Effects of intermittent fasting on body composition and clinical health markers
Jason Loera (March 13, 2018)
Overconsumption of foods is highly prevalent in modern culture — namely western culture. Restricting calories has been recommended for the general public for some time, but the effects have yet to be deemed successful. Rather than addressing the epidemic from a calories in vs calories out perspective, we may need to address this from a hormonal perspective. The long-lasting outcomes of over-consuming has ultimately led to a hormonal imbalance — specifically insulin — resulting in higher rates of obesity which can lead to other health-related issues such as cardiovascular disease and diabetes mellitus. There has been a common association between these kinds of diseases and medicinal interventions, but not all medicines show promising results. To reiterate, from a dietary standpoint, caloric restriction diets seem to fall short when prescribed to overweight individuals due to the lack in compliancy. In other words, it is difficult to prescribe across large populations. Fortunately, emerging research has been pointing to a forgotten, yet successful, intervention that is referred to as intermittent fasting. Recent publications have indicated several successful outcomes simply due to hormonal reestablishment.
Classification and Usage
Intermittent fasting (IF) is a time restricted eating pattern — “a controlled voluntary abstinence of food for many different reasons” (Fung, 2018). Intermittent fasting is a broad term that encompasses a variety of protocols that manipulate the timing of eating occasions by utilizing short-term daily, or alternate-day, fasts in order to improve body composition and overall health. Recent publications have shown how effective this eating regimen is for weight loss, but there has also been other profound benefits when prophylactic intermittent fasting is introduced. In general, there has been a wide array of studies that indicate positive disease-preventative measures that include altered fat metabolism, increases in HDL, adipocyte thermogenesis, neurogenesis and improved neuroprotective properties, and increased lifespan (Tinsley, La Bounty, 2015; Mattson, Wenzhen, Zhihong, 2003). These findings are largely based on short-term animal studies, indicating an area of research that could use some improvements within this eating pattern. To say the least, IF takes advantage of your daily caloric restriction’s positive effects without the negative side effects — a seemingly unrealistic outcome for most common diets that are used today.
In order to be classified as intermittent fasting, two separate time frames, or windows, need to be established — a fasting window and an eating window. During the fasting phase, energy consumption is limited to zero calories while the eating phase is usually standardized using ad libitum feeding — although some controlled groups indicate more improvements in biomarkers.
What Is the Cost?
Fasting has been used throughout human history for centuries, which can give us a real sense of what is required to adopt this lifestyle. If all that is being modified is the timing of energy consumption, then IF would be considered “free” in a sense, although opportunity cost comes into play. In fact, some people report saving money on this diet simply because it indirectly leads to fewer calories consumed, depending on the individual. With the exception of water, which is considered as one of the only ingested substance allowed, there is still a recommended supplement that can be used during the fasting phase — black coffee.
A cup of black coffee contains, at most, about two calories on average. Although no calories should be consumed during the fasting phase, this amount of energy will not hinder the fasting results significantly — assuming these calories will be used up almost immediately after ingestion. The reason black coffee is suggested during the fasting phase is due to its appetite-suppressing effects. Those who find difficulty fasting for long periods of time may find that black coffee ingestion is useful in succeeding a fasting period.
In addition to its appetite suppressing effects, there are also a few possible benefits in consuming black coffee while fasting. There has been an association of benefits between ingestion of coffee and prevention of impaired glucose tolerance-related diseases, but some studies are found to be biased towards groups that ingest caffeinated or non-caffeinated coffee.
A study aimed to investigate the metabolic effects and the rate of substrate utilization in both normal weight and obese groups. (Acheson, Zahorska-Markiewicz, Pittet, Anantharaman, & Jéquier, 1980). According to the Department of Nutrition, “Metabolic rate increased significantly in both groups; however, significant increases in fat oxidation were only observed in the control group” (Acheson, 1980). This study concluded that caffeine within coffee stimulates metabolic rate for either individual, but at a higher rate for normal weight individuals. To say the least, fat oxidation can be sped up without significantly altering plasma glucose, insulin, or carbohydrate oxidation by implementing coffee into the mix. Although this may go against what can be accomplished during a water only fast, this study did not include whether the coffee was black or sweetened.
