Before we dive in to this hot topic, I shall begin by saying that like many other things we discuss in this blog, the answers depend on various factors and what works for someone, might be an absolutely nightmare for someone else. It’s difficult to determine iron-clad pros and cons when it comes to intermittent fasting, first and foremost because everyone has different opinions on what it even means.
Intermittent fasting (or IF) is a broad term for various eating plans, and there isn’t one single type of eating pattern that encompasses its entire meaning. Firstly, intermittent fasting is just that. Intermittent. It’s not meant as an extreme measure and is not intended to starve you. Some people even go as far to compare fasting with anorexia, which is NOT the case. Intermittent fasting can be very beneficial and when done correctly can aid in fat loss, brain function and metabolic health.
There are a few different methods: full day fasting, alternate day fasting and partial day fasting. Full day fasting is pretty self-explanatory. It means not eating for a 24 hour period, once or twice a week and eating as normal (as in, not restricting calories) the rest of the time – this strategy has been shown to help reverse or improv diabetes. Alternate day fasting is when you limit calorie intake (as low as 500) on fast-days and eat normally on non-fast days. The most popular option and the most manageable for most people is partial day fasting, where you eat within a specific time-window. This can be an 8-hour eating window with a 16-hour overnight fast, or 10 hours on and 14 hours off, or even 12 on and 12 off. It all depends what works for you and as long as it’s consistent, the body will adapt and reap the benefits.
Intermittent fasting affects different groups of people differently. It can be very effective in the overweight population due to its ability to burn fat and increase metabolism, but can be quite harmful for elite athletes who train 2-3 times daily as when you’re training that often, the body needs sustenance and energy not only to keep going, but to properly recover. Men and women respond differently as well, so it’s important to understand how your body will react before you dive in head first. More extreme versions of fasting can be harmful for women while more moderate approaches like partial fasting can actually have an anti-stress effect.
Researchers have found the benefits of IF to be numerous. Fat loss, improved brain function and increased metabolic health are among the items listed in the pro column. The fact that it’s more sustainable long-term than calorie-restricted dieting is a huge reason it’s so effective for fat loss. One study has shown that athletes that went 18 hours without food experienced a 50% increase in fat burning. IF has also been linked to increased brain function. This could be due to its ability to stimulate the release of beta hydroxybutyrate (BHB), which is a compound that inhibits the inflammasome protein complex, which increases inflammatory response in disorders like type 2 diabetes and Alzheimers.
While this is all well and good; it’s important to note that like anything else, there are dangers when it’s not done properly. One potential downside of IF is that certain protocols, especially the more extreme versions, can suppress hunger reducing hormones, ultimately resulting in a hormonal imbalance which could cause a decrease in the hunger hormone leptin that sends signals to the brain to tell us we’re full and to stop eating. Without these hormones communicating with the brain, you won’t feel full and therefore will continue eating, sometimes even resulting in binge eating; not exactly what you want if you’re trying to lose weight. A good way to prevent this is to avoid the extreme fasting protocols like full day fasting and go with a more moderate approach like partial day fasting (eating within a set hour window and fasting the rest of the time – usually overnight.) This method has actually been proven to be more effective than calorie restricted dieting as it is easier to implicate into daily life and once the body adapts, the benefits are likely to start rolling in.
Another caution is that people with high stress levels in their daily lives might run into trouble due to the possibility of increased cortisol from fasting. A study done at the University of Virginia on a group of college women showed that after fasting for 2 days, leptin levels dropped by 75% and cortisol levels increased by 50%. Increased cortisol levels activate the “fight or flight” sympathetic nervous system and can cause intense cravings for high-carb and high-sugar foods. This happens because when cortisol levels are high, the body releases more insulin, which makes your body crave more sugar to try to lower cortisol and reduce stress High cortisol levels can also incite insomnia, which is never fun. The take away from all this stress talk is that cortisol is bad. It’s a natural and very powerful hormone that does exist and is vital to many functions in our body but we don’t want excess levels of it, so being aware of how your body reacts to fasting is extremely important.
The best strategy if you want to give intermittent fasting a try is to establish healthy, consistent eating habits to get your stress and cortisol levels under control before you begin a fasting regime. Most experts agree that the best way to start with IF is by partial fasting; a manageable way to start is by using the 10 to 14-hour rule: an eating window of 10 hours followed by a 14-hour overnight fast. This shouldn’t be all too difficult since 8 or 9 hours of that 14 will be spent sleeping anyway.
Another important tip is to eat healthy whole foods when you’re not fasting. Because of the long periods spent without food, it’s tempting to want to gorge out and eat everything in sight when you’re “allowed” to. And while it’s okay and actually encouraged to eat a large intake of calories on your non-fast days, if those calories are made up of sugar and junk, you’re only going to go backwards and end up getting frustrated; thus creating a deleterious environment. IF works best when eating whole, healthy foods made up of foods high in healthy fats, high quality protein and lots of fruit and vegetables. Fasting also works best in tandem with consistent strength training, though maybe not on the same day for some people. Train hard and eat hard during non-fast days or hours and stick to the plan. But don’t be a hero. Seriously, what’s the rush? Ease yourself in and pay attention to what your body is telling you. It knows best.
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