Intermittent Fasting studies have been conducted for decades. The volume of information about the dietary intervention can be confusing, but a recent academic review published in the New England Journal of Medicine (NEJM) brings much-needed clarity.
In the review, the authors analyse a proliferation of Intermittent Fasting research. Their conclusions show that there are broad health benefits of fasting that could be associated with longevity and anti-aging.
In this article, Fit4100 takes a deeper look at the findings.
What is Intermittent Fasting (also known as IF)?
Sometimes it can seem like Intermittent Fasting’s meaning is blurred because there are so many different methods recommended by various experts. Some popular examples of Intermittent Fasting techniques are the 5:2 diet, the 16/8 fasting method, and alternative-day fasting.
Because fasting can be approached in so many different ways, it’s most accurate to think of Intermittent Fasting as an umbrella term that describes a dietary intervention involving limits on when you eat.
The NEJM review authors analysed evidence on the effects of Intermittent Fasting generally – their pool of research included studies that dealt with all the versions of IF mentioned above.
What happens to the body during Intermittent Fasting?
Regardless of what specific fasting method you use, the purpose of Intermittent Fasting is to trigger a physiological process called a metabolic switch.
When food is eaten regularly and often, the body uses glucose from that food for energy. Research shows that after 8-12 hours of fasting, the body switches to a new fuel source. The liver begins to convert fatty acids into ketones and these ketones are used to power the body’s tissues – including the brain.
This change can trigger weight loss, as it allows stored fat to be burned off as energy. But, the authors of the NEJM review say that weight loss is not the most important result of metabolic switching:
“Ketone bodies are not just fuel used during periods of fasting; they are potent signaling molecules with major effects on cell and organ functions. Ketone bodies regulate the expression and activity of many proteins and molecules that are known to influence health and aging.”
This is the core of Intermittent Fasting science; when fasting occurs regularly, the metabolic switch triggers a series of positive changes in the body. Among these changes are decreases in insulin resistance and inflammation, and improvements in heart rate and blood pressure – all of which are important for reducing the risk of multiple life-shortening diseases.
What are the health benefits of Intermittent Fasting?
In the NEJM article the authors review Intermittent Fasting research and outline key proven Intermittent Fasting benefits. Below is a selection of those most relevant to longevity –
Intermittent Fasting and diabetes
Animal studies have shown that fasting can result in less obesity and insulin resistance – both risk factors for Type 2 Diabetes. Research in Okinawa, where the population typically eats in an intermittent fasting pattern, also reveals low rates of diabetes. Further information about IF and and Type 2 Diabetes can be found here.
Intermittent Fasting and cardiovascular disease
The study’s authors state that, “Intermittent fasting improves multiple indicators of cardiovascular health in animals and humans”. Among the listed benefits of fasting are positive changes in blood pressure, resting heart rate, cholesterol, glucose, and markers of systemic inflammation.
Intermittent Fasting and cancer
This is another area where human trials are in the early stages, but animal trials have shown consistent positive results from Intermittent Fasting – including reduction in the spontaneous occurrence of tumours and suppression of tumour growth. There are tentative positive signs in human studies, with multiple case studies of patients with glioblastoma suggesting that “intermittent fasting can suppress tumor growth and extend survival”.
Are there Intermittent Fasting side effects?
The article’s authors warn that “on switching to an intermittent-fasting regimen, many people will experience hunger, irritability, and a reduced ability to concentrate during periods of food restriction”.
But the article goes on to state that “these initial side effects usually disappear within 1 month”.
Anyone considering Intermittent Fasting should discuss it with their doctor before beginning. This is important for everyone, but especially relevant to those on regular medications that might require adjustment.