# RKS: INTERMITTENT FASTING CULT FOR WEIGHT LOSS

A PASSERBY OR HERE-TO-STAY

RKS / 2024-2025 / Ser 6 / Blog 2

1st November 2024

INTERMITTENT FASTING ALL SET TO RULE

THE SCIENCE BEHIND

Dear Reader,
Fasting is the act of refraining from eating, and sometimes drinking. Fasting practices may have first emerged around 1,500 BC in the Vedic, Hindu and Jainism religions. Prophet Adam was the first person to ever fast in human history. It is believed that the first fasting (done by Prophet Adam) was after his descent to earth and God’s acceptance of his prayers and repentance. It is also believed that he fasted 3 days each month during the entire year; they are the 13th, 14th and 15th.
Fasting was commonly practiced in earlier times on 'holy' days to reduce the harm to plants and animals caused by harvesting and eating. Fasting has also been used for therapeutic purposes since at least the 5th century BCE. Greek physician Hippocrates recommended that patients with certain symptoms of illness abstain from food or drink. I remember vividly my father refraining from eating whenever he once in a while became sick and refused to take even a fever tablet in spite of being a medical doctor.

Obesity has in recent times become the forerunner amongst the reasons for fasting. The world record for longest fasting spell is held by 27-year-old Angus Barbieri who went 382 days without eating any food at all in 1965 and lost 125 kgs.
Fasting is opted for spiritual development, religious pursuit and for health reasons - especially for loosing excess weight. When history is analyzed, Mahatma Gandhi, however, was the first to make fasting both a spiritual and political pursuit.
Weight loss and fasting are synonymous and March 4 is observed as the World Obesity Day by WHO as a mark of concern or awakening for the 1 billion people of the world who have obesity - globesity. It would be interesting to know about how best fasting can be undertaken successfully and the science behind the recommendation.

TYPES OF FASTING

Intermittent Fasting (IF): This is the most popular dietary approach where one switches between periods of eating and restriction. IF is also referred to as Time-Restricted Eating (TRE).
Extended Fasting: In this the dieting involves restricting eating for a long period of time, typically 24 hours or more.
Alternate Day Fasting (ADF): In ADF the practice is alternating between eating and restriction days. During an eating day, one consumes the regular healthy diet and calories.
Partial Fasting: Also known as selective or modified fasting, partial fasting involves flexible eating approach that involves eliminating certain foods from the regular diet.

WAYS OF FASTING
Water Fasting: Drinking only water for a set time slot.
Juice Fasting: Entails drinking vegetable or fruit juice only for a certain specified period.
Intermittent Fasting: Partially or completely restricted intake of food and even drinking for few hours in a day or even for a few days at a time.
Partial Fasting: Certain foods or drinks such as processed foods, animal products or caffeine are eliminated from the diet for a defined time period.
Calorie Restriction: Calories are restricted for a few days every week.

BENEFITS OF FASTING
Table: Benefits of various fasting types.
Seemingly IF and extended fasting patterns are most beneficial but the latter could be more challenging to implement.

INTERMITTENT FASTING
For losing weight it is essential that carbs are no more available for day-to-day energy needs and fats are compulsated to be utilized as an alternative. The various fasting options ensure that intake of calories are restricted so that the body has no option but to utilize fats to manufacture ATP (adenosine triphosphate) - the chemical form of energy. The proof that fats are being burnt is the presence of ketone bodies in blood and urine tests. IF is most effective form of fasting for losing weight if practiced daily.
The variations in IF include:
Fasting for 12 hours: A 7 p.m. to 7 a.m. fasting (12/12 diet) can ensure release of ketone bodies - required to enable weight loss.
Fasting for 16 hours: In this 16:8 method night meal is consumed before 8 p.m., breakfast is skipped and the noon meal is the next direct food / drink consumed by 12 noon. Besides weight management, this 16/8 IF variant even benefits sugar processing by the body.
Eat-Stop-Eat (E-S-E) Diet: Refraining from food intake completely for 1 or 2 days (5:2 or 5/2 diet) in a week is the mantra for E-S-E dieting pattern. Most people follow breakfast to breakfast next day or lunch to next afternoon meal total fasting. A 24-hour fast can be challenging and may cause fatigue, headaches or irritability.
ADF: For some people, alternate day fasting means a complete avoidance of solid foods on fasting days, while other people allow up to 500 calories. On feeding days, people often choose to eat as much as they want.
Warrior Diet: This extreme form of fasting involves eating very little, usually just a few servings of raw fruit and vegetables, during a 20-hour fasting window. The eating window is usually around 4 hours (20/4 dieting) and allowance is one large meal at night. Nutrient deficiencies are possible whilst adapting a Warrior Diet of fasting.

