Should You Try Intermittent Fasting?
Let’s talk INTERMITTENT FASTING!
Whats the buzz? And is it a good fit for you?
I have training and nutrition clients ask me about this all.the.TIME. So here’s a concise, easy-to-understand, scientifically-backed summary of everything you ever wanted to know about Intermittent Fasting!
You can click through the sections of this article more quickly using this handy Table of Contents…or, just scroll down and get to reading!
What Is Intermittent Fasting?
Intermittent Fasting (IF) means exactly how it sounds: fasting, intermittently.
Sometimes you don’t eat, and sometimes you do…but planned. For example, you stop eating before bed, right? And you probably don’t eat again until sometime after you wake up in the morning…unless you are a sleep-eater or often plagued by midnight stress followed by 3 bowls of Frosted Flakes.
If this applies to you - not eating when you are sleeping - than congrats! You’re already essentially practicing Intermittent Fasting, with likely an 8/16 schedule. 8 hours of “fasting” (overnight) and 16 hours of “feeding” (hours during the day where you are eating).
The thing is, with true Intermittent Fasting, you want that “fasting window” to be longer in order to reap the benefits. This is where specific models of Intermittent Fasting come in to play, with planned fasting and eating windows.
There are multiple models of IF, some more sustainable than others. Here’s a handy image you can refer back to throughout this article, but you can see that the term “Intermittent Fasting” applies to a variety of models of planned fasting and planned eating.
Sometimes the fasting window is closer to 16 hours - people do this by stopping eating earlier in the evening, and/or pushing off their first food of the day to later in the day, maybe closer to lunch time. This is a very specific model of IF called “TRF”, which stands for Time-Restricted Feeding. You will learn more about that below.
In other models, those fasting windows are over entire day or more. People will literally not eat, all day, for over days in a week.
Yes, with all forms of IF there are rules to follow. For example, to officially be in a fasted state, only zero calorie drinks (like black coffee and tea) or water are acceptable. In other words - zero calories. And all models have the time frames of fasting and eating laid out.
So what’s the point? Why would anyone voluntarily do this…what are the benefits?
Here are some reasons why IF, or TRF in particular, has become so popular:
Do you track calories/macros? With IFmore calories/volume per meal = feeling fuller and more satiated with each meal. WIN.
NOT tracking calories/macros? Intermittent Fasting: possible reduced appetite + eliminating meals/snacks = less calories consumed overall
Possibly improving health and longevity? Maybe…due to a bunch of theories stemming back to the idea that our ancestors regularly fasted intermittently due to food scarcity and a “feast and famine” way of being. There are varying conflicting studies on this, which suggests that there is no real difference in health markers and fat-loss when calories are matched (AARR December 2015, Intermittent fasting and body composition: After over a decade of research, where are we today?). And even if it does pan out one day, it’s probably only with 24+ hours of fasting, which is unsustainable for most.
Did you read that reduced-appetite thing above? Yea, people who practice the 16/8 method often report suppression in total appetite, leading to less snacking and eating more appropriate portion sizes at meals. For example, this systematic review shows that, without actually controlling the calories on individuals, TRF groups overall consumed less calories and saw a greater reduction in fat mass.
Increased focus and attention during fasting window: when the body is stressed, it releases higher levels of the hormone epinephrine (the “fight or flight” hormone). This likely leads to the feeling of increased focus and awareness people feel during a fasted state.
Common Methods of Intermittent Fasting
Let’s move on to the actual methods of Intermittent Fasting, shall we?! Below are the most common methods of Intermittent Fasting starting with my personal favorite…
The 16/8 Method (or Time Restricted Feeding- TRF)
16/8 means 16 hours of fasting, including your sleep, and an 8 hour window of eating. This method is also called Time-Restricted Feeding (TRF). Read: 16/8 and TRF are the same thing.
