Fasting is a part of many cultures, mainly driven by religious practice. In Christianity, practioners give up something for Lent. Muslims have strict fasting during the month of Ramadan. I grew up in India, where fasting for a religious reasons is a way of life.  Many Hindus have a special day of the week to fast to please a particular deity. Each deity has their own designated day. Some people fast a couple of times a week. Some women fast for the wellbeing of their husbands, though I have never seen it done in reverse!

            As children, we looked forward to the grown ups days of fasting because a special breakfast of a sanctioned food would either usher in or break the fast. To this day, these are some of my favorite meals. Calorie-wise they don’t make any sense to me, as those foods are starch heavy. Now, with fasting for weight management becoming more popular, I realize that the ritualistic fasting likely served a health benefit. So even if the sanctioned foods were not “light” the prolonged period of no consumption was resetting some metabolic processes.

 

           As we all know, weight management is a multi billion-dollar industry in the United States. I have always been conscious of calorie intake and expenditure, have exercised regularly, but however much I counted calories or points or grams, or increased protein or decreased carbs, or cut out bread, weight has always been an issue.

            One day, I caught up with a scientist friend who is skeptical of fads. He told me about intermittent fasting, he had looked into the science of it and it seemed valid, and had lost a lot of weight and and had reaped many health benefits. I decided to give it a shot. My husband and I started intermittent fasting and the results have been quite satisfactory.

 

 This summer, I found a review paper on Intermittent Fasting (IF) in the New England Journal of Medicine (NEJM). It’s a comprehensive review of animal and human studies, and outlines the medical benefits of IF and the possible mechanisms.

The health benefits are not just because we eat fewer calories and can lose weight. During intermittent fasting, our metabolism switches from using liver derived glucose to ketones derived from fat tissue.

            Glucose and fatty acids are the main energy source for our cells. When we eat, glucose is used for energy, and fat is stored in fatty tissue as triglycerides. When we fast, triglycerides are mobilized from the fatty tissue and are broken down to fatty acids and glycerol. The liver breaks down the fatty acids to ketone bodies, which then provide the energy source to the cells. That’s one pathway to mobilize fat.

            What are the benefits to mobilizing ketone bodies? Ketone bodies provide important metabolic signals for proteins and molecules that influence health and aging. In addition, they stimulate the expression of the gene for brain derived neurotrophic factors. These are peptides that support the development and growth of neurons. Several studies have shown that IF improves working memory, executive function, and global cognition in people with mild impairment and obesity. More studies are obviously needed.

 

What is the effect of intermittent fasting on the adaptive stress response? It increases antioxidant defenses, DNA repair, and down regulation of inflammation. These responses enable cells to remove oxidatively damaged proteins and mitochondria and recycle undamaged molecular constituents.

 

The combination of these molecular effects have beneficial effects for multiple health conditions.

 

Diabetes Mellitus

The beneficial effects on Diabetes are seen not just because of decreased calorie intake. In a trial of intermittent fasting versus decreased calorie intake, the two groups lost the equivalent amount of weight.  But the intermittent fasting group showed increased insulin sensitivity, as well as decreased waist circumference. And as we know, it’s the belly fat that is the worst fat.

Cardiovascular health: improvement in blood pressure; resting heart rate; levels of high-density and low-density lipoprotein (HDL and LDL) cholesterol and triglycerides. In addition, intermittent fasting reduces markers of systemic inflammation and oxidative stress that are associated with atherosclerosis. The benefits are seen in normal weight and overweight adults. However the benefits dissipate when a normal diet is resumed.

Asthma showed an improvement in symptoms. A reduction in symptoms was associated with significant reductions in serum levels of markers of inflammation and oxidative stress. Other conditions which would also benefit from decreased inflammatory markers would include inflammatory arthritis, and studies have shown improvement in Rheumatoid Arthritis.

Multiple Sclerosis is an autoimmune condition which results in demyelination of axons , and neuron damage. Studies have shown reduced symptoms in as short a period as 2 months

Cancer: Animal studies have shown decreased spontaneous tumors, impaired metabolism of cancer cells and strengthening the stress resistance of normal cell. Human studies are underway, mainly to study compliance, side effects and biomarkers. No studies are available so far about the benefit of recurrence rates.

 

Does IF have negative Physical effects?: Young men on a 16 hour daily fast with ongoing resistance training were able to maintain muscle mass and lose body fat. There was a recent study published in The Journal of the American Medical Association (JAMA) that found some loss of muscle mass, but there has been criticism of the design and duration of this study.

 

What are the fasting schedules?

 

One is a daily restriction of the time frame in which you can eat, mainly to fast 16-18 hours a day, and restrict eating to an eight-hour window.

 

The second is to fast 2 non-consecutive days a week, restricting calorie intake to 500 on those days. It can be hard to jump into that, and one can work up to that schedule gradually, decreasing calorie intake on one day and then progressing to two.

            I have found the 16 hours off and 8 hours on to be the simplest for me. The 16 hours can conveniently dovetail with sleep schedules and giving up one meal, ideally dinner. But our only social meal is dinner, so I gave up breakfast. Giving up breakfast went against all my previous knowledge, that breakfast is the most important meal of the day, but I found that easier than going to bed hungry and succumbing to a late night snack.   My husband chose 2 days a week of a 24 hour fast.

            The challenge is mainly that we are socially conditioned to eat 3 meals a day and snack in between. We are bombarded with advertising from the food industry, and we socialize around food and drink.  And initially, fasting can cause hunger, irritability, reduced ability to concentrate. Previously, missing a meal caused me to be “hangry”. But keep at it because you body will get used to this and the symptoms will resolve in a month. Now, I am used to it and I do not experience “hangriness”.

            My husband and I were able to lose weight, and keep it down. I’ve found that even when noontime comes and I can have lunch, I am often busy and the 16 hours of fasting stretches to 18 hours without difficulty. I do miss breakfast foods, and sometimes I will eat them for lunch. And on weekends, when our family can have special breakfasts together, I change my schedule.  I’m careful to eat moderately in my 8 hour window, but I don’t have to constantly be a mathematician and accountant for food choices.

            It is well known that even when diets work, if they are not sustainable, then they don’t work long term. For me, I’ve found IF to be the only way of instituting long-term changes.

 

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