Intermittent fasting (IF) is receiving plenty of attention in the press and is also subject to a notable amount of scientific research on its potential benefits. So should you try it?
What is Intermittent Fasting?
Essentially intermittent fasting is simply a style of eating that focuses more on when instead of what you eat, and the general goal is to spend more time every day and/or each week in a fasted stage. When you are in a fasted stage you will have lower insulin compared to a fed state where insulin will be high. There are numerous variations of this approach. Perhaps the most basic is what is called Time Restricted Eating where you fast overnight for at least 12-14 hours. Other people use a 16/8 approach – extending the overnight fast for at least 16 hours and then eating within an 8 hour window. Some people prefer whole day fasts that usually involve fasting for 24 or more hours. These longer fasts are typically undertaken 1-2 times a week or less frequently (e.g once a month). A lot of the research looks at these slightly longer fasts.
What are the Benefits of Intermittent Fasting?
Studies have demonstrated a number of benefits in fasting:
Autophagy. Fasting induces a process called autophagy – this is the primary mechanism which relates to the disposal of waste and repair of our body cells. This is mainly why it is recommended in anti-aging diets. It can help with maintaining muscle mass and offset some of the degenerative processes linked to aging.
Weight Loss. For many people the reason they try fasting is to improve body composition. Several studies have shown that intermittent fasting is associated with weight loss. Interestingly rather than losing muscle mass research shows that intermittent fasting can cause a shift in metabolism that preserves muscle. So intermittent fasting is effective for reducing fat mass and improving body composition.
The shift in metabolism from glucose to fat appears to be more significant around 18 hours of fasting, suggesting particularly benefit from occasional whole-day fasts. However if you are a daily gym goer and looking to build muscle mass then I would recommend the 16/8 approach. While burning fat for energy is great you do not want the body converting amino acids into glucose. One study found breakdown of muscle tissue was particularly significant after 16 hours . In addition I would also suggest making your evening meal before the fast rich in slow releasing protein to help maintain muscle mass. Other research suggests it may also elevate human growth hormone – again useful if you are looking to improve body composition
The good news is that short term fasting does not appear to cause a decline in metabolism either. One study found drop in metabolic rate did not happen unti 60 hours of fasting and even then it was only slightly.
Another benefit is the reduction in inflammatory markers and oxidative stress this can mean it could be useful for many inflammatory conditions. It may also help with brain health by lowering neuroinflammation.
Chronic neuroinflammation is increasingly associated with neurodegenerative diseases like Alzheimer’s and mood disorders such as depression. There also appears to be beneifits in improving insulin sensitivity which in turn may help improve body composition and facilitate weight loss as well as lower inflammation.
Should you try Intermittent Fasting?
Fasting may not be for everyone. If you already know you don’t do well going for long periods without food (hunger, irritability, low energy etc.), or if it actually makes you want to overeat later in the day, then it may not be for you. Fasting is also not recommended during pregnancy or breastfeeding. I would also not recommend it if you have adrenal fatigue.
However if you find you can easily skip breakfast then you may find fasting suits you. If you like to exercise and are looking to improve body composition then I would also recommend training in a fasted state (e.g first thing in the morning). Studies shows that exercising in a fasted state increases both lipolysis and fat oxidation rates.