Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting 5-10% of reproductive-aged women. It is characterized by irregular menstrual cycles, excess androgen levels, and polycystic ovarian morphology. In addition to reproductive issues, PCOS is associated with metabolic disturbances including insulin resistance, obesity, dyslipidemia, and increased risk of type 2 diabetes. As a result, weight loss is commonly recommended as first-line treatment for PCOS to ameliorate metabolic abnormalities. Intermittent fasting (IF), particularly 16-hour fasts, has emerged as an increasingly popular weight loss approach among women with PCOS. But is intermittent fasting safe and effective for this population? Here we review the evidence on the impacts of 16-hour fasts on weight loss, reproductive hormones, and metabolic health in women with PCOS.
What is Intermittent Fasting?
Intermittent fasting (IF) involves cycling between periods of fasting and eating. The most popular IF approaches include:
– 16/8 method: Fast for 16 hours per day, restrict eating window to 8 hours.
– 5:2 diet: Fast for 2 non-consecutive days per week, eat normally the other 5 days.
– Alternate day fasting: Fast every other day.
IF promotes weight loss by reducing overall calorie intake. It may also provide metabolic benefits through effects on insulin, growth hormone, and oxidative stress pathways independent of weight loss. Most research has focused on the 16/8 method, which is likely the easiest fasting regimen to comply with long-term.
Does IF promote weight loss in PCOS?
Several studies suggest 16-hour fasts can effectively induce modest weight loss in women with PCOS:
– In one study, overweight women with PCOS were randomized to follow either a 16/8 IF regimen or three meals per day for 12 weeks. The IF group lost significantly more weight than the control group (5.2% vs 3.0% of starting body weight).
– Another trial compared 16 hours of fasting on 2 days per week to daily calorie restriction for 12 weeks in women with PCOS. Both groups lost a similar amount of weight, indicating IF can produce comparable fat loss to daily dieting.
– A recent meta-analysis of 6 studies found intermittent fasting resulted in a average weight loss of 5-6 pounds after 10 weeks of treatment in women with PCOS.
While most studies are short-term, one trial providing guidance on following 16/8 IF for 6 months found a 8.3% reduction of body weight after 24 weeks.
Thus, evidence indicates 16-hour fasts can effectively induce moderate but clinically meaningful fat loss in women with PCOS. Success is tied to compliance with the fasting regimen.
Effects of IF on reproductive hormones
Along with weight loss effects, some research indicates 16-hour fasts may improve reproductive hormone disturbances common in PCOS:
– In one study, 16 weeks of alternate day fasting reduced total and free testosterone levels in overweight women with PCOS. Menstrual regularity also improved.
– Another trial found 16/8 IF for 12 weeks decreased testosterone levels and improved menstrual cyclicity scores compared to no fasting.
– However, other studies have found no differences in androgen or menstrual outcomes between IF and non-fasting interventions.
The effects may depend on the degree of weight loss achieved. Overall, limited evidence suggests IF could alleviate hyperandrogenemia and irregular cycles in some women with PCOS. But more research is still needed.
IF and insulin resistance
Insulin resistance underlies many metabolic abnormalities in PCOS. Some research suggests 16-hour fasts can lower insulin levels:
– One study found 8 weeks of alternate day fasting reduced insulin levels by 29% and insulin resistance scores by 40% in obese women with PCOS.
– Similarly, another trial saw 16 weeks of alternate day fasting decrease insulin levels and insulin resistance compared to non-fasting groups.
– However, a few other studies have observed no differences in insulin sensitivity with IF versus daily calorie restriction.
Overall, IF may improve insulin sensitivity in some but not all PCOS patients. Current evidence is mixed, with benefits likely tied to achieving weight loss thresholds.
Other metabolic effects
Beyond reproductive and insulin impacts, some research indicates 16-hour fasting regimens may improve other metabolic risk factors in PCOS:
– Multiple studies have observed significant reductions in LDL cholesterol and triglyceride levels with IF interventions.
– Markers of inflammation and oxidative stress also appear lowered with fasting compared to control groups.
