Intermittent fasting in the latest scientific studies

The nutrition concept based on the rules of intermittent fasting has almost revolutionized the approach to eating. Although, this strategy, in reference to the fitness ideas and bodybuilding dogmas on healthy diet occurred to be extravagant, it has gained wide range of the followers among people doing resistance training, as well as those, who want to improve their body composition. The enthusiasts of intermittent fasting have enjoyed destroying the “nutrition myths” on the basis of scientific studies. But does science really support this controversial idea?

What is 'intermittent fasting' and how does it look in practice?

The phrase of 'intermittent fasting' (IF) is used for nutrition solutions, which assume introducing short-term starvation lasting from 14 to 24 hours. In practice, there are two main schemes, which apply for this concept. The first one assumes introducing complete fasting or modified one on chosen days of the weeks. The other is based on everyday fasting, but only for some part of the day.


The example of the first solution may be the dietetic strategy called ADF (alternate-day fasting), later transformed into ADMF (alternate-day modified fasting). It was prepared by Krista Varada and means that the total (ADF) or partial (ADMF) fasting is introduced every other day, alternately with the diet without any dietetic limits. It's good to mention here, that the ADF option assumes the possibility of delivering about 25% of the daily energetic demand in a form of one meal eaten before noon.


The example of the other solution may be the scheme called “leangains” and it assumes consuming the whole amount of calories in the “shortened eating window”, which usually lasts 8 hours (in everyday practice the eating window has been often shortened to 4-6 hours). This option was welcome much better by physically active people, including sports people doing shape sports, despite the fact that it hasn't been evaluated in research that often.

Intermittent fasting and overthrowing the myths

The concept of 'intermittent fasting', in reference to the current rules of healthy eating (especially referring to the fitness ideas and bodybuilding guidelines concerning how a diet should look), seems quite exotic. This idea, in its assumptions, neglects the meaning of the aspects, such as:

  • the necessity of eating breakfast,

  • high frequency of eating meals,

  • the limit of eating protein per meal,

  • the necessity of eating meals at steady time,

  • many more.

What's interesting, the enthusiasts of diets based on the concept of 'intermittent fasting' have been able to question the established dogmas and support their thesis with scientific studies, which didn't even confirm the 'theories' presented by them in a direct way. They were just able to discredit the validity of the present nutrition guidelines. The results of research done by Solaros from the SFD forum supply quite interesting data in this matter (it's definitely one of the most interesting sets of studies on IF). You can find the link to it below: (in Polish)

People, who are interested in extending the knowledge about IF, are advised to read the following: – this article informs about the basics on which the dietary solutions inspired by the concept of intermittent fasting are formed, – a practical guide concerning the aspects of introducing intermittent fasting in life,

Intermittent fasting: advantages and controversies – an article written by Łukasz Kowalski, which refers to some interesting aspects of using IF based on research.

The problems with the analysis of scientific studies results

Gathering, selecting and analysing the results of scientific studies is not that easy, and it requires knowledge, experience, as well as impartiality. It's important, in such process, to look for truth, not the “right” things. In other case, it would be easy to follow the one-sided selection of data, which would mean neglecting the publications, which do not support the thesis we want to prove. Such attitude is called “cherry picking” and is widely used on the forums, blogs and social networking sites by the followers or enemies of some particular nutrition concept, or any other idea. Fortunately, there are also more independent reviews, based on properly standarised methodology, which refer to particular dependency. What's important – intermittent fasting has been verified this way, and the conclusions are really worth citing.

An interesting survey

Although the concept of intermittent fasting may seem exotic and modern, it's worth to notice that there were quite a lot of scientific studies before it was used. Majority of them refers to the influence on the body composition, to be precise – the tempo of losing fatty tissue. The changes in the levels of the risk factors of developing circulatory system diseases or type 2 diabetes were also assessed. In the systematic survey published at the end of the previous year, scientists – Seimon, took a closer look at the results of research which compared the influence of diet based on intermittent fasting and diets based on conventional approach on the reduction of fatty tissue.

What did they find out?

The results of the analyses were following:

  • dietetic solutions based on intermittent fasting are efficient concerning the reduction of fatty tissue, but their effectiveness is close to the effectiveness of traditional nutrition solutions, which assume constant energetic restriction,

  • the influence of intermittent fasting and the conventional slimming diets on the level of muscle tissue is also similar,

  • the influence of intermittent fasting and the traditional reduction diets is similar concerning the insulin sensitivity and the glucose homeostasis,

  • so far, there is insufficient amount of data in order to claim if there are any significant differences in the influence of conventional reduction diets and diets based on the IF model on the level of the following: thyroid hormones, cortisol, leptin, sex hormones and IGF-1.

You can read the summary of the whole article if you click on the link below:

What else should we know about?

For sure, it's good to underline that in the publication linked above there was majority of studies, in which they used IF with total or modified fasting on the chosen days of the week. It's not used in practice by active people. In the fitness world, the solutions with everyday fasting just for some part of the day are used much more often, and there aren't many studies with the use of such version of IF (unless you concern the studies, in which the changes of particular parameters were observed among the Muslim sports people during Ramadan, but they were not taken under consideration in the study mentioned above). In the work cited above, the results of research in which the volunteers took up the physical activity, or did resistance training, were also omitted. The reason is quite trivial – there is insufficient amount of such studies.


Although the cited conclusions from the cited analyses don't have to be totally adequate to the reality of the “fitness world”, in which diets based on intermittent fasting are used, the study may still be useful in this context. The information found in it gives some kind of picture of the influence of IF on the body. For the enthusiasts of this nutrition concept, the fact that the cited results question the unwritten belief that intermittent fasting is the 'Holy Graal of dietetics', may be very interesting. On the other hand, you should have on your mind that, according to the authors of the publication, diets based on intermittent fasting may be an efficient tool in the work on the shape. It's worth noting, because the sceptics have tried to convince others, that “it has no right to work”. This approach presents far more optimistic conclusions.