People will usually stop eating between 7-10 pm and not eat again until close to lunch the next day. Essentially, skipping breakfast. This is definitely the most common method of IF and many are flexible with the timing - for example, many may only fast for 12-14 hours instead of the full 16. Some may stretch the 16 hour window to 17 or 18 hours.
Another option for the 16/8 method is called Early Time-Restricted Feeding (eTRF) and is more aligned with the circadian rhythm. With eTRF, an individual would start their “feeding window” with breakfast in the morning, and have their last meal of the day early in the afternoon/evening, maybe 3-4pm. This still gives the full 16ish hours of fasting, with a different personalized structure.
I already know you are wondering…Jaime, aligning with the circadian rhythm sounds like it’s inherently better for fat-loss right?
Not really…
eTRF does seem to have a slight edge in improving glycemic control (which is your body’s ability to control glucose levels in the blood), however the studies are done on inactive individuals - adding exercise into the daily routine could likely override the benefits of eTRF. (AARR September 2019, Early Time-Restricted Feeding: Hype vs. Data ) This is a classic situation of possibly missing the forest for the trees. “In the bigger picture, what matters is the ability to adhere to the diet in the long- term, regardless of the chosen meal distribution pattern.” (Alan Aragon, Sept. 2019)
The Warrior Method
Very similar to the 16/8 Method, but with a longer fasting window. This method also falls under the title of TRF. People who follow the Warrior Method will have one, maybe 2, giant, calorie dense-meals in a day, all within a 2-4 hour feeding window. This method can be very triggering for an individual who has previously suffered from an eating disorder, disordered eating habits, or any sort of food restriction practices in the past. I personally do not recommend this method for most people!
The Eat-Fast-Eat (or 5:2) Method and The Alternate Day Method
In these methods, fasting is done over entire 24 hour periods - either alternating day, or on an eat-fast-eat rotation. These methods are known for being harder to adhere to for most. Meaning that, while there may be more evidence to support the metabolic health benefits of IF utilizing these models, them being extremely unsustainable for most people makes them methods I wouldn’t personally recommend, especially for women. Likewise, these methods could be very triggering for an individual who has previously suffered from an eating disorder, disordered eating habits, or any sort of food restriction practices in the past. In case you didn’t read between the lines…I don’t recommend either of these methods. :)
The AM Workout Method
I made this one up. No lie. :) This isn’t a method you’ll likely see anywhere else (because it’s not even technically fasting!).
So, a while back I was enjoying the 16/8 model of IF (TRF) but I was also working out, like heavy strength training, in the mornings. Doing this fasted was rough and not recommended. eTRF was also not something I was interested in (#momlife doesn’t pair well this method well, IMO). So my solution was to have a workout shake including protein powder, Gatorade powder and creatine during my morning workouts, and not consuming actual food until lunch. This ensured I had glucose and amino acids circling my system for energy, strength and muscle protein synthesis during my training sessions while also being able to have the bigger meals and satiety later in the day that TRF offers. No, this method does not officially qualify as Intermittent Fasting because it involves consuming calories in the “fasting” window. But if you want to try TRF for the meal-structuring benefits, but eTRF wouldn’t work for you either, this is a possible work-around. I have coached some clients through this exact method with success (please note that cardio activity in a fasted state is totally acceptable and common - it’s just strength training that I don’t recommend fasted).
Intermittent Fasting for Women
Yes. It’s different!
Frustratingly, as much research as we have on Intermittent Fasting, a large majority of studies have been done on men. Or rats…
We know, without a doubt, that a woman’s body functions very differently than a man’s (and also different than a rat’s…). Also, Time-Restricted Feeding (TRF) research is a little behind the ball since it is still a relatively new concept, though so far research looks promising.
While I personally really enjoy TRF, I think it’s very important for women to not only be aware of the research (or lack there of) on hormones and Intermittent Fasting for women, but to also have a strong flexibility mindset when approaching any method of IF.
