The ketogenic diet, a high-fat, moderate-protein, and very low-carbohydrate eating plan, has gained significant popularity. Simultaneously, intermittent fasting, an eating pattern that cycles between periods of eating and voluntary fasting on a regular schedule, has also become a widespread wellness trend. Combining these two approaches, often referred to as "keto fasting" or "keto intermittent fasting," is believed by some to amplify their individual benefits. While both strategies have demonstrated short-term advantages such as fat loss, improved blood sugar control, and enhanced metabolic health, it's essential to understand the potential benefits, risks, and practical considerations of integrating them.
Understanding the Ketogenic Diet
The ketogenic diet, with roots tracing back to the 1920s, involves drastically reducing carbohydrate intake and increasing fat consumption. This metabolic shift forces the body to transition from primarily burning glucose (derived from carbohydrates) for energy to utilizing fat as its primary fuel source. Typically, the keto diet consists of obtaining only about 5% of daily calories from carbohydrates, emphasizing low-carb, non-starchy vegetables and limited amounts of leafy greens. This can mean restricting total carb intake to less than 50 grams per day. For context, this is roughly equivalent to the amount of carbohydrates found in a cup of white rice.
By excluding carb-rich foods like grains, beans, fruits, and starchy vegetables, the keto diet compels the body to break down fats into molecules called ketones. These ketones then serve as an alternative fuel source, a metabolic state known as ketosis.
Intermittent Fasting: A Primer
Intermittent fasting (IF) is not a diet per se, but rather an eating pattern. It revolves around cycling between periods of eating and voluntary fasting on a regular schedule. Unlike the keto diet, IF does not dictate what foods to eat, but rather when to eat them. Popular intermittent fasting methods include:
16/8 Method: This involves a 16-hour voluntary fasting period each day, followed by an 8-hour eating window.
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Alternate-Day Fasting (ADF): This involves voluntary fasting every other day, typically consuming a very low-calorie amount (around 500-600 calories) on fasting days.
5:2 Diet: This involves eating normally for five days of the week and restricting calorie intake to 500-600 calories on the remaining two days.
Potential Advantages of Combining Keto and Intermittent Fasting
Some proponents suggest that combining the keto diet and intermittent fasting can lead to synergistic effects, potentially accelerating weight loss, improving metabolic health, and enhancing energy levels.
Accelerated Ketosis and Fat Loss: The keto diet already promotes ketosis by restricting carbohydrate intake. Intermittent fasting may further accelerate this process by depleting glycogen stores and prompting the body to burn fat for fuel more quickly. As you fast on the keto diet, your body has to use its stores of fat, rather than what you just ate, to fuel itself, which will help you lose even more weight and fat faster than when you eat three times a day on the keto diet. A recent study showed that combining a low-carbohydrate diet and intermittent fasting caused increased weight loss and improved insulin levels, compared to calorie restriction alone.
Enhanced Insulin Sensitivity: Both the keto diet and intermittent fasting have been shown to improve insulin sensitivity, which is crucial for regulating blood sugar levels and reducing the risk of type 2 diabetes. Fasting helps to decrease overall insulin levels, but even keto-approved food (the small number of carbs and the protein) will cause a slight increase in insulin levels after you eat. Fasting does away with that because food is what triggers insulin levels to rise. When you fast, you increase your sensitivity to insulin, those hormone levels drop, and you’re less likely to do what high insulin tells your body to do: Burn glucose and store fat. When carbs (and, therefore, insulin to a large degree) is out of the picture, as is the case with fasting, your body can burn fat, rather than store it.
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Improved Metabolic Health: Combining these strategies may lead to improvements in various metabolic markers, such as cholesterol levels, blood pressure, and blood sugar control. Alternate day fasting (ADF) is a popular weight loss regimen. Whether carbohydrate restriction can enhance the weight loss achieved with ADF remains unclear. Adults with obesity (n = 31) participated in ADF (600 kcal “fast day” alternated with an ad libitum “feast day”) with a low‐carbohydrate background diet (30% carbohydrates, 35% protein, and 35% fat). Findings suggest that ADF combined with a low‐carbohydrate diet is effective for weight loss, weight maintenance, and improving certain metabolic disease risk factors such as LDL cholesterol, blood pressure, and fasting insulin.
Increased Autophagy: Fasting is known to stimulate autophagy, a cellular process that removes damaged or dysfunctional cells, promoting cellular repair and regeneration. Eating a keto diet, you’re providing fat for your body to burn, and it will burn fat from food before it turns to stored body fat. When you burn through the food you’ve eaten, however, your digestive system begins to work off of stored fat. The longer your fasting period lasts, the more time you’re giving yourself to work through stored fat.
