Fasting: Myths, Benefits, Studies, Protocols & More

I consider fasting not only a 'useful tool' in health optimization and fat loss, but an irreplaceable practice for cellular clean-up.

Remember, humans evolved through hundreds of thousands of years while practicing a range of (involuntary) fasting patterns. Clearly, we evolved to be adapted to occasional periods of not eating, sometimes longer, sometimes shorter.

Fears and myths around fasting:

• One of the most popular misconceptions about fasting is that it's a starvation mode and so it cannot be good. Studies show that catabolic processes in the skeletal muscle tissue only start after 60 hours of non-eating. What about the metabolic rate? Does it go down? Studies show that metabolic rate does NOT decrease until after 2-3 days of fasting; it may actually increase by up to 15% during short-term fasting due to stress hormones.
• Another misconception is that skipping meals will lead to blood sugar getting dangerously low. But the evidence says that healthy adults can fast without real metabolic problems; feelings of hunger are subjective and do not indicate actual hypoglycemia. (And we will talk about who should abstain from fasting as well).
• And the last myth I want to touch upon at this time is that 'fasting can create unhealthy eating patterns and lead to eating disorders'. A study on alternate-day fasting showed minimal adverse outcomes, decreased depression, and binge eating, while improving body image perception. So that's also a myth.

Let's discuss the different types of fasting, the difference between fasting and actual starvation.

It's important to note that why fasting has so many benefits, that I will talk about below as well, is because it's ultimately about calorie restriction.

Numerous studies on animals have shown that animals who eat less over their lifetime, live longer.

 Let's have a look at what some of the fasting methods are that have been researched:

• Random meal skipping. This is a natural way some people operate - just choosing to skip a meal, when they're busy, when there's no access to quality food, when they're traveling, etc.
• Alternate day fasting. This is the most researched fasting method. People eat normally one day, then fast or consume less than 500 calories the next day.
•  Time-restricted feeding. The difference here is that people do not have a complete day of fasting, but eat every day within a compressed eating window of 8 to 12 hours. 

There are obviously, a wide array of possibilities with fasting. My personal favorite is 42 to 48 hours. I used to do it quite a bit when I was actively losing fat. This is a fast where I only drink water, black coffee or tea, and don't consume any food. And why it's my favorite is because at the 42 hour mark is where I start feeling the best, having acute mental clarity and the most energy. 

So what's the difference between fasting and starvation?

Starvation is a long-term food restriction which leads to adverse health outcomes - loss of skeletal muscle, decreased metabolic rate, reproductive challenges, structural changes that can be irreversible.

In contrast, fasting is a time-limited food restriction, alternating with refeeding or so called 'feasting'. Fasting is not detrimental to health and provides numerous benefits.

And by the way, if you're concerned about regaining weight after caloric restriction, please note that short periods of fasting (as opposed to long-term 'starvation') are beneficial for fat loss and do not create conditions for weight regain.

Now that we're talking about the benefits of fasting, let's go through them.

The benefits of Fasting:

• fat loss
• blood sugar control
• autophagy (clean-up of damaged cell parts)
• improved lipid profile
• improved cognition

Controlled trials on intermittent fasting have shown the following outcomes:

• 85% of intermittent fasting trials show statistically significant weight reductions. Example: A study on overweight women comparing daily energy restriction vs. 5:2 diet (500 calories on two days per week) - both groups lost weight.
• Fasting, including the 5:2 diet, shows reductions in total cholesterol (10-21%) and triglycerides (14-42%) in normal weight, overweight, and obese people. Some studies show improvements in HDL cholesterol and triglycerides, but an increase in LDL cholesterol, which will normally go up, when a person is using fat as fuel, because LDL is actually the bus on which the fat in the bloodstream sits. So if you're transporting fat to use it for fuel, it's normal that the number of buses in the bloodstream will go up. You just need to make sure the inflammatory markers are not elevated at the same time. Cholesterol by itself is not the concern.
   

An important caveat here is that fasting for fat loss only works for daytime eating. Eating during sleep periods, i.e. when it's dark outside, can lead to negative consequences. Evidenced by higher rates of obesity, heart disease, and cancer in night shift workers.

Taking care of your circadian biology is fundamental, always. The liver's functions, such as glycogen synthesis - converting carbohydrates into a storage form (during the day) and glycogenolysis - breaking down that glycogen to use for fuel (at night), are influenced by these rhythms.

Some of the mechanisms of fasting:

1. Decreasing chronic inflammation.

Fasting is a powerful tool for slashing inflammatory biomarkers in the blood. A 2012 study during Ramadan showed a 57% decrease in IL-6 and a 71% decrease in TNF-alpha after 21 days of fasting (13-15 hours/day). Inflammation levels returned near baseline after resuming a normal diet, indicating the impact of fasting on inflammation.

2. Improved Stress Response via Heat Shock Proteins.

Interestingly, fasting increases the production of heat shock proteins by the body, and they are essential for cell survival under stressful conditions and are highly conserved across the animal kingdom.

3. Slows down the aging process. 

Fasting reduces IGF-1 (a growth factor). In one study, nineteen subjects fasted once a month for three months. After they resumed their normal diet, these subjects displayed a 15% reduction in the level of IGF-1. This suggests that fasting increases IGF-1 sensitivity, indicating that the body is functioning on less growth signal.

4. Improvement in leptin sensitivity.

People have trouble losing weight when they are leptin resistant. This condition in simple terms is the inability of the brain to receive the message on the energy balance of the body, that leptin is supposed to transmit to it. A 24-hour fast significantly improves the function of the leptin transporter at the blood-brain barrier.

Are there studies showing negative effects of fasting? 

Yes - this is how NOT to do fasting: 

1. Alternate Day Fasting Study:

•  Strict alternate day fasting for three weeks (36-hour fasts) resulted in weight loss from both fat and muscle mass.
•  Increased hunger throughout the trial.
•  Improvements in insulin sensitivity were observed in men, but not women. 

2. One Meal Per Day Study:

• Subjects eating one meal per day for two months (dinner only) had poorer blood glucose control compared to those consuming three meals per day. Again, this is too stressful, if done for too long, not only because of 1 meal a day, but the timing of that meal. 

Strict patterns like one meal per day or prolonged fasting intervals may not be ideal for long-term adherence.

Who should avoid fasting, generally: