Intermittent fasting’s popularity has been on the rise for quite a few years now. Avid intermittent fasters claim that it is the “magic” solution for fat loss & those looking to maintain their body weight.
Despite its popularity, intermittent fasting is NOT the magic pill for fat loss. Moreover, it’s not the act of fasting itself that guarantees fat loss, but more so the calorie deficit it creates when you shorten your eating window.
It is a tool that can be used by certain individuals to help control daily caloric intake, however, it is not for and shouldn’t be used by everyone.
So let’s dive into why intermittent fasting isn’t the end-all, be-all for fat loss.
So what even is IF and how does it work?
There are many approaches to intermittent fasting, but the most common is the 16:8 approach. This means you have an eight-hour eating window and a sixteen-hour fasting window. Most of that fasting window is meant to occur while you’re sleeping, so many choose to have their eating window set between the hours of 1-9 PM and some between 12-8 PM.
There are some that choose to fast for 24 hours multiple days of the week, people who fast 18 hours and eat in a 6-hour window, or fast 14 hours and eat for 10 hours. The method may vary but idea is to restrict your eating window regardless of its duration.
With IF, there aren’t specific guidelines to what you can and cannot eat, but only when to eat.
Many people advocate for this approach as a weight loss diet because some people prefer to restrict their eating window to help restrict calories versus restrict their calories while eating in a larger window.
Is IF a good tool for fat loss?
Honestly, it depends.
It’s hard to pinpoint one single diet being the key to fat loss success for every single person on Earth because we’re all SO different.
Our bodies have:
Different hormone profiles
Different nervous systems
Different psychological make-ups
Different training stimuli
We’re literally different humans, so what diet works best for you, won’t work best for me, or your mother, etc.
But for the sake of this explanation, let’s say you want to try IF for fat loss.
Let’s say you typically eat breakfast at 7 AM and finish dinner between 8-9 PM. With the most common approach to IF (the 16:8 approach), you’d be cutting your eating window almost in half.
With that being said, you’d more than likely be skipping breakfast and maybe a snack in between breakfast & lunch until you reach the beginning of your eight-hour eating window. Meaning, you’d be decreasing your food consumption by skipping a whole meal and maybe a snack.
By decreasing your daily caloric intake, whether it’s intentional or not, you’re putting yourself in a calorie deficit.
Conversely, you could restrict your eating window with intermittent fasting BUT not see fat loss if you’re still eating at your body’s maintenance or eating in a calorie surplus.
Needless to say, it’s not the act of fasting itself that leads to fat loss, but the calorie deficit it oftentimes creates in shortening our eating windows.
But what does science tell us about the effects of IF?
Intermittent fasting has been researched, however, most studies have been done on animals or with smaller groups of human participants.
One study found that intermittent fasting leads to fat loss and improved blood pressure in obese participants (Gabel, 2018). However, participants in this study were also in a calorie deficit of about 300 calories over the course of 12 weeks without intentional calorie counting.
Another study done in 2017 by the International Society of Sports Nutrition indicated that fat loss using intermittent fasting is NO different than those eating throughout the duration of the day while eating in a calorie deficit.
So scientifically speaking, intermittent fasting isn’t the magic solution to fat loss. If you’re in a calorie deficit you will lose body fat. No matter how big or small your eating window is.
Who might consider using IF?
Intermittent fasting might be a great tool for some.
For instance, if you:
Don’t have an appetite and don’t train in the morning.
You prefer larger, less frequent meals.
You are already managing your stress levels.
You have a strong recovery game.
You can’t commit to tracking your food intake consistently.
You want to control your caloric intake without tracking for a period of time (i.e. while traveling).
If any of the above describes you or where you’re currently at on your health & wellness journey, intermittent fasting might be a good strategy for you.
However, fasting is a stress on the body. Although small doses of stress are good for us (i.e. training stress), there are certain individuals or scenarios that fasting will not be the best option for.
Train early in the morning, your body will need fuel pre & post-workout to optimize your performance & recovery.
Do you any type of high-intensity exercise (i.e. CrossFit, Orange Theory, HIIT).
