Keto dieters often incorporate intermittent fasting (IF) for several reasons. Weight loss is one of these reasons. What does the research show about intermittent fasting for weight loss?
Is intermittent fasting an effective weight-loss tool? Does intermittent fasting work synergistically with the ketogenic diet to promote weight loss?
What Does the Research Show about Intermittent Fasting for Weight Loss?
With intermittent fasting, it’s about when you eat, rather than what you eat. Intermittent fasting is an excellent complement to the ketogenic diet that might help fuel your weight loss efforts.
Intermittent fasting involves cycling between fasting and feeding windows. There are different ways to try intermittent fasting, with most focusing on limiting your snacks and meals to a specific time window — usually between 6 and 8 hours in the day. You might try restricting food intake to 8 hours per day and avoiding eating during the remaining 16 hours. Some keto dieters fast for 24 hours once or twice each week, and others also incorporate caloric restriction.
Research shows intermittent fasting might be beneficial for weight loss for numerous reasons, such as:
- Typically leads to a reduction in caloric intake
- Might increase levels of norepinephrine that can boost metabolism and increase calorie burning 
- Reduces insulin levels that can boost fat burning and promote weight loss
- Improves insulin sensitivity [2,3]
- Might help your body retain muscle mass more effectively than calorie restriction alone 
One review showed that over 3-12 weeks, intermittent fasting can decrease body fat by up to 16% and reduce body weight by up to 8%. The research on intermittent fasting and weight loss is promising. IF might lead to weight loss because caloric intake tends to be reduced by around 25%. Experts believe keto, caloric restriction, and IF can be useful weight loss tools when implemented safely and properly [5,6,7,8,9,10,11].
IF can support blood sugar control, decrease blood sugar levels, and reduce inflammation, which might help you lose weight. Some studies also show IF might naturally heighten levels of human growth hormone (HGH), which can improve body composition and metabolism [12,13,14,15,16].
IF is generally safe and effective, but it might not be suitable for everyone. Some research also points to differences in men and women and potential adverse effects in some women, such as abnormal menstrual cycles. If you have a chronic illness or another medical condition, it’s best to discuss intermittent fasting with your doctor or healthcare professional before jumping into this new dietary pattern [17,18,19].
The Beneficial Synergy of Keto and Intermittent Fasting for Weight Loss
Ketosis is the metabolic state where your body is primarily burning fat for fuel instead of carbohydrates. IF is efficacious when paired with the ketogenic diet. IF can accelerate ketosis and amplify weight loss. .
Intermittent fasting can help your body enter ketosis faster and help mitigate some of the symptoms of the keto flu, such as headaches and fatigue.
Have You Tried Intermittent Fasting for Weight Loss?
Share your experience with intermittent fasting, the ketogenic diet, and weight loss.
1. Zauner, C., Schneeweiss, B., Kranz, A., Madl, C., Ratheiser, K., Kramer, L., Roth, E., Schneider, B., & Lenz, K. (2000). Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. American Journal of Clinical Nutrition, 71(6), 1511-1515. DOI: 10.1093/ajcn/71.6.1511
2. Heilbronn, L. K., Smith, S. R., Martin, C. K., Anton, S. D., & Ravussin, E. (2005). Alternate-day fasting in nonobese subjects: Effects on both weight, body composition, and energy metabolism. American Journal of Clinical Nutrition, 81(1), 69-73. DOI: 10.1093/ajcn/81.1.69
3. Lopaschuk, G. D. (2016). Fatty acid oxidation and its relation with insulin resistance and associated disorders. Annals of Nutrition & Metabolism, 68(Suppl 3), 15-20. DOI: 10.1159/000448357
4. Varady, K. A. (2011). Intermittent versus daily calorie restriction: Which diet regimen is more effective for weight loss? Obesity Reviews, 12(7), e593-601. DOI: 10.1111/j.1467-789X.2011.00873.x
5. Stockman, M-C., Thomas, D., Burke, J., & Apovian, C. M. (2018). Intermittent fasting: Is the wait worth the weight? Obesity Treatment, 7, 172-185.
