Intermittent Fasting Unwound

Intermittent Fasting Unwound

by Vanessa Rissetto, MS RD CDN and Kristin Reisinger MS RD CSSD


Everybody thinks they are an expert in something, and, unfortunately for me, it happens a lot with nutrition. People often try to tell me that they feel prepared to tackle the very complicated science of nutrition by just adding the latest superfood trend they read about in Men's Health or saw on Dr. Oz.  Frankly, life is too short to correct those that aren’t close friends or clients - and I suspect scientists in other fields feel the same way.  But I like talking to people, so recently I found myself chatting away with someone who was telling me all about “Intermittent Fasting.”  

What is Intermittent Fasting, you ask?  Intermittent Fasting (IF) is a relatively new nutritional method based on going long periods of time without eating in order to improve metabolism and your body’s efficacy for utilizing energy.  It is thought that our ancestors have been doing this since the beginnings of man.  It purports various periods of time of fasting (can be a full 24 hour window every 3-5 days, or a system of a daily 8 hour “fed” state followed by a 16 hour “fasting” state often from the hours of 10pm to 2pm the following day).  It is a widespread method of weight loss and improved performance system of nutrition that goes against the grain of the typical “5-6 small meals daily” we usually hear about.  

How does it work?  Well, usually, after you eat, you enter the “fed state,” which lasts for about 3-5 hours while your body digests what you have just eaten. Current thinking is that it is hard to burn fat while you are in the “fed state” because of elevated insulin levels in the body. Remember, insulin is an anabolic hormone that promotes storage, not the burning of calories.  Once the body leaves the “fed state” and your food has been digested, you enter the “post absorptive state,” which continues until about 8-12 hours after your last meal. The final stage is what’s called the “fasted state.” So, what's so great about the “fasted state,” and why am I telling you about it?  

Firstly, during the “fasted state” there is improved insulin sensitivity. As stated before, insulin is an anabolic hormone which helps you absorb nutrients from foods and uses the sugars from the food and directs them to your liver, muscles and fat cells so that they can be used and stored as energy later on. This means that when we eat in excess we are unable to reap the benefits of insulin. By eating less frequently, less insulin is released, and this means that when insulin is released we are much more sensitive to it. This makes it easier to lose fat, improve blood flow to our muscles and, some even believe, limit the effect that an "unhealthy diet" may have on the metabolism. 

Secondly, fasting can simply promote muscle gain and fat loss.  There is some good news here: some studies have shown that training in a “fasted state” is a great way to build lean mass and boost insulin sensitivity; strength training on an empty stomach has been shown to help with fat loss because those that train in a “fasted state” become better at burning fat due to an increase in fat oxidizing enzymes; and, if bodybuilding is not your thing, cardio exercise on an empty stomach is thought to help the body become more efficient at using energy stores, and primarily fat.

Sounds great, right? Well, it’s not all good news - most people don't even get into the “fasted state.” When you think about it, if you eat dinner at 7pm and breakfast at 6:30am, you’ll never get the chance to get into the optimal fat burning level that the “fasted state” allows.  And that’s just the start. The bigger problem with all of these ‘on-trend, quick-fix’ diets is that the everyday experts don’t put them into the proper context and before you know it, everyone is out there “fasting” while they’re sleeping and stuffing their faces during the day thinking they deserve the whole nine since they “fasted” all night.  But that’s not how it works.  

Done in a true fashion there has been some good, albeit minimal, research so far showing that IF can help reduce weight and fat loss, improve cardiovascular health and blood pressure, but it stems from other intricate timing nuances as well as maintaining rich, and appropriate macronutrients during the 8 hour “feeding” phase (can’t be all Twinkies and beer).  For instance, IF performed with the “fasting” state occurring from 10pm-2pm with bouts of training occurring before the first meal (ex: 12:30pm-2pm training), and then a large post-workout meal directly after (and some BCAA supplementation for good measure) has seen some positive results.  However, not enough research has been done yet to make a big opinion.  But it’s worth a try and is showing to be promising.  It also, ifdone correctly, allows a person to actually “practice” what it feels like to be hungry (as well as learn the difference between being truly hungry of mentally hungry) which is a good skill for someone on the journey to weight loss and health.  

And though the theory of Intermittent Fasting may be based on good scientific findings and hypotheses based on our ancestors, once you remove the context that your friendly neighborhood Dietitian can bring, it becomes a dangerous fad.  As we continued to discuss his plan, my new friend made it clear why he found Intermittent Fasting so attractive: he had concluded that he could eat whatever he wanted and drink as much as he liked, and, as long as he stuck to his Intermittent Fasting, he would be fine.  As someone who loves technology and the latest gadgets, believe me, I know all about the appeal of quick fixes! We’re all accustomed to looking for something that will change our lives with minimal commitment and no effort. But, as so often is the case, quick fixes aren’t the answer. 

The body is a complex system that needs essential nutrients and chemicals to make it work. Dietitians study and understand how it all works together.  We can help you to reach your goals – and maintain them. But there is no magic pill, and no magic ‘science’ that, when taken out of context, will get you there in a healthy state. It’s far better to concentrate on steady improvements in the way you eat, than doing anything ‘intermittently’.  A lesson, I think, my new friend will learn the hard way.