Besides the variants described, there are also 14/10 and 18/6 subtypes in IF. If one is not aligned to skipping meals or not eating for extended periods the hunger and fatigue during the fasting spells could be challenging. Hence, it would be prudent to initiate the 12/12 plan and graduate to the optimal 16/8 best beneficial IF variety. The 16/8 method is one of the most popular and practical fasting methods for weight loss, as it’s not overly restrictive, easier to follow and allows for regular daily eating patterns.

16/8 vs 12/12 IF

For weight loss, the 12/12 IF is not as effective as the 16/8 since ketosis is not necessarily induced in every individual. Hence, 12/12 can be the stepping stone for dieters to graduate to the more beneficial 16/8 IF variant.

16/8 vs 18/6 IF

First, the meaning of that seemingly insignificant two-hour difference can be important for how many calories one consumes. If overweight and the main goal with IF is to lose weight, having two fewer hours to eat every day can ultimately lead to fewer calories intake every day, which can add up significantly over time. However, the risk is if an individual tends to get hungry easily or if the fasting is mentally challenging, getting two extra hours to eat in a day might make a big difference in how sustainable IF will be.
An eight-hour eating window isn’t actually that different from the way one might already be eating in day-to-day life and hence, 16/8 variant of IF is more practical besides being the best beneficial.

16/8 vs 14/10 IF

Inducing ketosis is the objective of IF and a 12-hour fast could be successful in a few but even a 14-hour TRE cannot ensure the formation of ketone bodies and burning of fats.

Fig: Burning of fats vs hours of fasting.

In those individuals who have difficult in graduating to the 16/8 mode of IF the gradual stepping stones could be 12/12 followed by 14/10 before adapting the 16 hours fasting spell variant of TRE.

16/8 IF: THE SCIENCE BEHIND

Periodic fasting triggers the same fat-burning process that occurs during a low-carbohydrate or keto diet. Keto is short for ketosis, the metabolic process that kicks in when the body runs out of glucose (its preferred energy source) and starts burning stored fat. The body's scale tips towards ketosis at 12 hours and ketone bodies could appear in some after 14 hours. However, ensured ketosis is ideally after minimum of 16 hours of fasting (16/8 IF).

A keto diet achieves the same outcome in terms of weight reduction and even maintains the ketosis for much longer time periods because carbohydrates (carbs) are being consciously avoided. However, in keto diet since low carbs diet is the norm throughout the period of dieting the consumption of fats as a replacement in diet could prove to be hard for the heart in terms of excess cholesterol and triglyceride consumption.

INSULIN MFG. & SECRETION

Insulin is a hormone liberated from pancreas whenever carbs consumed add glucose to the existing sugar levels in blood. The primary function of insulin is to ensure transportation of the glucose that has entered to muscles, brain, liver and various cells of the body for energy and storage purposes. The aim of the insulin is to maintain a constant normal range of blood glucose (70-110 mg/mL) and if this action is compromized due to any reason the same is referred to as insulin resistance. It is this diminished sensitivity to the action of insulin by the target body parts that ultimately results in constant higher blood levels which is labelled as type 2 diabetes mellitus (T2DM).

Facts about insulin:

The pancreas secretes 0.25-1.5 units of insulin per hour daily during the fasting spells.
The secreted insulin occurs in cycles of every 50-150 minutes with minor fluctuations being documented every 8-15 minutes.
More than half of the daily production of 45 units of insulin by pancreas occurs during the fasting periods.
The liver first processes the manufactured insulin and allows only 22 units to be released in blood over 24 hours.
Hence, following meals the total of 11 units of insulin is available each day to take away the sugar acquired in blood via the consumed carbs in food.
For the working of insulin, as described, it takes 1-1.5 hours to transport all the excess glucose after each eating spell.
The half-life of insulin is a mere 5 minutes meaning that every 5 minutes the insulin concentration halves till it is completely removed.
It takes 1 hour to degrade any secreted insulin.

INSULIN RESISTANCE & OBESITY

There is a vicious cycle of obesity - pre-diabetes - obesity.

Obesity affects the ability of insulin to dispose off the glucose in blood after a meal - insulin resistance.
Pancreas then produce more insulin thinking that the ongoing production is not enough in transporting ALL the EXCESS glucose in blood into muscles and brain (primarily) - hyperinsulinemia.
Excess insulin in blood facilitates more accumulation of fats in adipose (fatty) tissue in body (abdomen, buttocks, cheeks) - harbinger of obesity.