While we still don’t have enough solid research for me to give a solid recommendation one way or another, there’s definitely enough evidence to show that women should absolutely proceed with caution and awareness when approaching IF, specifically the more extreme methods described above. As it turns out, our hormones don’t respond to energy restriction and stress the same way men’s do (shocker!). For example, in some of the few studies that compare men’s and women’s responses to IF, there is evidence showing IF seems to trigger a greater stress response in women, as well as a slightly-impaired glucose response. (Keep in mind both of these referenced studies were done on an alternating-day method of IF) However, fasting may have a positive hormonal effect in women with PCOS.
I love this analogy - think about our ancestors, living in times where hunting and foraging for food was necessary. For men, hunger and stress could have signaled in increase in metabolic rate, attention, focus and energy because they needed to go hunt and forage to keep the family alive. Many studies support this possible response in men. Contrastingly, women could have had a very different response, conserving energy, decreasing metabolism and energy expenditure to protect fertility as well as their own lives as care-takers for the next generation.
Ultimately, research shows that women’s bodies may be more sensitive to energy balance changes. And when women’s bodies detect those changes, hormonal cycles can be completely thrown off. If you are a woman reading this right now, I highly suggest reading this article by Precision Nutrition on Intermittent Fasting and women. It does a fabulous job of explaining, in layman’s terms, the research we have and how you can test if IF would be a good fit for you: https://www.precisionnutrition.com/intermittent-fasting-women
Should women avoid IF completely? Not necessarily! My recommendations for women are:
Only consider TRF (16/8) - Other methods of fasting are too extreme, not sustainable, and likely not inline with our body’s hormone regulation system.
Go slow - push back your “fasting window” 1 hour at a time until you reach a place that is comfortable for you.
Be aware - pay attention to your body, your feelings, and your mental and emotional health around food and exercise during this process of exploration.
Be flexible - Remember that in order to sustain something, it needs to fit into your lifestyle. Be willing and open to make changes to your system when it’s not working, and also be willing to be flexible in times where it doesn’t make sense.
What I Love and Hate About Intermittent Fasting
I am careful when recommending IF-TRF to nutrition clients, and only do if I have determined it to be a good fit. Currently, only about 30% of my current training and nutrition clients follow TRF. I also flow in and out of IF myself, always with the 16/8 (TRF) method. Typically I practice TRF when I am intentionally eating at a calorie deficit while cutting down on body fat. Here’s what I love and hate about it, from my and my clients’ perspectives:
Love
Overall, my clients love it. They find it much easier to manage their daily intake during TRF.
We find it so much easier to stay within caloric range! If not doing TRF and trying to lose body fat or even maintain weight, we find ourselves having to use willpower all day to keep portion sizes small. With TRF, we instead concentrate that willpower all in the morning and feel relatively full the rest of the day. This, right here, that willpower thing…that’s it for me. So worth it.
It’s nice to enjoy bigger, more satiating and calorie-dense meals. We can actually fit mac and cheese or a cupcake or another “calorically expensive” food into our deficit calories without it leaving us feeling starving.
Less meal planning and less meals to track!
The increased focus and attention during morning work hours is true. Huge plus!
TRF works super well for social events and travel (or any situation when we might want to leave room to eat more food later in the day).
Overall snacking is WAY down for me and my clients during TRF.
Hate
I get hangry. HA! It’s fine when I am working but I am a much less patient mom when I am restricting food (duh). This is a pretty big negative that I struggled balancing, but I have figured out how to handle it - awareness (usually I am able to adjust my mood with this simple step) and flexibility (if I am hungry earlier or if there is a pancake breakfast, I eat, damnit.) Also, your body gets used to when you eat so often times, this is a bump that passes with time. My clients and I find the hardest hangry-hours to be between 9:00-10:30 AM, at which point it totally passes.
Sometimes, I feel very hungry all morning. Waiting to eat is hard and irritating in these times. This usually happens due to the calorie deficit overall, and not TRF itself. My body just realizes that it’s not getting what it used to.
