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[5 min read] Intermittent fasting: what physicians need to know

Fasting is hardly new. People have been fasting for religious reasons — Christians, Jews, and Muslims, among others — for centuries. You’ve likely fasted before without even thinking about it. For example, fasting is often required for blood tests, medical procedures, or surgery.

In recent years, intermittent fasting (or IF) has become a popular weight loss technique, at least for some. But what is it, and what does the research say?

For further information on this topic, you may be interested to learn more about the HealthCert Professional Diploma program in Medical Nutrition Management.

What is intermittent fasting?

Intermittent fasting is an eating style in which you eat within a specific time period and fast the rest of the time. In other words, while many diets focus on what you eat, intermittent fasting is all about when you eat.

Intermittent fasting is thought to work by resetting the body’s metabolic system, a process which occurs in the liver when the body’s source of energy shifts from glucose utilisation to free fatty acids and ketones (1). It is promoted to change body composition through loss of fat mass and weight, and to improve markers of health that are associated with disease such as blood pressure and cholesterol levels.

There are a few different approaches to intermittent fasting (2):

  • Time-restricted feeding — Having all your meals during an 8–12-hour window each day, drinking only water the rest of the day.
  • Alternate day fasting — Eating normally one day but only a minimal amount of calories the next; alternating between “feast” days and “fast” days.
  • 5:2 eating pattern — Consuming meals regularly for five days per week, then restricting to no more than 600 calories per day for the other two. This happens by eating very little and drinking only water on those two fasting days.
  • Periodic fasting — Caloric intake is restricted for several consecutive days and unrestricted on all other days. For example, fasting for five straight days per month.

What are the benefits of intermittent fasting?

Weight loss and decreased fat mass remain the most popular reasons for intermittently fasting (3), the effects of which can easily be measured. Researchers report that intermittent fasting may improve body composition, metabolic risk factors, insulin resistance, and weight loss in patients with excess body weight (4). Additionally, intermittent fasting was found to reduce the risk of chronic disease and promote healthier ageing, improvements in insulin sensitivity, and blood glucose stability (5).

However, many people struggle with intermittent fasting in the long term, and some should steer clear, including women who are pregnant or breastfeeding, and those with a history of eating disorders.

Primary care physicians should educate themselves and their patients on the several forms and strategies that intermittent fasting can take to ensure a safe transition.

Learn more about intermittent fasting how it can be incorporated into your practice with the online HealthCert Professional Diploma program in Medical Nutrition Management.

– Lynette Law, Accredited Practising Dietitian

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  1. Stockman M-C, Thomas D, Burke J, Apovian CM. Intermittent Fasting: Is the Wait Worth the Weight? Curr Obes Rep. 2018;7(2):172-85.
  2. Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 2017;37(1):371-93.
  3. Davis CS, Clarke RE, Coulter SN, Rounsefell KN, Walker RE, Rauch CE, et al. Intermittent energy restriction and weight loss: a systematic review. European Journal of Clinical Nutrition. 2016;70(3):292-9.
  4. Patikorn C, Roubal K, Veettil SK, Chandran V, Pham T, Lee YY, et al. Intermittent Fasting and Obesity-Related Health Outcomes: An Umbrella Review of Meta-analyses of Randomized Clinical Trials. JAMA Network Open. 2021;4(12):e2139558-e.
  5. Albosta M, Bakke J. Intermittent fasting: is there a role in the treatment of diabetes? A review of the literature and guide for primary care physicians. Clin Diabetes Endocrinol. 2021;7(1):3.

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