The normal insulin levels range between 5-15 mU/mL fasting. If the concentration is >9 mU/mL it is labelled as pre-diabetic and in T2DM the concentrations exceed 15 mU/mL.

IF & OBESITY

It is interesting to assess the influence of 16/8 IF on weight loss.

Graph: Weight loss reported in 147 obese individuals following 16/8 IF over a lifetime.

[Cereus 2023; 15(2):e34722]

85% of those who follow the 16/8 IF plan are satisfied with their overall outcomes. The IF works best if exercising is also undertaken as a part of daily routine so as to expedite and enhance breakdown of fats and thereby ensure the weight loss more assuredly. It needs to be noted that nearly one-third of the respondents in the above-mentioned study were not exercising.

IF & INSULIN RESISTANCE

IF can lower fasting insulin concentrations by an average of 13.25 mU/L. This is significant bearing in mind that pioglitazone, the only famed insulin sensitizer drug available, can decrease fasting insulin levels by 7.9 mU/L. [Koenen TB et al. Journal of Clinical Endocrinology & Metabolism 2009; 94(11): 4453-4457]

WHY 16/8 IF IS MOST APPROPRIATE SCIENTIFICALLY?

Fasting for at least 16 hours gives the body a chance to rest and allows blood levels of insulin to drop significantly. The reasoning behind this calculation is as follows:

It takes a minimum of 10 hours for the food to be completely digested. Digestion means the food constituents - proteins, fats and carbs (macronutrients) are broken down to smallest molecular particles (like amino acids from proteins and glucose from carbs) inside the cavity of small intestine.
The absorption, namely entry from within the cavity of small intestine and exit into the blood process also requires time. (No absorption of macronutrients occurs from the large intestine) Usually the small intestine absorbs glucose at a rate of around 120 gms per hour.
The Indian diet usually contains ~350-420 gms of carbs (65-70% content of a 2,200-2,400 Kcal daily diet) and hence, the absorption time would be 3-3.5 hours.
Thus, insulin continues to be secreted until 10+3.5=13.5 hours and its levels persist for another 1.5 hours since this is the time taken for its effect in evacuating the glucose from the blood. After the action is over, the excess insulin present (since more secreted after any food intake) takes an hour for complete degradation and re-establishing the fasting normal insulin concentrations. Thus, 13.5+1.5+1=16 hours is the bare minimum time required for insulin levels to normalize and blood glucose to reach the normal range.

If IF is initiated with a 16/8 pattern, the previous meal glucose is completely utilized by 14 hours or so and the fats burning then becomes initiated such that the body's ATP requirements are fulfilled.

For reversing insulin resistance, however, a 36 hours to 3 days fasting spell is more or less essential initially to kickstart the process. This is because complete digestion of already once consumed food takes anywhere between 24 to 72 hours and hence the glucose continues to pour the blood for upto 3 days.

CONCLUSIONS

52% of consumers in the world would like to reduce their weight. There are various ways to manage weight loss:
Track diet vs exercising
Eat mindfully
Consume protein with meals
Cut down on carbs
Fill the stomach with fibre
Balance the gut friendly bacteria - especially Lactobacillus reuteri
Ensure a good 5-7 hours sleep at night
Burst stress levels with Yoga
IF
IF can be a powerful tool for weight loss and improving health, and it can be easy to fit into one's lifestyle. The Academy of Nutrition and Dietetics recommends trying to limit weight loss to one or two pounds (approximately 0.5-1 kg) per week. Typically, with IF, one can expect to lose around 0.5 to 1 kg per week, which might not seem like much, but over time it adds up to significant changes.
When one undertakes fasting, the cells in of body start a cellular waste removal process called autophagy. In this process, the cells break down and metabolize broken and dysfunctional proteins that build up inside them over time. Increased autophagy may provide protection against several diseases, including cancer and neurodegenerative diseases such as Alzheimer’s disease. IF increases the production of a protein in the brain called brain-derived neurotrophic factor, which stimulates the production of new neurons (nerve cells) in the brain. As a result, IF can lead to improved concentration, better memory and even boost energy levels.
Hence IF, especially the best adherable 16/8 plan, can never be in vain. Even a 13% increase in lifespan has been postulated as a result of indulgence in IF.
The mantra for weight loss is not only aimless dieting but adopting the 16/8 IF plan coupled with exercising. Only then will the weight loss provide bonus in terms of reducing insulin resistance, decreasing risk of heart disease and improved brain cognitive functioning as well as promising a longer lifespan and a more energetic living.

DR R K SANGHAVI
Prophesied Enabler
Experience & Expertise: Clinician & Healthcare Industry Adviser

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Dr R K Sanghavi