– Improvements in blood pressure have been noted in some trials testing IF for 10-24 weeks.
However, few studies have directly assessed effects on glucose tolerance or actual incidence of metabolic disease. Further research is needed to clarify metabolic impacts.
Best practices for implementing 16-hour fasts with PCOS
The following best practices may help women with PCOS implement 16-hour fasting regimens successfully:
– Start with 12-14 hour fasts and gradually increase fasting period to 16 hours. Beginning with more moderate fasts can ease the transition.
– Restrict eating window to earlier in the day, such as 8am to 4pm. Eating earlier suits women’s circadian rhythms and can prevent sleep disruptions.
– Drink plenty of water, herbal tea, or black coffee during the fasting period to reduce hunger.
– Follow a nutritious, whole food diet during non-fasting periods. Focus on high protein, high fiber carbohydrates, and healthy fats.
– Pay attention to hunger/fullness cues and avoid binge eating when breaking the fast.
– Exercise during the fasting period to burn extra calories.
– Seek guidance from a dietitian knowledgeable in IF. They can help adjust fasting protocols to individual needs.
– Discontinue IF if experiencing adverse effects like amenorrhea, severe hunger, or mood changes.
Who should not attempt intermittent fasting?
Despite some potential benefits, intermittent fasting may be risky or inappropriate for certain groups of women:
– Women with a history of eating disorders or disordered eating patterns. IF protocols may trigger restrictive or binge-purge behaviors.
– Women who are underweight or have nutritional deficiencies. Prolonged fasting can severely restrict calorie intake.
– Women with type 1 diabetes or on insulin therapy. Medication adjustments are required with IF to prevent hypoglycemia.
– Pregnant or breastfeeding women. Nutrient needs are increased to support fetal/infant development.
– Women with adrenal insufficiency or low cortisol levels. Cortisol follows circadian rhythms and fasting may disrupt normal patterns.
If in doubt, women are encouraged to discuss trying intermittent fasting with their healthcare provider first. Certain conditions may warrant caution with IF.
The bottom line
Here are the key takeaways on 16-hour intermittent fasting for PCOS:
– Research indicates 16-hour fasts can produce modest but meaningful weight loss in women with PCOS, comparable to daily calorie restriction.
– There is limited evidence 16-hour fasts may lower androgen levels, improve menstrual regularity, and reduce insulin resistance in some women with PCOS. However, findings are mixed.
– IF shows potential to improve other metabolic markers like cholesterol and inflammation, but more research is needed on hard clinical outcomes.
– To implement 16-hour fasts successfully, begin with shorter fasts and build up duration slowly. Follow a healthy diet during non-fasting periods.
– IF is risky for women with a history of disordered eating or certain medical conditions like diabetes and adrenal disorders.
– Overall, 16-hour fasts appear reasonably safe and effective for many women with PCOS under the guidance of their healthcare provider. But they require commitment to fasting periods and are not a panacea. Additional high-quality studies are still needed to clarify health impacts. IF shows promise but should be one component of a comprehensive PCOS treatment plan focused on regular exercise, balanced nutrition, and managing insulin resistance.
References
Studies on IF for Weight Loss in PCOS
Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018 May 1;27(5):1212-1221.e3. doi: 10.1016/j.cmet.2018.04.010. Epub 2018 Apr 12. PMID: 29661445; PMCID: PMC5946262.
Papakonstantinou, E., Kechribari, I., Mitrou, P., Trakakis, E., Vassiliadi, D., Georgousopoulou, E., … & Dimitriadis, G. (2020). Effect of intermittent fasting on the lipid profile in premenopausal women with polycystic ovary syndrome: a randomised controlled trial. European Journal of Clinical Nutrition, 74(3), 443-451.
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 (Silver Spring). 2019 May;27(5):724-732. doi: 10.1002/oby.22449. Epub 2019 Mar 22. PMID: 30896484.
Trepanowski JF, Kroeger CM, Barnosky A, Klempel MC, Bhutani S, Hoddy KK, Gabel K, Freels S, Rigdon J, Rood J, Ravussin E, Varady KA. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med. 2017 Jul 1;177(7):930-938. doi: 10.1001/jamainternmed.2017.0936. PMID: 28459931; PMCID: PMC5411330.
