As a personal trainer and fitness coach, I am often asked about the latest diets.
Over the course of the years, I have heard about the Atkins, The South Beach diet, Paleo…and now of course, intermittent fasting! Curious about it?
Here are my 2 cents on it!
After all, if Jennifer Aniston released her guide on it, I can have an opinion too!
And as I work in sports and nutrition, not in acting, mine is a bit lengthier.
Let’s dive in:
First how does it work?
The different types of intermittent
When it might be helpful or harmful!
Few pointers to experiment with it safely.
And of course, the million-dollar question: Will I lose weight?
1.What is intermittent fasting?
Fasting means going without calories/energy from food and drinks for a period of about 8–12 hours (or more).
So, in a sense we are ALL already doing it partially, unless you eat while you sleep!
Once our bodies have digested and absorbed the calories from our last meal, we gradually enter the fasting state. When we are in this state, we rely on fuel from stored energy from glycogen in our liver + eventually body fat.
Intermittent fasting (IF) means simply that we are going to extend this period before and /or after the sleep period.
2.The different types of intermittent fasting. It comes in many shapes and forms.
TIME-RESTRICTED EATING / TIME-RESTRICTED FEEDING
This involves only eating during a certain period every day. Different ratios are being used:
12:12 Some people fast for 12 hours and then eat normally during the other 12 hours.
14:10 Fast for 14 hours, eat normally for 10 hours.
16:8 Fast for 16 hours, eat normally for 8 hours.
And the most extreme:
20:4 Fast for 20 hours, eat normally for 4 hours.
ALTERNATE-DAY FASTING
This involves eating normally for one day, then fasting the next, and repeating!
FASTING-MIMICKING DIETS This isn’t true fasting, but rather having days with very low-calorie intake (200–500 calories/day).
FASTING… NOW AND AGAIN
There is no structured schedule: in this case, people can simply wait a little longer to eat, stop eating earlier than normal, or skip a day of eating.
This one is my favorite as it is flexible. You can plan to do it on days you don’t have a lot on your plate, because your energy level won’t be optimum.
You can use it to support your body when needed, rather than being the slave of a rigid concept. Here are some examples:
- To give a little boost to your immune system: when you are fighting a coming cold, stomach bug, or reduce inflammation.
- After indulging the previous day in food and/or drinks.
- Simply for the days you feel off and your body needs to go into repair/reboot mode (digestion is time and energy consuming).
Why would someone do intermittent fasting?
While the attention the IF craze is getting seems to be over the top, this type of lifestyle isn’t new.
People experiment with IF for a number of reasons:
They want to eat more mindfully. Food tastes pretty good after a period of fasting, and they welcome the chance to practice gratitude for a meal. As a distance runner, I totally validate that real food is such a treat and tastes awesome after hours of deprivation.
Some people like the way that IF aligns with their schedule or unique appetite cues. For some folks, it’s just a natural eating pattern.
FYI:I have a client who eats one meal a day, is super active for his work but is still overweight. However, his dinner calories would easily combine the ones of a healthy lunch and dinner combo for another person.
Others want to get more comfortable with hunger and fullness cues. I am thinking, for example, of people who are afraid of being hungry, who are snacking all the time, and who have lost what physiological hunger feels like.
Let’s face it, in the US access to food is everywhere, at any time. IF can be a good exercise to learn the difference between a craving or emotional hunger and a real physiological hunger.
A good number of people do it for religious reasons as part of a structured celebration for several days like Yom Kippur, Lent, and Ramadan…
Note that in all these scenarios, it takes dedication and practice! They do it for a higher purpose rather than following a strict diet. They made it part of their lifestyle, with probably lots of trial and error, at the beginning.
But the most people asking me these days, see it as a way to lose weight and fat!
First, I wonder how many of them studied in advance the demands, the ways and ratios (mentioned above) to use it, and its consequences.
The potential consequences on your mind, body, lifestyle, and exercise routine.
I know the suspense is killing you, you just want to know, if it works for weight loss!
Bear with me, as these variables will help you to have your own opinion on the subject.
When it might be helpful or harmful!
NUTRITIONAL DEFICIENCIES: Many diets focus on what to eat, but intermittent fasting is all about when you eat during a specific time.
Hum, that’s a bummer, it still doesn’t educate or help us with the quality and quantity of food.
Are you going to be able to have a healthy intake after hours of fasting, meaning hitting all your macros (healthy fats + carbs + proteins)?
Or will your mind crave comfort foods? You can easily go overboard with calories within the period of time allocated to eat, since you have been fasting and restricting beforehand.
Especially when you go for the most aggressive protocol with a really small window to eat, it requires a lot of willpower and discipline at first.
MINDFUL EATING: or conscious eating, is the practice of being fully attentive to your food, your feelings, your hunger, and your satiety cues. IF might be helpful for people who snack here and there without noticing, all day long! As:
-It puts boundaries and timing in place.
- It provides more awareness to our physiological versus emotional needs.
MOOD AND FOCUS Some people report improved mood and focus on IF.
I, myself experienced some mental clarity and focus. We all think better when our stomach is empty rather than digesting, but I did not say starving! Which can be the case at the end of the fasting period.