6. Klempel, M. C., Kroeger, C. M., Bhutani, S., Trepanowski, J. F., & Varady, K. A. (2012). Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutrition Journal, 11(98),
7. Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease process. Ageing Research Reviews, 39, 46-58. https://doi.org/10.1016/j.arr.2016.10.005
8. Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brun, C., Waller, G., Whittaker, V., Sharp, T., Lean, M., Hankey, C., Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: A systematic review and meta-analysis. JBI Evidence Synthesis, 16(2), 507-547. DOI: 10.11124/JBISRIR-2016-003248
9. Patterson, R. E., & Sears, D. D. (2017). Metabolic effects of intermittent fasting. Annual Review of Nutrition, 37, 371-393. https://doi.org/10.1146/annurev-nutr-071816-064634
10. 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, 7(1), 4. https://doi.org/10.3390/bs7010004
11. Harvie, M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., Cuzick, J., Jebb, S. A., Martin, B., Cutler, R. G., Son, T. G., Maudsley, S., Carlson, O. D., Egan, J. M., Flyvbjerg, A., & Howell, A. (2011). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: A randomized trial in young overweight women. International Journal of Obesity, 35(5), 714-727. DOI: 10.1038/ijo.2010.171
12. Arnason, T. G., Bowen, M. W., & Mansell, K. D. (2017). Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study. World Journal of Diabetes, 8(4), 154-164. DOI: 10.4239/wjd.v8.i4.154
13. Faris, M. A-I., Kacimi, S., Al-Kurd, R. A., Fararjeh, M. A., Bustanji, Y. K., Mohammad, M. K., & Salem, M. L. (2012). Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutrition Research, 32(12), 947-955. DOI: 10.1016/j.nutres.2012.06.021
14. Aksungar, F. B., Topkaya, A. E., & Akyildiz, M. (2007). Interleukin-6, C-reactive protein, and biochemical parameters during prolonged intermittent fasting. Annals of Nutrition & Metabolism, 51(1), 88-95. DOI: 10.1159/000100954
15. Salgin, B., Marcovecchio, M. L., Hill, N., Dunger, D. B., & Frystyk, J. (2012). The effect of prolonged fasting on levels of growth hormone-binding protein and free growth hormone. Growth Hormone & IGF Research, 22(2), 76-81. DOI: 10.1016/j.ghir.2012.02.003
16. Bidlingmaier, M., & Strasburger, C. J. (2010). Growth hormone. Handbook of Experimental Pharmacology, DOI: 10.1007/978-3-540-79088-4_8
17. Heilbronn, L. K., Civitarese, A. E., Bogacka, I., Smith, S. R., Hulver, M., & Ravussin, E. (2005). Glucose tolerance and skeletal muscle gene expression in response to alternate day fasting. Obesity Research, 13(3), 574-581. DOI: 10.1038/oby.2005.61
18. Yavangi, M., Amirzargar, M. A., Amirzargar, N., & Dadashpour, M. (2013). Does Ramadan fasting have any effects on menstrual cycles? Iranian Journal of Reproductive Medicine, 11(2), 145-150.
19. Brecchia, G., Bonanno, A., Galeati, G., Federici, C., Maranesi, M., Gobbetti, A., Zerani, M., & Boiti, C. (2006). Hormonal and metabolic adaptation to fasting: Effects on the hypothalamic-pituitary-ovarian axis and reproductive performance of rabbit does. Domestic Animal Endocrinology, 31(2), 105-122. DOI: 10.1016/j.domaniend.2005.09.006
20. Freire, R. (2020). Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets. Nutrition, 69, 110549. https://doi.org/10.1016/j.nut.2019.07.001
Steph Green is a writer, researcher, and singer/songwriter with a passion for all things wellness. In 2016, after four years of struggling with her own health problems and painful autoimmune disease, Steph developed a life-changing and extensive knowledge of keto, nutrition, and natural medicine. She continues on her healing journey and enjoys helping others along the way.