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Keto and Intermittent Fasting

Keto and intermittent fasting are two diet that can combined. Find out what benefits you could get by doing so.
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May 29, 2021
Summary

Combining intermittent fasting and keto can be an effective strategy to accelerate your weight loss.

Some people who do this love it but that doesn’t mean it’s the best diet for you. If you’re curious, try it out and see how you feel. You can always stop and just try keto or just try intermittent fasting and see if you prefer doing just one. 

What’s important is doing what makes you feel best so feel free to experiment!

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

Both intermittent fasting and the ketogenic diet, also known as “keto”, are two of the most popular health trends. Many people are turning to one or both of these diets to lose some weight and improve their overall health.


There is research that substantiates the health improvements associated with these two diets, but many are wondering if it is a safe and effective strategy to incorporate both. 

What Is Keto?


The ketogenic diet is a very high-fat, moderate protein, and very low-carbohydrate diet. Most people on keto eat about 20-50 grams of carbs each day(1,2). Decreasing the daily consumption of carbs forces the body to rely on stored fat for energy instead of stored glucose.


When your body breaks down fat for energy, it creates products called ketones and the entire process is called ketosis. These ketones are able to be used by the body and brain as energy for all bodily functions(2,3).


The keto diet is popular because of its ability to allow people to lose weight, improve insulin resistance, better cognitive ability, and more.

What is Intermittent Fasting?

Intermittent fasting is a dietary pattern where individuals will incorporate longer bouts of fasting into their daily routine. While we all typically fast for about 8 hours when we are asleep, Intermittent fasting patterns require people to fast for longer. 


There are many different types of fasting such as alternate day fasting, one meal a day, and fasting for one or two days a week. The most popular form is probably the 16/8 where individuals fast for 16 hours of the day and eat freely for the remaining eight.


Studies have shown that intermittent fasting can help people lose weight, lower their risk for cardiovascular disease, improve glucose tolerance, and reduce inflammation(4–7).

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Keto and Intermittent Fasting

There are many people who claim to be doing keto while intermittent fasting and love it. Maybe you have friends who are doing this or maybe you’ve seen it on social media; either way, success stories about incorporating both diets are everywhere. That’s because both diets operate very similarly so when done together, you may be able to see results faster.

Incorporating both diets at the same time may make the transition into intermittent fasting easier. When fasting, your body’s glucose supply starts to decrease so your body will start using your body fat for energy, which is the premise of the keto diet. This may help you feel less tired, irritable, and hungry.

Because your body starts to focus on burning fat, this also changes your body’s glucose metabolism. You will see a decrease in insulin and blood glucose levels, which is how both diets can help people improve their glucose tolerance.

Faster Weight Loss

Because both of these diets help “train” your body to burn more fat, you can expect to see faster weight loss. 

Both of these diets not only push your body to burn more fat for energy, they do it in ways that help the body maintain its fat-burning potential even if you were to go back to a normal eating pattern. 

Studies have shown that both diets help increase the mitochondrial density in your fat stores. This is basically a fancy way of saying that your body’s fat will contain a different amount of compounds you naturally find in the cells. This in turn, increases thermogenesis, or the amount of heat your body produces. The more heat your body produces, the more calories you burn(8–10).

Faster Health Benefits

Both of these diets cause similar health improvements. While there haven’t been any studies on combining intermittent fasting and keto, you may have faster improvements in different markers related to overall health. Both diets help people improve their blood glucose levels, insulin resistance, inflammation and some cardiovascular risks so you may see faster improvements with for those with these types of metabolic conditions(2,6,11–18).

What Should You Do?

After reading this article, you may want to jump right into a keto intermittent fasting dietary pattern. But you’ll have to keep in mind some of the potential downfalls to this diet.

For starters, there aren't any studies that have investigated keto with intermittent fasting. Everything about combining them sounds fantastic but this hasn’t been tested yet. There could be some drawbacks scientists aren’t aware of.

