You may have heard about intermittent fasting, but felt afraid to try it. “Don’t eat for 24 hours” doesn’t sound like much fun. Luckily, you don’t have to begin with anything so dramatic. Scientific research shows that even 12 hours of fasting can prompt a metabolic switch that has “potential to improve body composition in overweight individuals” (1). 

Fasting has many benefits beyond weight loss. Dr. Mark Hyman calls it “a powerful tool for longevity” (2) He states that fasting repairs damaged DNA and clears away injured cells. He says that “fasting also promotes metabolic flexibility, mental clarity, and sustainable energy levels.” Plus, it’s good for anti-aging! So there are a slew of compelling reasons to make intermittent fasting part of your health and fitness regimen.

fasting benefits

Fasting for 12 hours is easier than it sounds since time asleep counts! If you sleep for 8 hours a night – and you probably should! – you can choose between at least three ways to complete your 12 consecutive hours of fasting. You can:

  • Fast for four hours before bed, or
  • Fast for four hours on waking, or
  • Split it! Fast for two hours before bed and for two hours on waking.

You may know instinctively which of these options will work best for you, but you can try each of them and then decide what feels best. A new study confirms that after 12 hours of fasting, “the body switches from glucose to fat metabolism,” thereby “regulating protein synthesis and autophagy.” It states that “these cellular responses are central to the metabolic benefits of time-restricted eating (TRE)”. (3

This means that if you adopt a daily 12:12 routine, which means 12 hours of fasting, followed by a 12 hours feeding or eating window, you are likely to improve your metabolic and overall health. 

Another benefit to using a 12-hours-feeding window followed by a 12-hours-fasting window regime is that it helps build effective habits. Once you acclimate to a 12:12 routine, its consistency will bring about an improvement in your mentality where food is concerned. You’ll know that there are specific hours where food doesn’t need to enter into your thinking. If you’re outside your feeding window, your mind will learn to occupy itself with other things!

Once this freedom-from-food-while-fasting mentality has been achieved, it will be relatively easy to shift to a 14:10 intermittent fasting plan. It seems that it is best to make small changes in your eating habits incrementally, rather thandemanding large, immediate shifts in routine.  Mark Mattson, Ph.D., author of


The Intermittent Fasting Revolution, notes in a video interview that it takes “two weeks to a month” before you manage to adapt completely to a shortened eating window  (4). He suggests that “over a period of a few months, [you] progressively narrow the time window” in which to eat each day.

Once you are ready to move on to a 14:10 schedule, the benefits will be excellent. Dr. Sarah Berry says it’s “really exciting” that even a ten-hour eating window shows positive results and improves “mood, energy levels and hunger”(5).  

After you acclimate to a 14:10 fasting:feeding routine, you may wish to consider moving to 16:8 and then 18:6, for even greater health benefits. 

When you begin an 18 hour fast, it is time to think about human growth hormone (HGH). This hormone usually declines with age, leading to decreased muscle mass and increased body fat. Studies suggest that long fasts like a 24 hour fast increase Human Growth Hormone, but it is thought that 18 hours may be enough to affect your HGH in a positive manner. Back in 2016, intermittent fasting expert Dr. Jason Fung noted, “as you fast more, your growth hormone is going to skyrocket” (6). More than 35 years ago, a classic research study confirmed a link between fasting and growth hormone, so this is not a new or unstudied finding (7). 

By the 18th hour of fasting, autophagy is also likely to have begun. Since autophagy is the process by which your body removes damaged and unnecessary parts of cells, you can say it helps to renew your cells, leading to a healthier, more energized you! The exact amount of fasting time needed for autophagy to begin varies from person to person, but most experts agree that autophagy will have started by the 18th hour of fasting.

If you fast for a full 24-hour period, according to Dr. Jason Fung, the body may begin “to switch over to burning fat for energy” (8). He notes that “fasting is the most efficient and consistent strategy to decrease insulin levels.” This is important since the phenomenon of insulin resistance, also known as impaired insulin sensitivity, occurs when “cells in your muscles, fat and liver don’t respond as they should to insuline, a hormone your pancreas makes” (9). Insulin and glucose levels go up when we eat. When we fast long enough, they eventually go down. So fasting can be an excellent approach to dealing with insulin resistance. 

Here at Pristine’s, we care about your health. Therefore, Pristine’s emphatically recommends that you consult with your medical doctor before embarking on any significant alterations in your eating habits. Our blogs are not able, nor intended, to substitute for professional, personalized medical advice. We ask that you discuss any points of interest raised in these blogs with a trusted medical professional. 

We wish you optimal health and longevity in the New Year.

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