitive to external temperatures. The effect is particularly prominent in areas with less blood flow, such as the hands and feet, which may feel perpetually cold.
Electrolyte Imbalance and Dehydration
When carb intake is low, insulin levels drop. Low insulin signals the kidneys to excrete more sodium and water, which can lead to rapid dehydration. The loss of water and sodium can disrupt the balance of other electrolytes, including potassium and magnesium. This electrolyte imbalance affects circulation and can cause symptoms like chills, fatigue, and muscle cramps, all common symptoms of the 'keto flu'. Proper hydration and electrolyte replenishment are crucial for mitigating these effects.
Thyroid Function and Hormonal Changes
For some, a low-carb diet may impact thyroid function, which is a key regulator of metabolism and body temperature. Carbohydrates are involved in the conversion of the inactive thyroid hormone (T4) to the active form (T3). For some individuals, a significant reduction in carbohydrate intake can hinder this conversion, leading to lower levels of active T3. This can cause a temporary decrease in metabolic rate and an increased sensation of coldness. For those with pre-existing thyroid conditions, this effect can be more pronounced, making it essential to consult a healthcare professional.
Comparison of Causes for Feeling Cold
| Cause | Mechanism | Impact on Body Temperature | Duration |
|---|---|---|---|
| Metabolic Shift | Body switches from burning glucose to fat (ketosis), temporarily lowering metabolic rate. | Decreased internal heat production. | Temporary (days to weeks) during the adaptation phase. |
| Body Fat Loss | Reduced body fat, which acts as insulation, making you more sensitive to cold. | Less resistance to external cold, especially in extremities. | Persistent, especially with significant, rapid weight loss. |
| Electrolyte Imbalance | Reduced insulin leads to loss of sodium and water, affecting circulation. | Can cause chills, cold extremities, and other 'keto flu' symptoms. | Temporary (days to weeks) but can be mitigated by supplementation. |
| Reduced Thyroid Function | Severe carb restriction can decrease the conversion of inactive T4 to active T3. | Can lead to a persistent drop in metabolic rate and cold sensitivity. | Can be temporary, but prolonged issues require medical consultation. |
| Calorie Restriction | Eating too few calories forces the body to conserve energy by slowing metabolic processes. | Decreases overall heat production. | Variable, depending on the severity and duration of restriction. |
How to Combat the Cold
Increase Healthy Fats and Calories: Make sure you are eating enough calories, particularly from healthy fats, to provide your body with ample energy. Adequate fuel is essential for sustaining a healthy metabolic rate.
Replenish Electrolytes: Consume mineral-rich foods like leafy greens, avocados, and nuts, and consider adding salt to your food or using an electrolyte supplement. Drinking bone broth is also an excellent way to replenish lost sodium.
Stay Hydrated: Drink plenty of water throughout the day. Dehydration, compounded by electrolyte loss, can worsen feelings of coldness.
Engage in Light Activity: While your energy may be lower initially, light exercise like walking or yoga can help boost circulation and increase your core body temperature. Avoid overly strenuous workouts during the adaptation phase.
Consider a Less Drastic Carb Reduction: If you are particularly sensitive to the cold, consider a moderate low-carb approach rather than a very restrictive ketogenic one. Slowly phasing out carbohydrates can help your body adapt more smoothly.
Prioritize Sleep and Stress Management: Fatigue and irritability are common during the keto flu. Proper rest and stress reduction techniques, such as meditation, can help regulate hormone levels and improve overall well-being.
Conclusion
Feeling cold on a low-carb diet is a common, and usually temporary, side effect as your body adjusts to using fat for fuel. By understanding the underlying physiological changes—including metabolic slowdown, less body fat for insulation, electrolyte shifts, and potential impacts on thyroid function—you can take proactive steps to manage the symptoms effectively. Staying hydrated, replenishing electrolytes, and ensuring adequate calorie intake are key strategies for making the transition a warmer and more comfortable experience. As always, consult a healthcare professional if symptoms persist or are severe. Further information on optimizing a low-carb diet can be found through resources like Diet Doctor.