Are working to improve your hormone imbalances.
Already have a difficult time eating enough food throughout the day.
Live a high-stress lifestyle either at work, at home, or both.
Enjoy eating breakfast in the morning.
If any of the above describes you or your lifestyle, fasting is probably not the best option for you. Because again, fasting is a stress on the body. If you have a stressful job, aren’t managing that stress, not sleeping 7-8 hours each night, and are doing high-intensity exercise, the additional stress of fasting on your body will not outweigh any benefits that come with it. In fact, you might be doing more harm than good.
Also, if you’re a morning person, love waking up and making breakfast, intermittent fasting probably isn’t for you either. When trying to figure out what kind of diet will work best for you, it will always come down to the diet you can adhere to long-term. If fasting leaves you feeling miserable & starving in the mornings, your adherence will falter after a few weeks.
What if I want to gain muscle?
There is definitely conflicting research on whether or not intermittent fasting impedes muscle growth, or not. One study done in 2016 showed a decrease in fat mass and maintained muscle mass in resistance-trained males while using the 16:8 intermittent fasting approach.
However, it’s important to note the participants in this study were eating an ample amount of protein AND were resistance training throughout the study. Thus, creating an optimal environment for maintaining muscle mass.
While some studies show no amounts of lean muscle mass loss, there isn’t any evidence showing muscle mass to be gained while intermittent fasting. This is mostly due to the fact that if you want to put on size (aka gain muscle) you need to be eating more than you’re expending daily.
By cutting your eating window short, you’re limiting your opportunities to consume calories & get in an adequate amount of protein to support muscle protein synthesis.
While it isn’t impossible to put on muscle while intermittent fasting, it is definitely less than ideal in most cases.
The effects of intermittent fasting in women
Women have less resilient endocrine systems than men. Meaning, our hormones are more sensitive to changes such as fasting.
Women have naturally fluctuating hormones as we go through our monthly cycles, hit puberty, and go through menopause because we’re responsible for carrying & creating life making our bodies more reactive to stress. Fasting is a stress on the body, so if a woman already lives a high-stress lifestyle, works out frequently, and decides to try intermittent fasting, it wouldn't be out of the ordinary for her to see worsen PMS symptoms and adrenal dysfunction.
Does this mean all women shouldn’t intermittent fast? Nope. I just always recommend women air on the side of caution when exploring intermittent fasting. If our bodies are too stressed out, they will not go through our natural hormone cycles throughout the month. This is also why you’ll see super lean bikini models, or leaner female athletes lose their periods.
With that being said, women that are struggling with hormone imbalances might want to opt for not using intermittent fasting as a strategy for fat loss and look to eat balanced meals throughout the day to support a healthy endocrine system.
As always, consult your medical practitioner before implanting intermittent fasting into your diet to ensure it’s a good & safe option for you.
The bottom line
Intermittent fasting is just a tool that can be used to create a calorie deficit, just like any other diet out there. It’s definitely not a magic solution for fat loss and it’s not for everybody. It can be a helpful tool for those that don’t want to track their food consistently to help create a calorie deficit.
Everyone’s nutritional needs are unique to them which is why we preach individualized nutrition here at Clar-e-ty. Your nutrition plan should fit into your lifestyle and should be something you can see yourself adhering to for a prolonged period of time.
If you need some guidance on how to make your nutrition start working for you, check out the links below and apply to work with a Clar-e-ty Coach today!
Aragon, Alan A et al. “International society of sports nutrition position stand: diets and body composition.” Journal of the International Society of Sports Nutrition vol. 14 16. 14 Jun. 2017, doi:10.1186/s12970-017-0174-y
Gabel, Kelsey et al. ‘Effects of 8-hour Time Restricted Feeding on Body Weight and Metabolic Disease Risk Factors in Obese Adults: A Pilot Study’. 1 Jan. 2018 : 345 – 353.
Moro, T., Tinsley, G., Bianco, A. et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med 14, 290 (2016). https://doi.org/10.1186/s12967-016-1044-0
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