There has been much recent interest in the use of “fasting” as an eating strategy, either to be healthier, lose weight or even live longer. Fasting in its literal sense refers to total abstention from eating, i.e. zero calories, however, some “fasts” do allow for a small amount of calories to be consumed. There are therefore various forms of fasting.
Fasting might be popular now but it is not a new concept. In humans, much of our understanding of the effects of fasting have come from observations of religious practices (e.g. Ramadan) or individual protests (e.g. hunger strikes) or as a consequence of natural and man-made disasters, brought about by drought, famine and/or war. Coupled to this there has been a wealth of experimental insect, invertebrate and animal studies and a more recent array of human intervention trials. This body of research gives us academics a sound understanding of some reported effects both favourable and favourable.
"The cumulative recent interest in fasting mainly stems from seminal work in the 1930s on rodents that demonstrated that energy (calorie) restricting animals leads to a longer lifespan in those animals, compared to those able to eat freely."
The cumulative recent interest in fasting mainly stems from seminal work in the 1930s on rodents that demonstrated that energy (calorie) restricting animals leads to a longer lifespan in those animals, compared to those able to eat freely. This was reinforced through observations in other species, and provided the basis for the hypothesis that energy restriction can relate to greater longevity. Indeed, longevity as a discipline has emerged from this fundamental hypothesis and supports the notion of fasting as benefiting all species, specifically humans.
“When looking across a whole week, “intermittent fasting” causes people to typically eat less calories overall even when eating anything they like during non-fast days or times.”
Practically speaking fasting manifests as individuals undertaking periods of intermittent fasting, interspersed with periods of non-fasting or free (ad libitum) eating. In this way, you are gaining from the beneficial effects of fasting without actually being in prolonged energy restriction or starvation. The obvious inherent feature of fasting is the restriction of energy (calories), which can give rise to beneficial effects in terms of reduced body fat and weight loss. This may still be the case even if only fasting for brief periods (i.e. 2-3 days a week or a certain number of hours per day). Indeed, when looking across a whole week, “intermittent fasting” causes people to typically eat less calories overall even when eating anything they like during non-fast days or times. This has made intermittent fasting a popular weight loss diet, popularised by the 5:2 or fast diet.
Nevertheless, there are other distinct features of intermittent fasting that can also elicit other distinct metabolic and behavioural advantages which makes it a dietary intervention of interest beyond simply weight loss.
This will be explored in more detail during our talk at The Lab where I’ll be joined by Form CEO Damian Soong and Max Lowery, author of 2 Meal Day. I hope this talk will give you a great perspective on fasting from my own academic research through to practical applications from Damian and Max. I hope to see you there!
Dr. Adam Collins
Head of Nutrition | Form