Many people find keto very hard. Doing intermittent fasting at the same time should help with the transition but it may still be too difficult for you to do. If that’s the case, that’s ok! Humans are unique and there isn’t a perfect diet for everyone. If you decide to try keto and intermittent fasting and decide you can’t live without bread, then maybe just intermittent fasting is right for you. 

There is also the “keto flu” many people report when first starting out on a keto diet. This is when people report being extremely lethargic, very irritable, while having trouble thinking and focusing(19). This tends to happen because your body needs to adapt to burning so much fat for energy so you’re not in any physical danger, but you might be uncomfortable. While these symptoms tend to go away after about 2 weeks, you might find them unbearable. Just listen to your body and remember to do what is best for you.

Lastly, people on keto diets eat more fat (that’s the premise of keto) but they often will eat significantly more saturated fat. If you are someone who is at risk of certain metabolic diseases such as cardiovascular disease, high blood pressure, or diabetes, you should speak with a physician before trying keto just to be safe.

Trying It Out

If you’ve decided you still want to try keto and intermittent fasting, then give it a shot and see if you like it! You can also try starting one and waiting until you adjust before incorporating the other; you don’t need to start both at once, but it’s entirely up to you. 

You can also try combining both diets at the same time for a few weeks or a few months. This would be enough time for you to lose some weight, get some of the health benefits, and for your body to be better adapted to burning more fat long-term. After that, you can pick one of the diets to maintain or go back to a normal eating pattern.

Keto and Intermittent Fasting Typical Day

If you’re thinking about combining keto and intermittent fasting, it may seem a little overwhelming trying to figure out how to start. We’ve provided an example of what a typical day might look like if you’re following a 16/8 diet plan.

6:00am: Water, tea, or black coffee (coffee will NOT break your fast(20))

8:00am: Water, tea, or black coffee

11:00am: You’ve completed your fast! Eat a keto-friendly breakfast such as an omelet with smoked salmon, cheese, and spinach. 

2:00pm: For lunch, you could have a green salad with some grilled chicken, nuts and seeds, cheese, avocado, and some extra veggies!

7:00pm: For dinner, you could have about 8oz of any meat (steak, chicken, or fish) with some sautéed or grilled veggies like brussels sprouts or broccoli. 

This is just an example of a diet plan when combining keto and a 16/8 intermittent fasting diet pattern. You can adjust the window of eating to accommodate your schedule and preferences. 

Also, feel free to snack throughout the day if you’re hungry. Some keto-friendly snacks include nuts or nut butter, seeds, bullet-proof coffee (coffee with coconut oil and/or butter), hard-boiled eggs, raw veggie sticks, and string cheese.

Keto is very popular so there are so many recipes out there. If you plan on trying intermittent fasting with keto, it can seem restrictive at first so try planning out your first week by finding some recipes and buying the ingredients ahead of time – it’ll make the transition easier.

References:

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2. Dhamija R, Eckert S, Wirrell E. Ketogenic diet. Can J Neurol Sci [Internet]. Canadian Journal of Neurological Sciences; 2013 [cited 2021 May 17];40:158–67. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499830/

3. Paoli A. Ketogenic diet for obesity: Friend or foe? [Internet]. International Journal of Environmental Research and Public Health. Multidisciplinary Digital Publishing Institute  (MDPI); 2014 [cited 2021 May 17]. p. 2092–107. Available from: /pmc/articles/PMC3945587/

4. Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. BioMed Central Ltd.; 2016;14. 

