Intermittent fasting is an eating pattern where one cycles between periods of eating and periods of fasting. This entails restricting energy intake to less than 75% of usual intake for 1-3 days per week and eating freely on non-restriction days. It is proposed that this type of eating pattern may have powerful benefits for your body and brain. In this blog post we discuss these claims within the context of the current evidence to determine whether this way of eating really does confer the benefits it proposes to.
Here are 5 claims made by those who promote intermittent fasting:
- Changes the function of cells, genes and hormones
- IF is reported to:
- Decrease insulin levels and increase insulin sensitivity (to help increase fat burning)
- Increase human growth hormone (to increase muscle growth) and
- Increase the cell’s ability to ‘detox’
Insulin: There are mixed results in terms of research into Intermittent fasting dietary behaviours. There are no consistent findings, as some studies show a decrease in fasting insulin levels and others show no significant change when compared to other energy restrictive diets..
Human growth hormone: It is well known that a decline in human growth hormone leads to a loss of lean body mass in the elderly and it has been established in some studies that long term fasting (>2days) may increase levels of growth hormone, but to say that fasting can increase growth hormone enough in a younger patient has not been established. In fact, various studies have shown that fasting may even increase loss of lean muscle mass and protein.
Detox: Fasting rodents have shown an enhanced concentration of an enzyme that helps to detox the liver, thus fasting has been promoted as a way to detox the human system more efficiently. Upon further animal and human studies, it was shown that fasting did not activate these enzymes but merely shrunk the liver and so in comparison to the smaller liver it seemed as though the liver enzymes had increased. Fasting actually reduces liver glutathione which assists in the excretion of drugs and is an internal antioxidant and in rodent models fasting rats were more susceptible to damage by toxins than rats in the fed state.
Weight loss occurs when your calorie intake is consistently less than your energy needs. Intermittent and energy restriction decrease the quantity of food (and thus calories) consumed and thus result in weight loss. However, study results reveal a superior decrease in body weight by calorie restriction vs Intermittent fasting with comparable reductions in belly fat mass, and Intermittent fasting may result in an increased perception of hunger and thus result in poor compliance in some.
Some studies show that Intermittent fasting in obese patients leads to an improvement in heart disease markers, however other studies show an increase in insulin resistance and LDL (less desirable) cholesterol or no significant changes during the fasting period. The effects on heart health need to be studied a lot further in humans before recommendations can be made.
Intermittent fasting has been shown to help prevent cancer in animal studies and one paper in humans showed that it might reduce side effects caused by chemotherapy, further testing is needed to determine the effects of fasting on clinical outcomes, including quality of life.
In young mice with neuro-degenerative disorders, Intermittent fasting increases the brain’s resistance to dysfunction and degeneration. This is possibly due to decreased death of new cells rather than increased production as well as an increase in protective proteins and a decrease of inflammation. Unfortunately this does not seem to be the case in older mice and human studies are yet to be conducted. What is interesting in these studies is that most studies subjected the mice to dietary restriction and not necessarily Intermittent fasting, thus proposing instead that it is calorie restriction that in fact might also be useful for brain health.
The bottom line:
We know that excessive energy intake is associated with increased incidence of heart disease, diabetes, and certain cancers. The influence of meal frequency on human health is still unclear, however Intermittent fasting has many promising applications. Remember it is early days for most of the research and as of yet it has not been proven to be superior to traditional calorie restriction. Until more studies have been done in humans, we cannot assume that benefits in animal models will result in benefits in human models… Until then we advise that you contact your dietitian at Nutritional Solutions to provide a nutritionally balanced diet to help you reach your weight goals and to rather discuss the option of using intermittent fasting regimes on an individual basis with your Dietitian’s supervision.