How to get energy when cutting carbs? Your guide to sustained power on a low-carb diet

October 11, 2025 •

3 min read

Approximately 40% of American adults are obese, with many exploring low-carb diets to improve their health. For those reducing carbohydrates, a common hurdle is the initial drop in energy, often dubbed the "keto flu". Learning how to get energy when cutting carbs is crucial for a successful and sustainable dietary transition.

Quick Summary

This guide provides practical strategies for maintaining energy on a low-carb diet by explaining the metabolic shift to fat-burning. It covers the importance of healthy fats, proper electrolyte balance, and managing the initial adaptation phase to avoid fatigue.

Key Points

Increase Healthy Fats: Replenish calories and provide sustained energy by eating more avocados, nuts, seeds, and fatty fish to compensate for reduced carbs.
Balance Electrolytes: Replenish sodium, potassium, and magnesium with bone broth, leafy greens, and supplements to combat fatigue and muscle cramps from water loss.
Stay Hydrated: Drink plenty of water to prevent dehydration, which is common when first cutting carbs and flushing electrolytes.
Moderate Exercise: Opt for low-intensity workouts initially to help your body adapt to fat-burning and avoid exhaustion during the transition period.
Prioritize Quality Sleep: Aim for 7-8 hours of sleep per night to allow your body to recover and regulate energy hormones, reducing fatigue.
Mindful Protein Intake: Eat moderate amounts of quality protein to support muscle health without triggering gluconeogenesis, which can hinder ketosis.

Understanding the Energy Shift: From Carbs to Fat

When you drastically reduce carbohydrate intake, your body is forced to find an alternative fuel source. Normally, it relies on glucose from carbohydrates. Without a steady supply of carbs, your liver begins converting fat into compounds called ketones, which are used for energy by the brain and body. This metabolic state is known as nutritional ketosis. However, the initial transition period, often lasting a few days to a couple of weeks, can cause temporary fatigue, headaches, and brain fog as your body adapts. The key to regaining energy is to support this metabolic shift through specific dietary and lifestyle adjustments.

Prioritize Healthy Fats for Fuel

One of the most common mistakes people make when cutting carbs is failing to increase their fat intake. Fat is the primary energy source in a low-carb, ketogenic diet and provides more than double the energy per gram compared to carbs. Ensuring you consume enough healthy fats is critical for sustained energy levels.

Avocado and Avocado Oil: Rich in monounsaturated fats, avocados provide a steady stream of energy and are excellent for satiety.
Nuts and Seeds: Almonds, macadamia nuts, pecans, and chia seeds are packed with healthy fats, protein, and fiber.
MCT Oil: Medium-chain triglyceride oil, often derived from coconut oil, is rapidly converted into ketones by the liver, providing a quick and efficient energy boost.
Fatty Fish: Salmon, mackerel, and sardines are excellent sources of omega-3 fatty acids and healthy fats for fuel.

The Critical Role of Electrolytes and Hydration

During the initial phase of carb restriction, your body sheds water and with it, essential electrolytes like sodium, potassium, and magnesium. This loss is a major contributor to the fatigue and muscle cramps associated with the "keto flu".

Sodium: Increase your intake by adding more salt to your food or drinking bone broth.
Potassium: Include potassium-rich, low-carb foods like avocados, leafy greens (spinach, kale), and salmon.
Magnesium: Incorporate foods like nuts, seeds, and leafy greens. A magnesium supplement may also be beneficial.

Staying well-hydrated is equally important, as it helps prevent dizziness and fatigue. Aim to drink plenty of water throughout the day.

Optimizing Your Low-Carb Lifestyle for Energy

Strategic Protein Intake

Protein is essential for muscle maintenance and recovery, especially if you're exercising. However, eating too much protein can cause excess amino acids to be converted into glucose in a process called gluconeogenesis, which can stall ketosis. A moderate protein intake is key. Focus on quality sources like grass-fed beef, poultry, eggs, and fish.

Moderate Exercise and Quality Sleep

Initially, intense workouts can feel difficult on a low-carb diet. It's wise to start with low-intensity, steady-state (LISS) cardio like walking, jogging, or cycling as your body adapts to using fat for fuel. As you become more fat-adapted, your endurance may improve.

Sleep is vital for energy regulation and metabolic function. Poor sleep can disrupt hormone levels, leading to increased cravings and fatigue. Aim for 7-8 hours of quality sleep per night. For some, adding a small portion of low-glycemic carbs like berries or sweet potatoes in the evening can help with sleep.

Comparison of Energy Sources: Carbs vs. Ketones


Feature	Glucose (Carbohydrates)	Ketones (Fats)
Primary Source	High-carb foods: breads, pasta, sugar, grains	Healthy high-fat foods: avocados, nuts, oils, fatty fish
Availability	Quick-release energy; short-term bursts	Slow, sustained energy; long-term endurance
Mental Clarity	Can cause blood sugar spikes and crashes, leading to "brain fog"	Provides a steady, consistent fuel source for the brain
Metabolic State	Standard metabolism, relies on insulin to process glucose	Nutritional ketosis, relies on ketone bodies from fat
Satiety	Can lead to hunger and cravings after spikes and crashes	High-fat intake promotes greater satiety and reduced hunger

A Final Word on Consistency and Patience

Successfully transitioning to a low-carb diet requires patience. The initial energy slump is temporary and a sign that your body is shifting its fuel source. By focusing on nutrient-dense, healthy fats, maintaining proper hydration and electrolyte levels, and optimizing your sleep and exercise, you can overcome this hurdle and enjoy sustained, stable energy levels. Always listen to your body and consult a healthcare professional for personalized advice, especially if you have underlying health conditions or are on medication. The ultimate goal is a sustainable diet that makes you feel your best, not one that leaves you feeling depleted. For additional resources and recipes, the Heart Research Institute offers a comprehensive guide to low-carb eating.

Frequently Asked Questions

The fatigue, often called the "keto flu," is caused by your body transitioning from burning glucose for energy to using fat and ketones. It's a temporary adjustment period as your metabolism adapts.

Excellent sources of healthy fats include avocados, nuts (like almonds and macadamias), seeds (chia, flax), olive oil, and fatty fish such as salmon.

You can increase your electrolyte intake by adding extra salt to food, drinking bone broth, and eating potassium-rich foods like avocados and leafy greens. Consider a magnesium supplement if needed.

Yes, moderate protein helps maintain muscle mass and provides a steady fuel source. However, consuming excessive protein can be converted to glucose, which may counteract the goals of a low-carb diet.

Yes, but it's recommended to start with low-intensity, steady-state (LISS) exercises like walking or cycling while your body adapts. High-intensity exercise may feel difficult initially.

To prevent or minimize symptoms, ensure adequate hydration, actively replenish electrolytes, and ease into the diet gradually instead of cutting carbs abruptly.

Most people find their energy levels stabilize and even increase after the initial adaptation period, which can last anywhere from a few days to a few weeks, as their body becomes efficient at burning fat for fuel.