But 90 % of the time I am frankly hungry + angry. All I can focus on is food and nothing else! It’s an understatement that I am irritable and feel weak physically.
For people with insulin sensitivity that need to monitor the steady management of blood sugar levels, I would not recommend these drastic changes.
HORMONAL DISRUPTION IF is a stressor—a potentially healthy one, but still a stressor especially at the beginning. For women who are already relatively lean, IF may disrupt normal hormone levels, particularly reproductive and thyroid hormones.
Also, if you are pregnant, or trying to be, and don’t need to lose weight, it’s NOT the right moment to try!
POTENTIAL FOR DISORDERED EATING. If you are already a type A person: counting calories in and out, data driven, stressed and borderline obsessive about your weight or losing weight. This method won’t bring you peace of mind. You don’t need another stressor.
We need low levels of stress to promote healthy weight, not the opposite! I see it as counterproductive for this category of people, as you can become overly obsessed with the eating windows.
Speaking of stress and discomfort: it’s not always easy to socialize and eat out for lunch and/or dinner. You need to plan around your social outings with friends and family or you will end up staring at the plates of others while eating. Awkward!
SLEEP: Sleep and diet experts suggest that a light dinner promotes a good night’s sleep and eases digestion! You don’t want to feel stuffed before bedtime, but you don’t want either to wake up in the middle of the night with a growling stomach.
The quality, quantity and timing of your last food intake becomes critical.
WORK: for people with irregular schedules (which tends to be more and more the case), people traveling a lot (add different time zones on top!), or with jobs demanding a lot of focus (operating planes or on patients). Once again, you will have to plan accordingly!
Intermittent fasting and exercise performance: My favorite topic on the subject!
While you may burn more fat if you exercise during intermittent fasting, it’s also possible that you’ll have less energy, stamina and endurance and won’t be able to work out as hard (Especially for longer sessions) It sounds counterproductive to me!
There’s no way around these core concepts:
Carbs fuel your muscles.
Carbs are partially converted to glycogen, which is a form of energy stored in muscles.
This energy helps to power your workouts.
If you don’t have enough food in your system, there is no energy, no power, no focus in any sports you practice but especially in any endurance sport.
For athletes (pro or not) and highly active people (for work, lifestyle or sport), IF is not providing enough consistently available energy or nutrients to support performance or labor work and recovery (because you may not be allowed to eat after, if outside of the window)
As an athlete myself, I am critical of strict and/or long-term intermittent fasting, or a number of reasons:
-Physically and/or mentally. It’s not a pleasant experience to push your body under these conditions. You are sacrificing the quality of your work out. You won’t run as fast, you won’t lift as heavy as you do
-If you are trying to build muscle mass, IF is counterproductive.
-Experimenting with IF and doing endurance sports can even be dangerous. When your blood glucose is crashing during or after exercising, it goes FAST! And sometimes beyond control. You are going to hit the wall sooner or later.
This is particularly important for anyone with type 1 and 2 diabetes or metabolic syndrome. They need to monitor their blood glucose levels when they work out, if you add IF in the loop it will be hard to incorporate.
IF is impractical to implement for people who have restricted time to exercise. They try to
fit it through work, family, social time and exercise routine…now adding fasting bring it to another level of complexity!
I gave you a number of Pros and Cons, so you can count how many you have on both sides to see if it’s worth trying! In case you want to give it a try,
Here are few ideas to experiment with it safely:
Start with a flexible approach and a generous window like a 12-hour fast window (or even more) We all can benefit from having a last meal early with no snacking after – I am talking to myself too!- And slightly delay your breakfast time to get the 12 hours of fasting.
Stay hydrated. Drink plenty of water as well and other non-caloric beverages that include electrolytes. This can help manage hunger while also preventing dehydration.
While eating, eat well! Obviously, this will be the key element between losing weight or not. Let alone prevent nutrient deficiencies.
Keep the intensity and duration of your trainings fairly low on fasting days.
Never forget that you are experimenting with your blood sugar (glucose), so it is a good idea to monitor how you feel and pay attention to these symptoms: mild dizziness, light-headed, nausea, or weakness. Keep some carbs, like a cereal bar, with you for emergency use if needed.
If you experience many episodes, is it a good idea for you?
Implement it when the timing is right. The human brain consumes about 120 grams of glucose per day to maintain normal physiological conditions. This is about 25% of the body's glucose. So don’t start when you are doing tasks where concentration and energy are important and over a number of hours (studying for exams, operating machines, driving long distance…) Or when you experience already a good amount of stress in your life.
Will intermittent fasting help you to lose weight? Once again, the answer is… it depends.
It all depends on WHAT you eat and in which quantities during the allocated time.
Like with any other restricted diet.
It is a buzz, until the next one. It is presented like a weight -loss magic pill!
It’s not!
It is not a simple task to put into practice and implement (will-power, logistics, timing, hunger to master, work, and social activities…)
I see it as beneficial here and there (a few hours during the day or some days when needed) but not the strict version. You can simply use it as one of your tricks or tips for your health, but don’t let the principles rule you.
Take what you need, what might serve you. End of story!
So, now what’s your idea on IF? Could it help you?
Don’t hesitate to share your failure or success stories as I am always curious about them!
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