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Intermittent fasting. You’ve probably heard about it before. Alternating between creating an energy deficit while eating more on the other day. What does such a diet actually look like and what are the different possibilities? More importantly: How do you determine if this is the right strategy for you?
“Nog even over intermittent fasting”
Last May, I wrote an article about alternate-day fasting. It was based on research that concluded that intermittent fasting is just as effective as a normal diet as long as the energy deficit over the entire period is equal. However, that research only focused on one possible way of intermittent fasting. So, I promised:
I will soon write a separate article that discusses multiple studies on different methods of intermittent fasting.
That’s why I’m writing a more extensive article about the various aspects of intermittent fasting.
Is intermittent fasting the right strategy for you?
In 2010, I was introduced to intermittent fasting (IF) by Martin Berkhan. At the time, I was skeptical if this would be right for me, but I decided to give it a try.
I, too, had achieved good results with it, and at one point, I was firmly convinced that IF was a suitable strategy for everyone.
Several years, experiences, and studies later, I have changed my stance. I have realized that intermittent fasting is not for everyone, and now I rarely recommend this strategy to my clients. I will explain why this is the case further. First, I want to briefly explain what intermittent fasting is, which popular diets are based on it, and the pros and cons of intermittent fasting.
What is intermittent fasting?
Intermittent fasting is mainly used as a method to lose weight. Periods of fasting are alternated with periods of eating. This is also called interval fasting.
During the fast, only calorie-free drinks are allowed. Think of water, coffee, tea. The duration of the fasting period depends on which diet you follow. The fasting periods of current diets range from (daily) 14-19 hours of fasting to occasionally 24-36 hours of fasting.
The Dutch Health Council states that breakfast and regular eating are important for health [6]. Looking at the popularity of fasting and the diets developed from it, it is interesting to take an objective look at it. This mainly emphasizes meal regularity and not so much macro-product choices.
To indicate the effectiveness regarding weight loss as well as the effect of intermittent fasting on health.
Also read the article: The 16/8 diet. 16 hours of fasting, 8 hours of feasting. Does it work?
The most popular intermittent fasting programs
There are several diets based on IF. Well-known fasting diets include Alternate-Day Fasting (ADF), Eat Stop Eat, The Fast-5 diet, and Leangains.
Before the fasting period begins, it is important to consume a relatively large amount of food. This to stay well-satiated during fasting and to maintain a positive nitrogen balance. Of course, calorie intake must be taken into account. It is possible to gain weight with such a diet if too many
calories are consumed!
Intermittent fasting is
mainly used as a method to lose weight. By restricting your food to certain periods, it can reduce your calorie intake. This because you are allowed to eat less often and your food consumption automatically decreases.
Consuming fewer foods = consuming fewer calories.
The benefits of intermittent fasting?
- Sustainable weight loss and maintenance: Intermittent fasting can help you with sustainable weight loss or maintaining weight. Due to the low meal frequency, you have a larger calorie budget per meal (when you are allowed to eat, you can eat more).
- Better satiety: Larger meals generally help you feel better and more satisfied for longer. Of course, this also depends on your food choices. If you have a big appetite, larger meals are simply more practical for getting full faster.
- Calorie banking: Intermittent fasting can build up a large calorie buffer for a specific event (restaurant visit, birthday, holidays, etc). If you regularly encounter social eating occasions in the evening, it can be a good strategy to save calories during the day.
- More flexibility: It can be practical to prepare and/or take fewer meals.
- No need to force breakfast: If you have to force yourself to eat in the morning, it is ideal to postpone your breakfast. Another advantage is that you save time and have a larger calorie buffer.
- Health effects: Regarding the health effects of intermittent fasting, more research needs to be done to be able to say something about it.
The drawbacks of intermittent fasting?
- Eating disorder (history): Some individuals may develop an eating disorder due to intermittent fasting by saving calories and turning it into a feast. Three big meals, for example, become only 1-2 big meal(s). If you have a history of an eating disorder, intermittent fasting can trigger or even worsen it.
- Low appetite: Consuming many calories in limited meals can be a big problem for some individuals. It is better to eat multiple meals a day.
- Increase food consumption: If you have poor insulin sensitivity (usually individuals with overweight), early breakfast can help maintain blood sugar control. This results in more control over appetite. Glucose tolerance and insulin sensitivity in the muscles are higher in the morning than later in the day [1]. Fasting can thus increase food consumption during the day.
- Lower energy expenditure: During your fasting period, you are inclined to move less, resulting in lower energy expenditure. This is not a problem if you have a desk job, but it is detrimental if you are active during this period. Being active during a fast causes you to unconsciously move less. Think of moving your feet, hands, staying seated longer, etc. When you eat a meal before the activity, you automatically (unconsciously) move more. This means that your energy expenditure at the end of the day is lower if you do your activities while fasting.
- Less energy: When you are active during the fast, this can have a negative impact on your energy levels. You may feel dizzy or less fit/energetic more quickly.
- Slower resting metabolism: Fasting for longer than 20 hours slows down your resting metabolism [2]. This means that you burn fewer calories during the day than if you were not fasting. How much this is depends on how active you are during your fast. The less active you are, the smaller the effect on your resting metabolism.
- Muscle growth for beginners: If you are a beginner and engage in strength training, you take longer to recover from your muscle damage. You have an increased protein need, and you want to keep feeding your muscles for as long/often as possible (within what is optimal). Training during fasting and then not eating afterwards is also completely illogical.