5. Sandoval C, Santibañez S, Villagrán F. Effectiveness of intermittent fasting to potentiate weight loss or muscle gains in humans younger than 60 years old: a systematic review. Int J Food Sci Nutr [Internet]. Taylor and Francis Ltd.; 2020 [cited 2021 May 10]; Available from: https://pubmed.ncbi.nlm.nih.gov/33397167/

6. Antoni R, Johnston KL, Collins AL, Robertson MD. Effects of intermittent fasting on glucose and lipid metabolism. Proceedings of the Nutrition Society [Internet]. Cambridge University Press; 2017 [cited 2021 May 10]. p. 361–8. Available from: https://pubmed.ncbi.nlm.nih.gov/28091348/

7. Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG, Leeuwenburgh C, Mattson MP. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity. Blackwell Publishing Inc.; 2018. p. 254–68. 

8. Muralidhara D V., Desautels M. Changes in brown adipose tissue composition during fasting and refeeding of diet-induced obese mice. Am J Physiol - Regul Integr Comp Physiol. Am J Physiol; 1994;266. 

9. Saito M. Brown adipose tissue as a regulator of energy expenditure and body fat in humans. Diabetes and Metabolism Journal. Korean Diabetes Association; 2013. p. 22–9. 

10. Saito M. Human brown adipose tissue: Regulation and anti-obesity potential. Endocrine Journal. Japan Endocrine Society; 2014. p. 409–16. 

11. Hutchison AT, Regmi P, Manoogian ENC, Fleischer JG, Wittert GA, Panda S, Heilbronn LK. Time‐Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial. Obesity [Internet]. Blackwell Publishing Inc.; 2019 [cited 2020 May 21];27:oby.22449. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1002/oby.22449

12. Jamshed H, Beyl RA, Manna DLD, Yang ES, Ravussin E, Peterson CM. Early time-restricted feeding improves 24-hour glucose levels and affects markers of the circadian clock, aging, and autophagy in humans. Nutrients. MDPI AG; 2019;11. 

13. Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, Pawlak-Osińska K, Wiciński M. Intermittent fasting in cardiovascular disorders—an overview. Nutrients. MDPI AG; 2019. 

14. Longo VD, Mattson MP. Fasting: Molecular mechanisms and clinical applications. Cell Metabolism. NIH Public Access; 2014. p. 181–92. 

15. Paoli A, Tinsley G, Bianco A, Moro T. The influence of meal frequency and timing on health in humans: The role of fasting. Nutrients. MDPI AG; 2019. 

16. Mattson MP, Allison DB, Fontana L, Harvie M, Longo VD, Malaisse WJ, Mosley M, Notterpek L, Ravussin E, Scheer FAJL, et al. Meal frequency and timing in health and disease. Proc Natl Acad Sci U S A [Internet]. National Academy of Sciences; 2014 [cited 2021 May 6];111:16647–53. Available from: /pmc/articles/PMC4250148/

17. Pinto A, Bonucci A, Maggi E, Corsi M, Businaro R. Anti-oxidant and anti-inflammatory activity of ketogenic diet: New perspectives for neuroprotection in alzheimer’s disease [Internet]. Antioxidants. MDPI AG; 2018 [cited 2021 May 17]. Available from: /pmc/articles/PMC5981249/

18. Masino SA, Ruskin DN. Ketogenic diets and pain. Journal of Child Neurology [Internet]. NIH Public Access; 2013 [cited 2021 May 17]. p. 993–1001. Available from: /pmc/articles/PMC4124736/

19. Bostock ECS, Kirkby KC, Taylor B V., Hawrelak JA. Consumer Reports of “Keto Flu” Associated With the Ketogenic Diet. Front Nutr [Internet]. Frontiers Media S.A.; 2020 [cited 2021 May 17];7:20. Available from: /pmc/articles/PMC7082414/

20. Keirns B, Elliott D, Sciarrillo C, Koemel N, Poindexter K, Emerson S. Effect of Black Coffee on Fasting Metabolic Markers and an Abbreviated Fat Tolerance Test. Curr Dev Nutr [Internet]. Oxford University Press (OUP); 2020 [cited 2021 May 18];4:639–639. Available from: /pmc/articles/PMC7258390/?report=abstract

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