Another study that was done recently underwent a more specific approach, focusing more on the effects of glucose metabolism and consumption of caffeinated and decaffeinated instant coffee (Keizo et al., 2012). The purpose of the study was to observe the changes in insulin between caffeinated, decaffeinated, and non-coffee drinkers over the span of 16 weeks. “The caffeinated coffee group showed statistically significant decreases in the 2-hour concentrations and the area under the curve of glucose while neither decaffeinated coffee nor [non-]coffee group showed such a change.” After waist circumference changes were measured, “caffeinated and decaffeinated coffee consumption were associated with a modest decrease in the postload glucose levels” (Keizo et al., 2012). This leaves implications of impaired glucose tolerance-protective mechanisms associated with the consumption of both caffeinated and decaffeinated coffee.
One other study observed the difference between decaffeinated, regular (containing caffeine) or regular with sugar) or water (with or without sugar). Comparisons were focused on the effects of the beverages on glucose metabolism and incretin parameters — a commonly measured biomarker when observing the mechanisms behind fasting. (Reis et al., 2018). The results show that, “Insulin sensitivity was higher with decaffeinated coffee than with water,” while, “Regular coffee with sugar did not significantly affect glucose, insulin, C-peptide and incretin hormones, compared with water with sugar” (Reis et al., 2018). Conclusions stated that, “the consumption of decaffeinated coffee improves insulin sensitivity without changing incretin hormones levels. There was no short-term adverse effect on glucose homoeostasis, after an oral glucose challenge, attributable to the consumption of regular coffee with sugar” (Reis et al. 2018). This means that coffee, with or without added sugar, does not negatively affect the fasted state.
At first, it was unclear if it was the caffeine or the coffee that inextricably improved insulin sensitivity. In modern use, fasting is mainly used for improvements within glucose metabolism, resulting in other indirect benefits that improve other health biomarkers. If both caffeinated and decaffeinated coffee consumption is shown to increase insulin sensitivity, then coffee in general may help speed the process of reversing tolerance to glucose, which the body undergoes during a fasting period. In other words, this can provide the individual with quicker results in reducing fat. Although this seems plausible to say the least, coffee with added sugar was still shown to affect glucose levels, but not as significantly as regular black coffee. With that said, it is recommended that black coffee with no added sugar is ingested during the fasting phase.
The most common place to purchase coffee is usually provided by coffee shops such as Starbucks, causing regular customers to spend anywhere between $3.00-$5.00 on average daily for black coffee. If you were to stick with this consistently, these regular visits can add up to ~$1,095-$1,825 per year. If your coffee were to be purchased separately in bulk-fashion, it can range anywhere from as little as $3.00-$13.00 for a pack, which can last you anywhere from weeks to months, depending on which brand, size, and type of coffee that is purchased. The most commonly purchased coffee will either come in the form of ground coffee, whole bean, or instant coffee. Walmart’s Folgers ground coffee is priced at ~$11.68 for 48 ounces., which allows for 380 6-ounce cup servings. This means it can provide 127–380 days-worth for less than $12.00, depending on the amount you decide to consume per day. Starbuck’s French Roast Dark Whole Bean Coffee 12-ounce bag can be purchased at ~$13.76 at Walmart — a bit more expensive than ground coffee. This bag will provide ~23–69 cups. One other commonly used coffee is instant coffee, a more convenient way of serving coffee. Nescafe Clasico Instant Coffee 10.5-ounce jar is priced at ~$7.72 at Walmart. This jar provides ~53–158 cups. If one cup of coffee were to be consumed each day, this would average to ~$17.76 per year. Overall, supplementing with coffee isn’t as costly as most supplements that are sold for similar health-improving purposes. It is fairly cheap to say the least but is not a necessity when undergoing intermittent fasting.
What Is the Dose/Timing?
There is, what seems to be, infinite flexibility to approaching intermittent fasting (IF). The most common approach includes a 16-hour fast followed by an eight-hour eating window. Some go as far as 20 to 24-hours, but the most common approach that creates more compliancy appears to be within the 16-hour range. Another common approach may also be alternate-day fasting (ADF), where the individual undergoes either a 24-hour fast followed by a “refeed” day, or it can be accomplished by completing two consecutive days of fasting followed by five days of regular dieting; this allows for the individual to compensate for the deficit in calories throughout the week, allowing for the individual to maintain their weight, or it can create an easier method in keeping calories to a minimum depending on the individuals goals. Although the goal of weight maintenance may be counterintuitive to the purpose of this diet, there has been suggestive evidence indicating a variety of benefits that may come from the intermittency of fasting itself that are also seen throughout calorie restriction. In other words, there is no one-size fits all approach to intermittent fasting, but instead, allows the individual to choose which best fits them based off of their own goals.
