What’s the deal with intermittent fasting?

By Nicole Houghtaling, RD, Pn1

Posted on Thursday, January 10, 2019


Q: I’ve been hearing a lot about intermittent fasting. What are the benefits and is this something I should try? Thomas

A: Dear Thomas: There has definitely been a lot of buzz around the topic of intermittent fasting, making it one of the newer fad diets out there. Intermittent fasting (IF) is essentially a diet that cycles between periods of eating and not eating and is often promoted for weight loss. There are several variations though so it’s important to know the different types and what type we’re talking about.

To give you an idea, here’s a quick overview on some of the common variations.

Intermittent energy restriction (IER): Periods of energy restriction interspersed with normal energy intake.

Alternate day fasting (ADR): “Fasting days” in which no energy-containing food or beverages are consumed, alternating with days where food and beverages are consumed as desired.

Alternate day energy restriction (ADER): Energy restriction of 60 -70 per cent below estimated requirements, or a total fast on alternate days.

Modified fasting regimens: Consumption of 20 - 25 per cent of energy needs on regularly scheduled “fasting” days.

Time restricted feeding (TRF - A.K.A 16:8 diet): Consuming energy intake as desired within specific time windows (from 10 a.m. to 6 p.m., for example), which induces fasting periods on a routine basis.

Religious fasting: Fasting regimens undertaken for religious or spiritual purposes.

What does the research say? Intermittent energy restriction may promote weight loss however, it is no more effective than continuous energy restriction (CER). Continuous energy restriction means consistently limiting your calories.

Did you know that when you lose weight, you lose fat and muscle? Studies suggest the overall protein content, rather than the pattern of energy restriction (like intermittent energy restriction vs. continuous energy restriction), is what determines how much fat free mass (muscle) you lose. In other words, you need to make sure you are getting adequate protein to help preserve your muscle mass when you lose weight. IF is counterproductive if you are trying to put on significant muscle mass.

It may be challenging to follow specific intermittent fasting diet patterns over time as studies have shown it is difficult to maintain daily living activities, likely due to common side effects including: fatigue, stress, headaches, constipation, dehydration, mood variations and confusion.
Currently there is a lack of evidence regarding the impact of intermittent fasting on health behaviours such as diet, sleep and physical activity. Long-term quality studies are still needed to examine weight maintenance after weight loss and short and long-term quality studies are needed, especially in military populations, to assess the effects of intermittent energy restriction on specific military environmental factors.

So what’s the bottom line? At present there is insufficient evidence to recommend any intermittent energy restriction regimens. It is not clear if long-term IER is a safe, effective method of weight control for overweight or obese individuals, or if IER provides health benefits to people at any weight regardless of weight loss.

Military personnel should avoid being on duty in a fasted state as it can negatively affect safety and operational readiness.

Already trying intermittent fasting? A healthy balanced diet is still important. Ensure you are meeting your requirements for important nutrients like fibre, vitamins and minerals and stay hydrated. For reasons including performance and injury prevention, avoid fasting while on duty. There’s nothing wrong with weight loss as a goal but remember that your health is more important than a number on the scale. Sleep, stress management, and physical activity, among other factors, all contribute to weight management and a healthy lifestyle.

If you’re looking to learn more about nutrition and/or fad diets, Strengthening the Forces (STF), the CAF’s Health Promotion program, offers quality programs with evidence-based research and skill building.
Contact your local health promotion office and take advantage of what they have to offer. https://www.cafconnection.ca/National/Programs-Services/Health/Health-Promotion-Program.aspx

Nicole Houghtaling is a registered dietitian and is currently completing a Masters in Sports Nutrition. As part of the Strengthening the Forces team she is the Acting Nutrition Wellness Educator and focusses on health promotion nutrition programming for the CAF.

Strengthening the Forces is the Canadian Armed Forces (CAF) healthy lifestyles promotion program providing expert information, skills and tools for promoting and improving CAF members’ health and well-being.