By Carla DiGirolamo, MD, PHD
The science of fitness and nutrition is advancing at a rapid pace. Fad diets and supplements are flooding the mainstream and fertility specialists are increasingly asked “Is there a special diet that will increase my chances of getting pregnant?” or “Is there anything else I can do to improve my chances of conceiving?” One dietary strategy that is gaining popularity is the “Keto Diet.”
WHAT IS THE KETO DIET?
The Ketogenic (“Keto”) Diet has been used to treat intractable epilepsy since the 1920s. This nutrition plan is extremely low in carbohydrates, moderate in protein and high in fat. Once a very low carbohydrate status is achieved, the body switches from using glucose for fuel to metabolizing fatty acids into ketone bodies, which replace glucose as the energy source for cells and tissues. Carbohydrate levels are generally <10% of total daily energy (TDE) or, for most individuals, between 20-50g of carbohydrate per day. For perspective, one piece of wheat toast contains ~ 16g of carbohydrate. Calories not consumed as carbohydrate are instead consumed as fat. As a result, insulin levels decrease and serum glucose levels remain stable due to the metabolism of amino acids and glycerol into glucose.
A review of the evidence by Kirkpatrick et. al in a scientific statement from the National Lipid Association (NLA)1 suggests that although the Ketogenic Diet is an effective way to achieve weight loss, there is no significant advantage over other dietary plans that incorporate moderate carbohydrate and lower-fat alternatives. What is important for successful weight loss, however, is adherence to a dietary plan. Achieving a state of ketosis with the Keto Diet can result in the “keto flu” with symptoms of light-headedness, dizziness and fatigue as well as constipation, abdominal pain and nausea in the first 2-3 weeks2, thus making it difficult to stay engaged in the dietary plan.
The Ketogenic Diet should be considered only for a limited duration of 2-6 months to achieve weight loss, followed by reintroduction of healthy carbohydrates and reduction of dietary fat to achieve a steady, more sustainable state of dietary equilibrium. Long term use of ketogenic diets has been associated with an increase in all-cause mortality (death from all causes)3 and may have unfavorable effects on serum lipid levels. For patients with high cholesterol, high blood pressure, diabetes, pancreatitis and kidney disease, this type of dietary plan should only be considered under close medical supervision1.
DOES IT HAVE TO BE KETO TO WORK?
The Ketogenic Diet represents the far end of a spectrum of dietary strategies to achieve weight loss and a healthier lifestyle. Although the Ketogenic Diet can be an effective choice in healthy individuals seeking weight loss over the short term, modified lower carbohydrate diet alternatives may also achieve favorable results and may promote better adherence and sustainability as a lifestyle.
IS KETO SAFE WHILE I'M TRYING TO CONCEIVE?
The Ketogenic Diet can be an effective strategy to achieve short term weight loss to improve conception success and reduce obesity-related pregnancy complications such as gestational diabetes, gestational hypertension (high blood pressure) and fetal macrosomia (large fetus). In patients with clinical obesity (Body mass index >30), ketogenic and low carbohydrate (<45% of total calories) nutrition plans may reduce circulating insulin levels, improve ovulatory function and improve pregnancy rates compared to no dietary intervention4. These plans can be safely used in otherwise healthy individuals for a limited duration before conception with a measured reintroduction of healthy carbohydrates and fat for longer-term weight loss and weight maintenance. Metabolic ketosis should be avoided once pregnant as the safety of the ketotic state in pregnancy has not been well-studied and may be detrimental. Consultation with a nutritionist in early pregnancy is always recommended.
As with any lifestyle change, it is helpful to consult with your primary care and general obstetric and gynecology providers for helpful suggestions and any needed precautions. Every patient has unique health issues and life circumstances and no single nutrition program works for everyone. However the critical element – whether it is a fitness or a nutritional program – is finding a plan that can be adhered to for the long term with the goal of making the “diet” a lifestyle.
- Kirkpatrick CF et al., Journal of Clinical Lipidology (2019) ePUB. Accepted for publication Aug 13, 2019.
- Kossoff, EH; Epilepsia Open. 2018;3(2):175–192.
- Noto H., et al. PLoS One. 2013;8(1):e55030 Erratum: PLoS One 2019 Feb 7;14(2):e0212203.
- McGrice M and Porter J; Nutrients 2017, 9, 204; doi:10.3390/nu9030204
ABOUT THE AUTHOR
Carla M. DiGirolamo, M.D., Ph.D. is a Reproductive Endocrinologist taking new patients at Boston IVF, Waltham, Massachusetts. She is Board Certified in Reproductive Endocrinology and Infertility as well as general Obstetrics and Gynecology. Dr. DiGirolamo is credentialed as a Level 1 CrossFit Trainer, Les Mills certified group fitness instructor and is a member of CrossFit Health, a worldwide organization of physicians who CrossFit created by CrossFit Founder, Greg Glassman in his quest to cure the world of chronic disease. In addition to helping patients build their families, Dr. DiGirolamo’s special interest is in managing the unique reproductive/endocrine challenges of female athletes.