In general, the intent of prescribing this eating pattern is to reach a solution for obesity and many other health-related diseases. If intermittent fasting can be proven effective, this eating pattern can offer a nonpharmacological approach for improving overall health in large populations at no cost.
It has been well observed that caloric restriction can lead to many beneficial health effects on metabolic health. Numerous studies have observed that a calorie restriction of 30 to 60 percent of ad libitum intake increases the life span by similar amounts across organisms including yeast, roundworms and rodents, while simultaneously decreasing or delaying the occurrence of age related diseases such as numerous cancers (including lymphomas, breast and prostate cancers), hypertension, stroke, diabetes, neuropathy, autoimmune disorders and other risks factors for cardiovascular disease (Weindruch, 1997; Mattson, 2003). On that note, emerging research has hypothesized that these beneficial health effects can be mimicked by alternating periods of short-term fasting with periods of refeeding, without deliberately altering the total caloric intake. In other words, time restricted feeding, or intermittent fasting, may be used as an alternate method to a caloric restriction diet — a difficult diet to successfully maintain long-term.
In general, the benefits of caloric restriction have already been established. With the acknowledgement that not many human trials have undergone such observations, there appears to be very identical effects liked to time-restricted feeding, or intermittent fasting (IF) and energy-restricted feeding, or caloric restriction (CR) amongst animal studies. If studies have already observed beneficial metabolic parameters by restricting calories, and if intermittent fasting has the potential to place the individual in a caloric deficit, then those same mechanisms behind a regular CR diet should be seen across those who undergo an intermittent fasting protocol as well.
Intermittent Fasting Disassociates from Calorie Restriction
One study’s objective was to discover an alternative to achieve the benefits of a caloric restriction diet but for long-term maintenance. The study compared an alternate-day fasting (ADF) group and an ad libitum group — both of which included only mice. The ADF group required the mice to restrict all energy for two days out of the week, followed by refeeding days. Interestingly, the ADF group was able to compensate for the caloric deficit, caused by the two days of fasting, by increasing their intake by twofold on feast days. From a conclusive measure, this essentially placed the ADF group at the same number of calories that the ad libitum group consumed during the same 48 hours that the ADF group fasted, thus keeping the caloric intake the same across both groups (Anson et al., 2003). Food intake did not decrease between both groups, and although both groups maintained the same body weight, Anson (2003) concluded that, “intermittent fasting resulted in beneficial effects that met or exceeded those of caloric restriction including reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxicity stress” (Anson et al., 2003). Interestingly, this provides implications of similar, if not greater, benefits of a modified lifestyle that may showcase a more compliant method to achieve the benefits of a typical caloric restriction diet.
It is important to note that the effectiveness of intermittent fasting is largely dependent on the duration of the fast as well as the number of calories consumed both prior and after each fast. Gathering this data implies that it is the “intermittency” of fasting that allows for some of the benefits that have so far been observed. On that note, if IF is performed carefully under a systemic protocol, it can take full advantage of a caloric restriction diet and reap only the positive benefits without the negative side effects that come along with caloric restriction diets.
The health benefits of intermittent fasting have so far been consistent in most subsequent trials. Although body composition is the most common incentive for intermittent fasting, emerging research points to other metabolic improvements that may provide further incentive. Evidence under time restricted feeding has shown a more effective long-term fat loss approach from a newly discovered gut-microbiota-driven mechanism responsible for activating adipose tissue browning. IF has also been shown to improve cardiovascular health, improve insulin sensitivity, decrease neurodegenerative diseases, and reduce the risks of cancer.
