The ketogenic (keto) diet and intermittent fasting (IF) are popular approaches to weight loss, but combining them requires careful consideration. This article breaks down the potential benefits, risks, and necessary precautions before attempting this dietary strategy.
Understanding Keto and Intermittent Fasting
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The Ketogenic Diet: A low-carbohydrate, high-fat diet designed to shift your body into a metabolic state called ketosis. In ketosis, your body burns fat for fuel instead of carbohydrates. This diet has a history of medical use, initially for treating medication-resistant epilepsy, dating back to the 1920s.
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Intermittent Fasting: This dietary approach involves alternating between periods of eating and fasting within a set timeframe. It’s another strategy often used for weight loss.
Why Combine Keto and Intermittent Fasting?
Both keto and IF can contribute to weight loss independently, making a combined approach seem appealing. Combining the diets aims to amplify the benefits of each by increasing ketone levels—which rise during both keto and fasting—potentially leading to greater weight loss.
A study published in 2024 indicated that both diets significantly reduced body fat, and the combination produced even more significant results. This approach may also interest individuals seeking to lower blood glucose levels, but a consultation with a healthcare professional is essential before starting.
Who Should Exercise Caution with Keto and Intermittent Fasting?
Because both diets significantly impact the body, it’s crucial to consult a doctor before starting either or both. While research is ongoing, especially regarding conditions like diabetes, many studies exclude specific groups to ensure accurate results and minimize potential health risks.
Individuals should avoid or carefully consider this combination diet if they:
- Have diabetes and are taking medications (especially insulin or sulfonylureas)
- Have a liver or pancreatic condition
- Are pregnant or breastfeeding
- Are under 18
- Have a history of disordered eating or are underweight
- Have gallbladder disease or gout
- Have an uncontrolled chronic condition
- Have kidney disease or kidney stones
- Are undergoing cancer treatment
Introducing Intermittent Fasting While on Keto: A Gradual Approach
There’s limited research on the best way to introduce IF to a keto diet. Many experience “keto flu”—nausea, fatigue, headaches, insomnia, and vomiting—as their body adjusts to using fat as fuel. These symptoms may be exacerbated in a fasted state.
Common starting points for IF include:
- 12/12 method: Eating and fasting in 12-hour windows.
- 16/8 method: Restricting eating to an 8-hour window.
Potential Health Benefits
While research on the combined keto-IF diet is limited, early findings suggest:
- Increased ketone levels: This can accelerate weight loss.
- Reduced insulin levels and improved insulin sensitivity: May help regulate blood sugar and offer therapeutic benefits for conditions like type 2 diabetes.
- Decreased inflammation: Ketone bodies, which increase on both diets, are associated with reduced inflammation, potentially benefiting various chronic conditions.
Potential Health Risks and Considerations
Combining keto and IF carries potential risks, as both diets have been linked to health issues. Here’s a breakdown:
- Keto Diet Risks: Studies have shown potential for blood sugar fluctuations and, over time, an increased risk of heart disease.
- Intermittent Fasting Risks: A 2024 study presented at the American Heart Association’s Lifestyle and Cardiometabolic Health Scientific Sessions found a 91% higher risk of cardiovascular death in people who limited their eating to an 8-hour window compared to those eating over 12-16 hours.
- Overlapping Risks: Both diets are not recommended for individuals with diabetes, heart disease, a history of disordered eating, or who are pregnant.
The Takeaway
Combining the ketogenic diet and intermittent fasting is a restrictive dietary strategy that requires caution. Due to a lack of extensive research on the combined approach, it’s difficult to predict its impact on your body, especially if you have underlying health conditions. Always consult with your healthcare team before making significant dietary changes. They can help you determine if this combination diet is right for you.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Meira ID et al. Ketogenic Diet and Epilepsy: What We Know So Far. Frontiers in Neuroscience. January 2019.
- Ketosis. Cleveland Clinic. August 2022.
- Yu P. Study on the influence of ketogenic diet and intermittent fasting on the change of body fat rate. Transactions on Materials Biotechnology and Life Sciences. September 2024.
- Gavidia K et al. Treating Diabetes Utilizing a Low Carbohydrate Ketogenic Diet and Intermittent Fasting Without Significant Weight Loss: A Case Report. Frontiers in Nutrition. June 2021.
- Lichtash C et al. Therapeutic use of intermittent fasting and ketogenic diet as an alternative treatment for type 2 diabetes in a normal weight woman: a 14-month case study. BMJ Case Reports. June 2020.
- Bendridi N et al. Ketone Bodies as Metabolites and Signalling Molecules at the Crossroad between Inflammation and Epigenetic Control of Cardiometabolic Disorders. International Journal of Molecular Sciences. November 2022.
- Masood W et al. Ketogenic Diet. International Journal of Molecular Sciences. June 16, 2023.
Meet Our Experts
Maya Feller, MS, RD, CDN, serves as a medical reviewer and is the founder and lead dietitian at Maya Feller Nutrition.
Jessica Migala is a freelance writer specializing in health, nutrition, fitness, and beauty.
