February 27, 2018
3 min read

Intermittent fasting: What PCPs need to know

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Fatima Cody Stanford
Fatima Cody Stanford

As the obesity epidemic looms over the United States, numerous weight loss trends have surfaced. One of the latest fads includes intermittent fasting, a cycle of alternating between periods of calorie restriction and periods of normal eating.

Although there is limited research on the clinical effects of intermittent fasting, some studies suggest that the regimen protects against coronary heart disease and aids in weight loss.

One study, published in Nutrition and Metabolism, revealed that intermittent fasting with a liquid diet reduces body weight and risk of heart disease. In addition, two systematic reviews, published in Molecular and Cellular Endocrinology and Nutrients, showed that although intermittent fasting was effective for weight loss, it was not superior to continuous dieting.

Additionally, a study published in JAMA Internal Medicine found that intermittent fasting was not significantly more effective for weight loss, weight maintenance or improvement in cardiometabolic health indicators, including BP, blood glucose and insulin resistance, than restricting daily calorie intake.

In practice, while benefits have been shown, successfully adopting intermittent fasting may be difficult for many patients, Fatima Cody Stanford, MD, MPH, MPA, instructor of medicine and pediatrics at the Harvard Weight Center at Harvard Medical School, told Healio Internal Medicine.

“Intermittent fasting has been linked to longevity and improved health,” Stanford said. “However, many people do struggle with being able to commit to a long-term intermittent fasting. In some people who choose to intermittently fast, there is binge eating as a compensation for the caloric deficit associated with intermittent fasting.”

Primary care physicians should educate themselves and their patients on the several forms and strategies that intermittent fasting can take on, she said.

“For example, there is alternate day fasting, whereby a person eats normally for 24 hours, which is followed by a restriction of calories to approximately 500 calories a day on alternating days,” she said. “Some persons choose to intermittent fast by eating all of their calories between 8 a.m. and 2 p.m. daily.”

Intermittent fasting has not been proven to play a significant role in decreasing obesity rates, according to Stanford.

“However, some patients have finally found this to be a viable tool for managing some excess weight,” she said.

To ensure a safe transition to this type of diet, patients should seek assistance and consider their overall health before making any decisions.

“Intermittent fasting can be done safely, but often persons need the guidance of a dietitian or obesity medicine physician at the start,” she added. “If done in conjunction with professional guidance, there should not be a risk of nutrient deficiencies.”


Use of intermittent fasting should be carried out with caution in patients with diabetes or other medical conditions where fasting might lead to low blood sugar, Stanford said.

As opposed to using intermittent fasting as a first-line therapy for obesity, primary care physicians should emphasize lifestyle as the first approach to achieving a healthy weight, she said. A high-quality diet consisting of whole grains, lean protein, vegetables and fruits, as well as a robust physical activity regimen with a minimum of 150 minutes of moderate intensity physical activity on a weekly basis should be recommended to all patients, she said.

Physicians should recommend that patients get adequate restful sleep and make efforts to reduce and minimize their stress in addition to diet and physical activity, according to Stanford.

“If these efforts do not help people achieve a healthy weight, the addition of the comprehensive weight management center where the patient can undergo work with an obesity medicine physician, psychologist, and/or dietitian is beneficial,” Stanford said. “Some patients will need the addition of weight loss medications and or surgery to help them achieve a healthy weight.”

New weight loss fads are always emerging and keeping up with the trends can be difficult, she said. Patients are often the best source of education of weight loss fads, according to Stanford. – by Alaina Tedesco


Headland M, et al. Nutrients. 2016;doi:10.3390/nu8060354.

Kroeger CM, et al. Nutr Metab (Lond). 2012;doi:10.1186/1743-7075-9-98.

Seimon RV, et al. Mol Cell Endocrinol. 2017;doi:10.1016/j.mce.2015.09.014.

Trepanowski JF, et al. JAMA Intern Med. 2017;doi:10.1001/jamainternmed.2017.0936.

Disclosure: Stanford reports no relevant financial disclosures.