- Muscle loss: Prolonged fasting (20 hours or more) can result in muscle loss. This applies especially to advanced individuals and when you are not overweight.
Intermittent fasting can be a sustainable approach to work towards your goals, but it can also take you further away from your goals if it is not applied correctly or does not fit within your current lifestyle.
What you should know before starting intermittent fasting
Your body needs time to adjust
It can take several days to weeks before you are adapted to the fasting period. Ghrelin (a hormone that regulates hunger) has a fixed daily rhythm (circadian rhythm) with a trough in the morning (08:00), a peak in the evening, and a gradual decline at night.
This pattern remains the same during a fasting period of 12-84 hours. Entraining (adjusting the daily rhythm) ghrelin is possible by adjusting meal times and meal frequency [3]. Hunger signals that you normally have around 08:00 may occur later when the first meal is delayed by a few hours.
Insulin also plays an important role in your hunger’s circadian rhythm. This means that you get hungry when you normally would eat. If you want to adjust your eating rhythm, you must temporarily deal with hunger while your hunger’s circadian rhythm adapts.
So, it is especially important to form a fixed meal pattern and consistently stick to it. Otherwise, your body will be busy readjusting, resulting in fluctuating energy levels and disrupted hunger signals.
Women are better off fasting for shorter periods than men
From practice, it appears that women are more sensitive to large calorie deficits/long fasting periods and are more likely to get hungry or have less energy when following such an approach. Women who postpone their breakfast are more likely to overeat later in the day than men [4].
By completely fasting for a period of 12-72 hours, there seems to be a similar physiological and hormonal response between men and women with normal weight [5]. This means that after a prolonged fasting period, there is no significant difference in blood sugar levels, blood pressure (systolic and diastolic blood pressure), and some hormones that regulate resting metabolism.
Personal experiences play an important role in whether long fasting is sustainable or not. In general, as a woman, you don’t want to fast for more than 14 hours, while men have less trouble fasting for longer than 14 hours.
Good situations to apply intermittent fasting
An active lifestyle or not having a stable eating history do not go hand in hand with intermittent fasting. Doing office work and not needing to eat early in the day provides a better fit.
From anecdotes and research, a fasting period of 14-16 hours is generally the sweet spot to make intermittent fasting sustainable. In practice, this means delaying breakfast until around 10:00-14:00 (depending on when your last meal of the day takes place).
Irregular fasting methods like Brad Pilon’s
eat stop eat method or alternate day fasting can help with weight loss, but they prevent your body from forming a regular rhythm, which brings along some disadvantages.
Consistency is the key to success.
Example of a daily schedule An example of a daily schedule where fasting lasts for 16 hours.
Other lifestyle factors essential for making intermittent fasting successful include adequate sleep, stress management, and making ‘healthy’ food choices. Having a sleep debt, high stress levels, and making poor food choices make any diet unsustainable. Regardless of whether you do IF or not.
It can take 2 weeks to adjust to a regular IF rhythm. To make intermittent fasting successful, it’s important not to underestimate other lifestyle factors.
The conclusion about intermittent fasting
Intermittent fasting can be a good tool for losing fat, but it’s not for everyone.
This is especially true if you have an active lifestyle, don’t have a stable eating history, are a beginner in strength training, and have low appetite.
Intermittent fasting fits better when you have office work, no need to eat early, have a large appetite, regularly eat out, and are at an intermediate level or above in strength training.
From anecdotes and research, a fasting period of 14-16 hours is generally the sweet spot to make intermittent fasting sustainable. In practice, this means delaying breakfast until around 10:00-14:00 (depending on when your last meal of the day takes place). Note that it may take some time for your body to adjust to your meal pattern.
Irregular fasting can help with weight loss, but it prevents your body from forming a regular rhythm, which brings along some disadvantages such as hunger, protein synthesis, or a slowdown in resting metabolism.
Hopefully, this article has provided you with new insights into intermittent fasting.
References
- Saad A, Dalla Man C, Nandy DK, et al. Diurnal Pattern to Insulin Secretion and Insulin Action in Healthy Individuals. Diabetes. 2012;61(11):2691-2700. doi:10.2337/db11-1478.
- Am J Clin Nutr November 2009 vol. 90 no. 5 1244-1251
- Frecka JM, Mattes RD. Possible entrainment of ghrelin to habitual meal patterns in humans. Am J Physiol Gastrointest Liver Physiol. 2008 Mar;294(3):G699-707. doi: 10.1152/ajpgi.00448.2007. Epub 2008 Jan 10. PubMed PMID: 18187517.
- Halsey, L., Huber, J., Low, T., Ibeawuchi, C., Woodruff, P., & Reeves, S. (2012). Does consuming breakfast influence activity levels? An experiment into the effect of breakfast consumption on eating habits and energy expenditure. Public Health Nutrition, 15(2), 238-245. doi:10.1017/S136898001100111X
- Webber J, Macdonald IA. The cardiovascular, metabolic and hormonal changes accompanying acute starvation in men and women. Br J Nutr. 1994 Mar;71(3):437-47. PubMed PMID: 8172872.
- gezondheidsraad.nl/nl/taak-werkwijze/werkterrein/gezonde-voeding/richtlijnen-goede-voeding-2015
