Ask the Expert: What’s the deal with intermittent fasting?


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By Nicole Houghtaling, RD, Pn1

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 intermittent fasting, making it one of the newer fad diets out there.

Intermittent fasting is essentially a diet that cycles between periods of eating and not eating, and is often promoted for weight loss. There are several variations, so it’s important to know the different types.

  • 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% below estimated requirements, or a total fast on alternate days.
  • Modified fasting regimens: Consumption of 20-25% of energy needs on regularly scheduled “fasting” days.
  • Time restricted feeding (TRF – A.K.A 16:8 diet): Energy intake as desired within specific time windows (for example, from 10 am to 6 pm), 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, which means consistently limiting your calories.

Did you know that when you lose weight, you lose fat and muscle?

Studies suggest that overall protein intake, rather than the pattern of energy restriction, is what determines how much fat-free mass (i.e. 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. Intermittent fasting is counterproductive if you are trying to put on significant muscle mass.

Studies have shown it is difficult to maintain daily living activities with intermittent fasting, likely due to common side-effects including fatigue, stress, headaches, constipation, dehydration, mood variations and confusion.

Long term quality studies are still needed to examine weight maintenance after weight loss, as well as the effects of intermittent fasting in military populations.

So what’s the bottom line?

There is insufficient evidence to recommend any intermittent energy restriction regimens. 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 and 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.

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. Contact your local health promotion office and take advantage of what they have to offer. For more information, visit the CAF Connection website.

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 nutrition programming for the CAF.

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