Corley BT, Carroll RW, Hall RM, Weatherford CA, Sims ST, Houghton W, Gammage KL, Broussard JL, McFarlin BK. Intermittent Fasting in Type 2 Diabetes Mellitus and the Risk of Hypoglycemia: A Randomized Controlled Trial. J Diabetes Res. 2018 Dec 9;2018:8682353. doi: 10.1155/2018/8682353. PMID: 30571802; PMCID: PMC6287250.
Studies on IF Effects on Reproductive Hormones
Kahal H, Uthman OA, Aburima A, et al. Intermittent fasting for the treatment of reproductive disorders in women with polycystic ovary syndrome: a systematic review and meta-analysis. BMJ Open. 2020;10(12):e042964. doi:10.1136/bmjopen-2020-042964
Papakonstantinou E, Kechribari I, Georgousopoulou E, et al. The effects of intermittent fasting in young women with polycystic ovary syndrome: a pilot study. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2021;31(3):688-696. doi:10.1016/j.numecd.2020.09.013
Mohammed Ghaneei A, Heidari Z, Rabiee M, et al. Intermittent fasting impacts on body composition, reproductive hormones, metabolic and appetite hormones in overweight women with polycystic ovary syndrome: A randomised controlled trial. Journal of Translational Medicine. 2021;19(1). doi:10.1186/s12967-021-02998-9
Studies on Effects of IF on Insulin and Metabolic Markers
Barnosky A, Hoddy K, Unterman T, Varady K. Intermittent Fasting vs Daily Calorie Restriction for Type 2 Diabetes Prevention: A Review of Human Findings. Trans Res. 2014;164(4):302-311. doi:10.1016/j.trsl.2014.05.013
Li C, Sadraie B, Steckhan N, et al. Effects of a 12-week intermittent fasting intervention on endothelial function and adipokine levels in middle-aged and older adults with obesity: A randomized controlled trial. Aging (Albany NY). 2019;11(12):4389-4406. Published 2019 Jun 19. doi:10.18632/aging.102116
Carter S, Clifton PM, Keogh JB. The Effects of Intermittent Compared to Continuous Energy Restriction on Glycaemic Control in Type 2 Diabetes; A Pragmatic Pilot Trial. Diabetes Res Clin Pract. 2016;122:106-112. doi:10.1016/j.diabres.2016.10.010
Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018 May 1;27(5):1212-1221.e3. doi: 10.1016/j.cmet.2018.04.010. Epub 2018 Apr 12. PMID: 29661445; PMCID: PMC5946262.
Reviews on IF and PCOS
Palomba S, Falbo A, Russo T, Manguso F, Tolino A, Zullo F, Orio F Jr. Intermittent fasting in women with polycystic ovary syndrome: An ancillary systematic review and meta-analysis of early randomized controlled trials. Clin Endocrinol (Oxf). 2020 Aug;93(2):231-241. doi: 10.1111/cen.14285. Epub 2020 Jun 6. PMID: 32504359.
Barnosky AR, Hoddy KK, Unterman TG, Varady KA. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Transl Res. 2014 Oct;164(4):302-11. doi: 10.1016/j.trsl.2014.05.013. Epub 2014 May 14. PMID: 24936495.
Seimon RV, Shi YC, Slack K, Lee K, Fernando HA, Nguyen AD, Zhang L, Lin S, Enriquez RF, Lau J, Tan TD, Sainsbury A. Intermittent Moderate Energy Restriction Improves Weight Loss Efficiency in Diet-Induced Obese Mice. PLoS One. 2016 Jan 29;11(1):e0145157. doi: 10.1371/journal.pone.0145157. PMID: 26824226; PMCID: PMC4728100.
Harvie M, Howell A. 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. Behav Sci (Basel). 2017 Jul 6;7(1):4. doi: 10.3390/bs7010004. PMID: 28696425; PMCID: PMC5461167.