Intermittent Fasting Fads vs. Reality: A Q&A with Karen Bain, RDN, LD

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Before beginning any new dieting or exercise regimen, please consult a medical professional.

Despite being an age-old concept practiced as part of major religious holidays such as Ash Wednesday, Ramadan and Yom Kippur, intermittent fasting (IF) has resurfaced as the health and fitness industry's latest craze.

According to Karen Bain, RDN, LD, a clinical dietitian with UNR Med's Endocrinology, Wellness and Weight Management Clinic, intermittent fasting "is a method of practice where one eats normally some days and little to nothing on other days." Among IF methods and regimens are the 5:2 diet that consists of five days of normal eating and two days of fasting, a 24-hour fast one to two times per week, alternate-day fasting, randomly skipped meals one to two times a week, five-day-per-month fasting, and the popular Bulletproof Intermittent Fasting trend, especially embraced by CrossFitters.

The question remains: is intermittent fasting a healthy form of weight management or simply a dieting trend with more health risks than rewards? The short answer: both.

Bain explains, "Most IF research involves animals, so there are still many unknowns for long-term practice. However, the cited health benefits include reduction in obesity, maintained muscle mass, decreased fat mass, preserved learning and memory, extended longevity, increased adiponectin-a protein that plays a role in metabolizing carbohydrates and fat-reduction in inflammatory markers and prevention or slowed progression of diseases, such as diabetes and cancer."

While this list of positives seems substantial, Bain warns that an IF regimen needs to be approached with caution and discipline:

"Intermittent fasting does not teach important aspects of overall healthy eating and lifestyle management. Overeating unhealthy foods on 'feed' days may override the benefits. IF can be subjective and practiced in extreme measures, which can lead to unwanted side effects such as dehydration or other imbalance of nutrients."

Intermittent fasting methods that combine increased caffeine intake and high intensity exercise combined with limited caloric intake, such as Bulletproof Intermittent Fasting, may be included in these extreme measures. Followers of this latest fasting trend are told they will see better physical results while maintaining, even boosting, mental performance. Bain explains how, in her opinion, this form of IF is more a fad than a sustainable lifestyle:

"Caffeine is a metabolism booster, but the effects are temporary with a dependence/withdrawal response over time that cannot be remedied by simply consuming more of it. Drinking caffeine will produce an artificial metabolic demand while performing high-intensity workouts, thus increasing the calorie and fat burn. Caffeine stimulants may increase anxiety, blood pressure and cause sleep issues. In light of intermittent fasting, this is an additional stressor. The bottom line becomes, how can you increase fat burn without depending on manufactured stimulants? That's a whole topic in itself, but research shows using a sustainable approach to increase lean muscle mass without stimulants may have greater benefit and be less harmful in the long run."

So, what is a more sustainable method? Although there is no simple answer to this question, Bain provides some insight on effective intermittent fasting:

"Intermittent fasting can ignite 'healthy stress' to a person's metabolism that may initiate weight loss momentum. However, one size does not fit all. Metabolism is individual, and what works for one may not work for another. If a person has a history of yo-yo dieting and has been unsuccessful managing their weight, it would benefit them to seek input from a registered dietitian who can assess and evaluate their reasons for not reaching their weight loss goals and develop a lifestyle program that can bring lasting change and optimal health. It's also important to note that IF is not recommended for certain individuals including pregnant or breastfeeding mothers, children and teens and people recovering from surgery or illness."

Bain's final advice?

"Consult a health professional to ensure you are well informed and educated about this practice and how it will affect you individually. Once you have lost weight on IF and start eating normally again, it is easy to gain the weight back. Make sure to work with your physician or registered dietitian to determine the best balance of fasting, feeding and physical activity."

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The University of Nevada, Reno School of Medicine is a community-based, research-intensive medical school with a statewide vision that has served Nevada for 50 years. The state's first public medical school, UNR Med fosters a healthy Nevada through excellence in medical education, medical care, research and community engagement, within a culture of respect, compassion and inclusion. Through targeted growth and investment in research, clinical services, education and outreach, UNR Med is improving the future of health care. For more information, visit our 50th anniversary website.