Today there are so many different options for people to lose weight so that you don´t really know which one is the best. One of the most popular may be Intermittent Fasting (IF). Currently, you find so many blogs or articles about IF and it will be always described as the "holy grail of weight loss". You can eat what you want and more promises for people are out there, to lose weight with this diet form. But, does IF really lead to weight loss if you can eat as you do right now? Or do you need to consider more than only the time in which it is allowed to eat? For the further analysis of intermittent fasting, it is very important to consider that we only look at the most popular one: time-restricted eating. There are more IF options out there, which can lead to other effects.
In the first chapter of this article, we need to look at the process of weight loss: What is mainly needed to lose weight? Therefore, we need to look at different perspectives of weight gain, maintenance, or loss. On the one side, we have our energy intake. This consists of all food sources and beverages we consume over the day. On the other side, there is the energy expenditure. So, every calorie we burn is on this side of the scale. The energy expenditure consists the basal metabolism rate (BMR) which includes all process of our body which burn calories without any physical activity. So this amount of calories will be burnt every day independent of or physical level. There are many BMR calculator which can give you a guide value. The next calories our body burns are for digestion because this process can need a lot of energy. But it is also mainly stable between the days. The only point where you can make a difference is on the exercise side. So, if you do more physical activities, you burn obviously more calories and so shift the scale to the other side. But. mainly we want to maintain our body weight. Therefore our energy expenditure needs to be in equilibrium with the energy intake, as you see in Figure 1. But, if you want to lose weight, you need to shift this scale. Therefore, you need to consume less food or beverages, or you need to be more physically active. Or both!
Figure 1 Weight Loss (Source: https://www.researchgate.net/profile/Stefan-Du-Plessis/publication/268801743/figure/fig1/AS:295390877372432@1447438081994/Energy-balance-exists-when-energy-intake-is-equal-to-energy-expended-The-principal-cause.png; Retrieved from 16.05.20210)
So you see, for weight loss, the most important fact is, that you need to be in a negative energy balance. And here, time-restricted IF can be the solution.
Time-restricted IF allows ad libitum energy intake within specific time frames, inducing regular, extended fasting intervals (2). The main objective of IF is to achieve a negative energy balance in that way, that you have less time to consume food (1). So, IF consists of abstaining from food and caloric beverages for a certain period of time alternated with normal eating. Now, after we know what the IF actually means and how the method decrease or energy balance, we can look at other health benefits as well as the most common options of IF.
Benefits of Intermittent Fasting
Time-restricted feeding was associated with reductions in body weight, total cholesterol, TGs, glucose, insulin, interleukin 6 (IL-6), and TNF-α, as well as with improvements in insulin sensitivity - but mostly animal studies (2)
Improved oscillations in circadian clock gene expression, the reprogramming of molecular mechanisms of energy metabolism, and improved body weight regulation (2)
Gastrointestinal (Gut) Microbiota: fasting regimens appear to have positive impacts on the gut microbiota (2)
Life-style behavior: improvements in self-reported sleep satisfaction, satiety at bedtime, and energy levels (2)
Potential effects of prolonged nightly fasting on energy intake, sleep, physical activity, and circadian activity rhythm may act in concert to reduce the risks of cardiometabolic disease and cancer (2)
Options of Intermittent Fasting
16:8: This IF form may be the most popular one. You have 8 hours the day to eat and during the other 16 hours, you need to fast. The 8 hours in which you can eat, can be placed wherever you want. But, I will recommend you to skip breakfast and eat your first meal at lunchtime.
5:2: This specific method doesn´t really divide your day into a fasting and eating zone. Moreover, five days a week you can eat normally with no restriction. On the other two days, you need to fast the whole day. These days can be also placed on any day of the week. Maybe a day in which you needn´t be active at all.
Warrior Diet: The hardest and maybe the most powerful intermittent method is the warrior diet. In this form of diet, you eat only one meal per day in a time slot where you want. This meal can be as big as possible. Also, all beverages and food sources can be consumed in this meal. As I already told you, Intermittent Fasting restricted the time in which you can eat. Not the sources of what you eat.
That different options of IF are the most common ones. So there are more out there, which are not further discussed here. But, I recommend you for your beginning the 16:8 diet form (see Figure 2), because it is the easiest method. But for some individuals, one method fits better to their daily life than the other method. So maybe, try the different methods for your one and evaluate which one is the best for your daily life and metabolism.
Figure 2 16:8 Method (Source: https://i0.wp.com/images-prod.healthline.com/hlcmsresource/images/topic_centers/2020-1/250481_IntermittentFasting_body_1296x728_16-8.png?w=1155&h=1528; Retrieved from 16.05.2021)
So in the end, you see that IF can lead to weight loss and also to some other health benefits. But I recommend you to lose no more than 0,5 kilos per week.
At the end of this article, I want to summarize the most important facts you need to consider if you want to lose weight. The most obvious one is, that you need to have a negative energy balance at the end of the day. So I always recommend persons, who want t lose weight, to write a diet plan which consists of all consumed foods and beverages in the first week. So, that you first be aware of what you eat and what calories each food has. Reminder: High-calorie foods need not be bad. Healthy foods, like nuts, oil, avocados, consider for instance healthy fatty acids, which you also need to consume during your diet. But try to reduce such sources to a minimum. The next point which is very important to lose weight is, that you need to consume mainly nutritional-dense or high-quality food. So, what is meant by that? As I wrote two sentences above: High-calorie foods need not be bad. So try to eat healthy and balanced, also during your diet. That means, try to limit sources that are not necessary for your body. Also, eat food that saturates you in the long term. Such sources can be oats, potatoes, broccoli, ... And the last important fact is, that you can decrease your energy balance also by being active. So go out there and be physically active. Right now it can be also a good choice to escape from the stress in your daily life!
On Friday you will get an individual diet plan where you can add your daily calories. Also, some important diet tips for weight loss will be a part of this diet plan. So, check it out if you want to lose the last kilograms for the summer!
(1) Freire, R. (2020). Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets. Nutrition, 69, 110549.
(2) Patterson, R. E., & Sears, D. D. (2017). Metabolic effects of intermittent fasting. Annual review of nutrition, 37.
(3) Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss: Systematic review. Canadian Family Physician, 66(2), 117-125.
de Cabo, R., & Mattson, M. P. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine, 381(26), 2541-2551.