Sometimes I have to adjust my strength training sessions to accommodate TRF, depending on what life looks like at the time.
That’s it. I overall love TRF.
Some Things to Consider Before You Try Intermittent Fasting
If you’d like to try Intermittent Fasting, in any form, here are some things to consider before diving in:
Any form of Intermittent Fasting requires some level of food control or restriction. This is true with any diet, diet structure, or goal towards eating less overall. Introducing restriction into your relationship with food can be triggering for those who have or do suffer from eating disorders or disordered eating habits. Proceed with caution, and consider seeing a therapist or counselor if you struggle with this.
Multiple studies on blood lipid levels and other health markers have been done on varying forms of IF and there is still no consistent message on if IF is actually better for health and longevity when calories are matched in a continuous-eating model.
That being said, among the studies there is still a consistent theme of IF being better for fat loss, insulin sensitivity, cholesterol and overall health for overweight and obese people. This could very well be due to IF creating a structure that makes it easier to stick to recommended calorie allotment, vs the theory that IF itself is inherently boosting metabolism and health markers.
This one is cool - The 16/8 method of IF seems to be superior in maintaining lean mass compared to standard daily caloric restriction. This may be due to the elevated levels of Human Growth Hormone (HGH) when fasting.
Overall, in relation to fat loss, continuous energy restriction and IF seem to produce similar benefits. Meaning…
>>> Intermittent Fasting is not a magic method.<<<
In other words, many studies show no difference in fat-loss with any form of Intermittent Fasting, when calories across the board are matched. Take a look at this study, which used resistance trained females - there was no difference in muscle/fat loss or gain (which also challenges the idea that protein should be spread across the day for maximizing anabolic effects, but that’s another topic). However, TRF, with a feeding window at any time of the day, does seem to have a slight fat-loss edge when calories and macros are not being controlled. This is likely due to the suppression reported with TRF.
So…just like other diets and dieting structures, IF/TRF is not inherently better for fat-loss or health. While there are many clear benefits, as with anything, the most important factor is whether the method is sustainable to the individual and their lifestyle.
Tips to Make Intermittent Fasting Work for You
The only Intermittent Fasting structure I can fully back for my clients is the 16/8 or TRF method. If you are ready to try it, awesome! Here are some tips for you:
Start with pushing your “fasting window” wider one hour at a time. For example if your window is currently 9 hours, push it to 10. Then 11. Work up to 14-16 hours and stop when it feels comfortable and sustainable for you. There are no “rules”.
Black coffee and tea (but especially coffee) help blunt hunger. Initial hunger, in the morning especially, is normal. My clients and I find around 8:00-10:00 am to be the most challenging in terms of hunger, and then it dissipates afterwards. Sometimes I don’t even feel hungry when I eat my pre-workout oats at 11am. That being said - sipping on black coffee or flavored teas all morning really helps with that feeling!
Be flexible!!! You should aim for 80% in everything in life and this is no exception. Maintaining rigid rules for yourself will result in frustration and failure. If the hunger isn’t dissipating, eat. If hormones are raging, eat. If the whole family is eating something yummy in your “fasting window”, eat. If you are traveling and the hotel offers a free breakfast buffet before your full day of sightseeing, don’t stockpile hard-boiled eggs and bread in your backpack for when your “feeding window” opens…just EAT. (yea, that was me…)
Avoid strength training while fasted. You can do this by adjusting to the AM Workout Method, or by changing your eating/training schedule (fasted-cardio is fine, just remember there are no added fat-loss benefits to fasted cardio, despite what you may have heard).
But train fasted if it works for you. Yep - while I don’t recommend it, some clients prefer training with zero food in their stomachs. Others just feel more energetic, or the lack of food in them doesn’t seem to bother them. If this is true for you, no worries. Like I said, there’s no “rules”. You might not gain as much strength or muscle mass training this way, but that also might be fine for you. So - you do you…just armed with the right knowledge.