Potential for Muscle Preservation: Despite concerns about muscle loss during fasting, some studies suggest that intermittent fasting, particularly when combined with a high-protein diet, may help preserve muscle mass. Fasting not only affects insulin and glucose levels, but also exerts a significant effect on a closely related hormone, insulin-like growth factor 1 (IGF-1). IGF-1 is stimulated by HGH and causes most of the adverse effects of excess HGH, like high blood sugar and the risk of cancers. IGF-1 is mostly made by the liver and helps promote the growth of almost all the cells in both children and adults, from muscles to bones.
Potential Risks and Considerations
While the combination of keto and intermittent fasting may offer potential benefits, it's crucial to be aware of the potential risks and considerations:
Nutrient Deficiencies: The keto diet, particularly when combined with the restrictive nature of intermittent fasting, can increase the risk of nutrient deficiencies if not carefully planned. “Because the keto diet is so restricted, you’re not receiving the nutrients - vitamins, minerals, fibers - that you get from fresh fruits, legumes, vegetables and whole grains,” says Dr. Ring.
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Electrolyte Imbalance: Both the keto diet and fasting can lead to electrolyte imbalances, such as low sodium, potassium, and magnesium. This can result in symptoms like fatigue, muscle cramps, and headaches. When you’re fasting, you lose electrolytes, such as potassium and sodium, at higher rates. Replenishing these lost electrolytes could prevent the weakness, fatigue, headaches, and other symptoms that sometimes manifest.
The "Keto Flu": The initial transition to a ketogenic diet can cause flu-like symptoms, often referred to as the "keto flu." These symptoms can include headaches, fatigue, brain fog, and irritability.
Gallbladder Issues: The high-fat content of the keto diet can potentially exacerbate gallbladder problems in individuals with pre-existing conditions.
Sustainability and Adherence: Both the keto diet and intermittent fasting require significant lifestyle adjustments and can be challenging to maintain long-term. Because of the stringent food restrictions, many find the keto diet hard to stick to.
Individual Variability: The response to the keto diet and intermittent fasting can vary significantly from person to person. Factors such as genetics, activity level, and underlying health conditions can influence the outcomes.
Blood Pressure and Blood Sugar Drops: The keto diet can cause your blood pressure to drop in the short term due to a reduction in blood volume and changes in your fluid balance. Symptoms of low blood pressure include dizziness, lightheadedness or fainting, especially when standing up quickly. Following a keto diet can also cause your blood sugar to drop, which can be dangerous for people living with diabetes. Common symptoms of low blood sugar include weakness or shaking, sweating, a fast heartbeat and dizziness.
Practical Tips for Combining Keto and Intermittent Fasting
If you're considering combining the keto diet and intermittent fasting, here are some practical tips to help you do it safely and effectively:
Consult a Healthcare Professional: Before making any significant dietary changes, it's essential to consult with a healthcare professional or a registered dietitian. They can assess your individual needs, identify any potential risks, and provide personalized guidance.
Start Slowly: Avoid making drastic changes all at once. Gradually transition into the keto diet and slowly introduce intermittent fasting. This will give your body time to adapt and minimize potential side effects.
Prioritize Nutrient-Dense Foods: Focus on consuming nutrient-dense, whole foods during your eating windows. This will help ensure that you're meeting your vitamin and mineral needs.
Stay Hydrated: Drink plenty of water throughout the day, especially during fasting periods.
Supplement Wisely: Consider supplementing with electrolytes, such as sodium, potassium, and magnesium, to prevent imbalances.
Listen to Your Body: Pay attention to how your body is responding and adjust your approach as needed. If you experience any adverse symptoms, such as excessive fatigue, dizziness, or muscle cramps, consult with your healthcare provider.
Consider a "Fat Fast" for Stalled Weight Loss: The fat fast is a technique brought by Dr. Atkins’ New Diet Revolution - used by people who are metabolically resistant and have trouble with their induction. It is important to stress that a fat fast should only be followed for a few days maximum as it does not provide sufficient protein and other nutrients. To be clear: You should not fat fast consistently.
Consider Keto Coffee: Keto Coffee can be made via a variety of methods. Traditionally, it’s made using part grass-fed butter and part unrefined coconut oil. The amounts of each that you use entirely depend on your hunger level and how new you are to this variety of Intermittent Fasting. Not feeling hungry is VERY important for achieving your wellness goals.
The Importance of a Balanced Perspective
While the combination of keto and intermittent fasting may offer potential benefits for some individuals, it's crucial to approach this strategy with a balanced perspective. It's not a magic bullet for weight loss or a one-size-fits-all solution. Individual results may vary, and it's essential to prioritize overall health and well-being over rapid weight loss.
For long-term weight loss, Dr. Ring, Dr. Cheema advocates making small changes based on your health goals. “People tend to burn out on those big goals and challenges, and then they go back into their own habits,” he explains. “Just because you were super fit between the ages of 36 and 38 may not extend your healthy life. But if you make small changes consistently every day from ages 36 to 66, that probably will have a big impact. No one diet fits all, and what works for one person may not work for another.