Adaptive Thermogenesis in Adipocytes
There are two well-known types of fat found in humans and other mammals: brown adipose tissue and white adipose tissue. In recent years, it has been of great interest to induce thermogenic effects on the conversion of the two fats — a preferred target for increasing energy expenditure in humans and treating obesity-related diseases. “In addition to classical brown adipose tissue, the last few years have seen great advances in our understanding of inducible thermogenic adipose tissue, also referred to as beige fat” (Wu, Cohen, Spiegelman, 2013). In recent years, there has been indications for new therapeutic methods that include cold therapy, exercise, and socializing (Sidossis, Kajimura, 2015). A more recent study is also suggesting that mild stresses — particularly cortisol spikes — can also induce this process but was only performed using five volunteers, indicating that further studies should be assessed (Robinson, Law, Symonds, Budge, 2016).
A new method in recent studies points to a new gut-microbiota-driven mechanism found for activating adipose tissue browning with the use of every-other-day intermittent fasting. The study showed that, “an every-other-day fasting (EODF) regimen selectively stimulates beige fat development within white adipose tissue and dramatically ameliorates obesity, insulin resistance, and hepatic steatosis. EODF treatment results in a shift in the gut microbiota composition leading to elevation of the fermentation products acetate and lactate and to the selective upregulation of monocarboxylate transporter 1 expression in beige cells.” (Li et al., 2017).
One other study added that, “IF-induced metabolic benefits require fasting-mediated increases of vascular endothelial growth factor (VEGF) expression in white adipose tissue (WAT). Furthermore, periodic adipose-VEGF overexpression could recapitulate the metabolic improvement of IF in non-fasted animals. Importantly, fasting and adipose-VEGF induce alternative activation of adipose macrophage, which is critical for thermogenesis” (Kim et al., 2017). In general, this study reveals a mechanism of an IF-mediated metabolic benefit and suggests that isocaloric IF can be a preventive and therapeutic approach against obesity and metabolic disorders. Fasting is a stress to the body, and cortisol increases as a response to the stress. Intermittent fasting may increase the chances of inducing adaptive thermogenesis in adipocytes.
Cardiovascular Health: Animal Trials
Improvements on cardiovascular health was observed throughout four studies using rodents. In general, the rats maintained on an alternate-day fasting regimen lost bodyweight and displayed reduced blood pressure and heart rate, and improved insulin sensitivity, compared to rats that were fed ad libitum (Wan, Camandola, Mattson, 2003a; Wan, Camandola, Mattson, 2003b; Mager, 2006). Another study stated, “we provide evidence for involvement of mitogen activated protein kinases (MAPK) cascade in mediating the effects of IF as there is reduction in the expression of p38 which gets induced under diabetic condition. This was further accompanied by the concomitant decrease in cleavage of caspase3 and p53 expression” (Tikoo, Tripathi, Kabra, Sharma, Gaikwad, 2007). In addition, the diabetic rats showed improvements in the onset of hypertension. Since there was a reduced blood pressure shown in diabetic rats, the data suggests that alternate-day fasting can have a preventive effect on the progression of diabetes nephropathy.
Cardiovascular Health: Human Trials
In humans, studies are limited and not conclusive enough due to the length of them. With that said, there was a study that involved whole-day fasting trials that lasted 12 to 24 weeks. Results showed a reduction in body weight (~3%-9%) and body fat (~3–5.5 kg), and improvement in blood lipids (~5%-20% reduction in total cholesterol and ≈17%-50% reduction in triglycerides) (Tinsley, Bounty, 2015). Overall, we can see clear evidence of moderate improvements in cardiovascular health. Although the number of subjects in human trials are low, there is an observable group of humans that can provide a more accurate insight on the cardiovascular health benefits of IF.
Ramadan fasting is very common in Islam. During the holy month of Ramadan, Muslims restrain from fluid and food intake during daytime for the whole month. Worldwide, there are more than one billion Muslims, of whom the majority fast annually. During observational Ramadan observational studies, most were done using randomized controlled trials, thus creating unreliable conclusions. Furthermore, the studies were generally of poor study design with few participants and lacked control groups. As a result, the studies are highly inconclusive with the effects on body weight and blood lipids with some studies showing unchanged body weight (Meckel, Ismaeel, Eliakim, 2007; Aksungar, Topkaya, Akyildiz, 2007), while others show successful weight loss (Subhan, Siddiqui, Khan, Sabir, 2006). Therefore, no objective conclusions could be made about short-term intermittent fasting and cardiovascular and metabolic risk factors, and further, more controlled research should be done.
