People either seem to love it or hate it.
Some lose weight through it others don't notice a difference.
A few feel more mental clarity and energy, a few feel brain fogged, anxious and get hormonal disruption.
So what is it now?
Should you do it? Here is a bit of a rundown on Intermittent Fasting, some of the research and facts around it and a few pointers how you might be able to find out whether it is right for you or not.
What is Intermittent Fasting?
Just a few years ago, people in the fitness space used to believe that one should be eating 5-6 small meals per day.
Now fasting followed by 1-2 large meals seems to be all the hype.
The central idea behind the implementation of intermittent fasting (IF) is to reduce overall calorie consumption, ideally resulting in weight loss.
Typically, IF protocols will involve eating nothing for a period of 16-20 hours, followed by an eating window of 8-4 hours of usually larger meals.
There are many other protocols for example 1 full day of fasting followed by 1 day of "regular" eating and so on.
IF and Weight Loss
In a fed state, the human body uses insulin to bring glucose into cells to manufacture energy.
During periods of fasting, the body's level of blood glucose significantly decreases.
This lowers insulin release and increases insulin sensitivity, resulting in increased fatty acid oxidation.
Since IF may decrease both glucose and insulin levels, the body could potentially use stored fat as fuel. (1)
Sounds perfect, right? Not so fast.
A short-term fasting study, covering 15-30 hours, also demonstrated an increased rate of protein breakdown.
The last thing that we want is to lose any of the hard-earned lean body mass we work so hard for.
We don't just want to become smaller, weaker, less healthier versions of ourselves. Remember, the goals is not WEIGHT loss per se, it is FAT loss. (2)
Other studies show that, purposeful fasting of 20 hours or more, even if only for two weeks, may invoke a starvation-related decrease in resting metabolic rate.
A decreased metabolic rate may slow down the weight-loss train and quickly derail your weight loss...
While much of the research does show benefits from fasting for a healthy insulin response and gut health, many studies also indicate that these benefits are the same whether you fast 10-12 hours (so sleeping) or 16-20 hours (3).
IF and Adherence
In any diet ADHERENCE, so your ability to stick with the plan, needs to come first.
The best plan is worthless if you cannot adhere to it long term. This is where IF either shines or fails.
Particularly people who have always had a hard time getting some kind of breakfast down tend to love intermittent fasting.
Finally science is backing up their natural inclination not to eat in the morning.
People who are incredibly busy in the morning also enjoy not having to make time to eat when they just want to get things done.
Of course it also helps those who usually tend to snack until late at night (usually junk) who then start fasting in the early evening, because naturally that will make it easier for them to limit their calories.
However, if you are someone who loves to snack, gets joy out of multiple small meals (as opposed to fewer larger meals), someone who tends to get jittery without regular food, particularly carbs (you know who you are :) IF is likely not for you.
Furthermore, for some people fasting for a while can actually lead to binge eating patterns later on, simply through the earlier restriction and can therefore lead to weight gain and an unhealthy relationship with food.
IF and Hormones
The latter type of person is usually also someone who is more insulin sensitive (mostly females), who tend to get 'hangry' when not having eaten in a while.
This is a pretty clear sign that IF would do you more harm than good, particularly your hormones (as fasting could increase your cortisol levels, when your body perceives the absence of food as 'stressor').
Furthermore, if you have menstrual irregularities that you are trying to fix or you have a missing period altogether, IF is most likely not for you.
If you want to learn more about IF particularly for women and how it affects their hormones across the lifespan (teenagers, around ovulation, menopause etc.) check out this article HERE.
IF and Protein
Limiting your eating window can also make it rather hard for some people to get all their protein in.
If you have a protein goal of 200g and you only eat 2-3 times per day, that means you need to ingest large amounts of protein in one sitting, which is not ideal for digestion in most cases. It is also not ideal if that means you need to train in a protein depleted state or you won't get any food for numerous hours after your training (when your body is most receptive to fuel for recovery).
Is IF for you?
Ask yourself these questions:
- Do I prefer more frequent smaller meals or fewer larger meals?
- Do I find it easy not to eat anything in the morning?
- Do I notice drops in mental or physical performance from fasting (brain fog, lower training output)?
- Do I (potentially) have any hormonal issues or have I had any in the past (such as adrenal fatigue, menstrual problems, low testosterone...)?
- Do I struggle reaching my protein goal?
- Do I tend to overeat at night and would benefit from having a food "cut off" time earlier on?
...
Answer these questions openly and honestly and you will come to your own conclusion whether IF could be helpful or harmful for you or whether it really wouldn't make a difference at all.
As so often, I encourage you to view yourself as your own best experiment. Give it a go for a couple of days and see how you feel, then you will be able to form your own opinion on the matter.
Also remember that just because someone 'defined' IF as 16-20 hours of fasting does not mean it has to be that or not fasting at all. For you the ideal amount of hours could be 14. Or you could do a hybrid of 16 hours of fasting + a protein shake outside of that window simply to help you reach your goal.
And lastly, still keep in mind that, fasting or not, total daily calories and macros are what matters the most, whether you eat them in a 8 or 12 hours window does not matter that much for weight loss, but it will matter for adherence, energy and performance.
