Intermittent Fasting: The Pros & Cons
Intermittent fasting is a widely popular diet craze that has been a staple in the research and diet industry for a few years now. Multiple research studies tout the benefits of intermittent fasting including reductions in insulin resistance, improvements in body composition and increases in markers of longevity. It is easy to broadly recommend intermittent fasting as a preferred way of eating but while the benefits are easy to see, it does have a few potential drawbacks that we should all keep in mind when discussing fasting with clients.
Intermittent fasting or, IMF, is accomplished by creating an abbreviated eating window so the body goes into a fasted state and remains there for at least 16 hours. The popular IMF model called the 16:8 method (fasting for 16 hours and eating within an 8 hour time frame) is probably the most commonly used. Another method of IMF is called the 5:2 plan where one limits their caloric intake to less than 500kcals two days per week and then eats normally the other five days. Both techniques “mimic” fasting in the body without actually having to go the entire day without eating, though some people prefer to just fast for 24 straight hours once a month.
The benefits of fasting, or fasting mimicking diets, has been known for decades and was used to treat a host of both mental and physical ailments. The recent research is focused around using IMF as a tool to increase longevity and vitality by allowing for more effective cell turnover, keeping digestion and the gut biome balanced and reducing insulin resistance which increases risk for diabetes, heart disease and a host of different cancers.
IMF also shows a reduction in body fat but only if the person creates a caloric deficit with the IMF protocol. If the calories in a person’s diet stays the same, but they just shorten their eating window, the person will not lose much weight but can potentially gain the other benefits stated above.
The PROS
In my opinion the biggest advantage to IMF is teaching people behavior change. I have used eating windows to help people avoid eating after dinner/ snacking late at night and also allowing them to get used to learning what hunger actually feels like and making better decisions in response to it. The only reason people lose weight with IMF is due to the calorie deficit created from eliminating meals/ snacks. Limiting food consumption to 8 hours (or less in some cases) each day does have some other benefits including reducing glucose levels and allowing the body to become more insulin sensitive.
The CONS
Most adults can use intermittent fasting as a tool for improving various health factors however IMF is never appropriate for kids, teens or any style of youth or collegiate athletes. I would also not recommend IMF for anyone who needs to build muscle or recover from surgery since you need a calorie surplus to build muscle and soft tissue. It is VERY challenging to create a calorie surplus within an 8-10 hour eating window. One also should consider the amount of protein they need to consume to adequately recover from their exercise routine and ensure they can still meet that amount with a restricted amount of time to eat. This is the biggest downfall I see in intermittent fasting especially since our protein needs are critical to athletic performance, recovery from exercise, immune support, enzyme and hormone production and many other functions. Insulin dependent diabetics must also avoid IMF since it may cause hypoglycemia which can lead to a wide variety of symptoms including coma or death.
Anecdotally, the biggest issue I have seen with my clients who do IMF is the ability to sustain it long term. Not many people can skip breakfast or dinner for the rest of their lives and even if they can, the body will eventually adapt to the stimulus and continued progressions towards body composition goals will be challenges. Again, IMF will not create weight loss without a caloric deficit being created and sustained.
Final Thoughts
I recommend people to try IMF for no longer than about three months and if they still have weight to lose, I transition them into tracking and calorie counting so we can sustain their current calorie deficit but redistribute the calories to assist with sustaining the behaviors created.
I hope this helps you get a better understanding of intermittent fasting and the benefits and drawbacks of this technique. I am always available for questions and would love to assist in furthering your understanding of all things diet and nutrition!
-In Health & Happiness, Jessica Murgueytio
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