Intermittent fasting (IF) and the ketogenic diet go hand-in-hand. Many keto-dieters practice short-term intermittent fasting (between 12-24 hours) regularly, but sprinkling in a long-term (>24 hours) fast every now-and-then can provide numerous other benefits. Outside of physiological benefits to the gut microbiome, blood glucose/ketone levels, hormone regulation, and body composition, long-term fasting can provide psychological benefits due to the level of discipline it requires. 
While the length of time and what you consume during your fast is important, what you eat to break your fast is arguably just as crucial. Going several days without food will increase insulin sensitivity and reduce digestive enzymes within the stomach. [2,5,8,9] With these two factors in mind, it is important to plan your fast-breaking meal accordingly. Here are a few tips to follow to make sure you are breaking your fast in an optimal fashion:
1. Avoid Carbohydrates
Since your insulin levels have significantly decreased and insulin sensitivity has significantly increased, it’s important to make sure your first meal after a fast is low in carbohydrates/glucose. Consuming sugary, carbohydrate-rich foods will cause a dramatic spike in blood glucose and insulin levels. Instead, try to avoid carbohydrates (especially processed ones) for the first few hours after you end your fast. Stick to mostly proteins and healthy fats to ease your way back into normal eating patterns.
2. Don’t Eat a Large Meal
Even if you are an avid OMAD-er (One Meal A Day), stick to smaller meals (at least for the first few hours) after breaking a long-term fast. Fasting over 24 hours can drastically reduce digestive enzymes that your stomach will need to break down any food you eat. Eating too much too quickly after a long fast can lead to all sorts of gastrointestinal distress including:
- Stomach Pain
3. Continue To Supplement
Make sure you are continuing to drink plenty of water and supplement with electrolytes for the first few hours after breaking your fast. Since you are consuming smaller meals right after your fast, you are likely still not getting in enough of your key vitamins and minerals; so, it’s important to continue supplementation until your meals transition back to normal.
4. Stick To Whole Foods
This is a pretty good rule of thumb for the ketogenic diet as a whole but, it is especially important after a long term fast. Processed foods (especially certain fibers and sugar alcohols) can have a larger and worse impact after fasting. This being said, even some whole foods should ideally be avoided for the first several hours after a fast; nuts, seeds, and raw vegetables may be difficult to digest. Instead, sticky to cooked, non-starchy vegetables, healthy fats/oils, and broths/soups.
What you break your long-term fast with is one of the most important factors to consider when conducting a >24 hour fast. When breaking a fast:
- Starchy vegetables
- Processed carbohydrates
- Nuts & seeds (includes nut butters)
- Bone broth
- Keto-friendly soups
- Leafy greens cooked in healthy fats
- Easy to digest proteins sources with healthy fats
Are you participating in a long-term fast or fasting challenge? Comment and let us know your results and what foods work best for you when breaking a 24-hour+ fast.
- Longo, V. D., & Mattson, M. P. (2014). Fasting: molecular mechanisms and clinical applications. Cell metabolism, 19(2), 181–192. https://doi.org/10.1016/j.cmet.2013.12.008
- Sutton, E. F., Beyl, R., Early, K. S., Cefalu, W. T., Ravussin, E., & Peterson, C. M. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell metabolism, 27(6), 1212–1221.e3. https://doi.org/10.1016/j.cmet.2018.04.010
- Furmli, S., Elmasry, R., Ramos, M., & Fung, J. (2018). Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin. BMJ case reports, 2018, bcr2017221854. https://doi.org/10.1136/bcr-2017-221854
- Casale J, Huecker MR. Fasting. [Updated 2019 Feb 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534877/
- Stockman, M. C., Thomas, D., Burke, J., & Apovian, C. M. (2018). Intermittent Fasting: Is the Wait Worth the Weight?. Current obesity reports, 7(2), 172–185. https://doi.org/10.1007/s13679-018-0308-9
- Harvie, M., & Howell, A. (2017). Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects-A Narrative Review of Human and Animal Evidence. Behavioral sciences (Basel, Switzerland), 7(1), 4. https://doi.org/10.3390/bs7010004
- Matsuyama S, Ohkura S, Iwata K, et al. Food deprivation induces monocarboxylate transporter 2 expression in the brainstem of female rat. J Reprod Dev. 2009;55(3):256–261. doi:10.1262/jrd.20214
- Lee PC, Brooks S, Lebenthal E. Effect of fasting and refeeding on pancreatic enzymes and secretagogue responsiveness in rats. Am J Physiol. 1982;242(3):G215–G221. doi:10.1152/ajpgi.1982.242.3.G215
- Corring T. The adaptation of digestive enzymes to the diet: its physiological significance. Reprod Nutr Dev. 1980;20(4B):1217–1235. doi:10.1051/rnd:19800713
Chelsea Malone works as a researcher in the field of health and performance supplementation. She contributes science-based articles and information to Ketogenic.com. She received her Bachelor of Science in Biomedical Sciences from the University of Central Florida and her Master of Science in Medical Sciences from the University of South Florida. Her specialties are in biochemistry, immunology, and pathophysiology. In her free time, she enjoys cooking, traveling, hiking, and reading.