Glucose Metabolism: Animal Trials
In rodents, increased insulin sensitivity has been demonstrated on alternate-day fasts both with (Arumugam, Phillips, Cheng, 2010; Wan, Camandola, Mattson, 2003; Wan et al., 2010) and without (Anson et al., 2003) decreased calorie intake. Anson concluded that IF in mice disassociates itself from caloric restriction since the mice consumed the same amount of food in a 48-hour period on an alternate-day fasting regimen as mice fed ad libitum, resulting in decreased glucose and insulin concentrations that were similar to the mice on daily calorie restriction despite maintained energy intake and body weight (Anson et al., 2003). In another study, as little as two 24 hour fasts per week, without calorie reduction overall, were sufficient to improve insulin sensitivity in mice (Thomas et al., 2010). These findings suggest beneficial effects on glucose metabolism and improved markers associated with obesity and metabolic syndrome within rodents.
Glucose Metabolism: Human Trials
Human trials, as expected, are very limited when studying the metabolic parameters of glucose. In the meantime, there have been a few observed benefits so far. One study structured a trial using ten subjects with a BMI > 30 and were maintained for 8 weeks on an every other day ad libitum diet, while consuming less than 20% of their normal calorie intake on the following days. James et al., claimed that, “Nine of the subjects adhered to the diet and lost an average of 8% of their initial weight during the study. Their asthma-related symptoms, control, and QOL improved significantly, and PEF increased significantly, within 2 weeks of diet initiation; these changes persisted for the duration of the study” (James et al., 2006). Overall, there were implications indicating a shift in energy metabolism that favored fatty acid utilization, thus confirming compliance with the diet as well.
On the contrary, there was a randomized crossover study using an alternate-day fasting diet that lasted only two weeks and was designed using eight subjects. Results showed no observed differences in body weight, blood lipids, glucose metabolism, or hormone levels. Interestingly, there was also a decrease in energy expenditure (Soeters et al., 2009). Although the data yielded negative results to intermittent fasting, the duration of the fast, and studies done in controlled and uncontrolled conditions should be taken into consideration. Therefore, this study does not provide adequate data to draw conclusions and future studies should implement controlled trials with larger number of subjects and longer study durations in humans to bring supporting evidence to these results.
Prophylactic Intermittent Fasting: Neurodegenerative Diseases
Numerous aspects of intermittent fasting and neuronal effects have been examined across studies using rodent subjects. Therefore, the results that come from such studies cannot draw any conclusions in regard to neuroprotective effects in humans. On that note, the results may provide data that can be replicated in future human trials with the intention of producing similar results.
Vascular Cognition Dysfunction and Neuroprotection of Vascular Dementia
Presently, it is unknown whether or not intermittent fasting can prevent further damage of vascular cognitive dysfunction. Therefore, a study using rat models underwent trials that measured memory, behavior, antioxidative enzymes, and inflammatory protein concentrations over a period of 12 weeks. There were two groups (alternate day fasting and ad libitum) — both of which carried permanent vascular cognition dysfunction. At the end of the trial, the rats that possessed vascular dementia under ad libitum feeding performed poorly during tests given when compared to the rats with vascular dementia under IF pretreatment (Hu, Yang, Zhang, Deng, Zhang, 2017). The data indicates a IF may be a preventative measure for patients that possess vascular cognitive deficits.
Alzheimer’s disease is influenced highly by the polarity distribution of aquaporin-4 (AQP4). In order to reduce or slow the process of impairment caused by this disease, AQP4 must regain its ability to regulate the clearance of myloid-β (Aβ). A study investigated whether intermittent fasting can mitigate or reverse the effects caused by the imbalance of the polarity distribution to see if there is any evidence of protection against Alzheimer’s disease. The study used rat models, and the results showed that, “IF ameliorated cognitive dysfunction, prevented brain from Aβ deposition, and restored the AQP4 polarity in a mouse model of AD” (Zhang et al., 2017). Conclusions can be drawn from the data showing that IF can ameliorate cognitive dysfunction and can be beneficial towards the prevention or reversal of Alzheimer’s disease.
Recent studies have shown that intermittent fasting may mitigate tissue damage and neurological deficit following an ischemic stroke in animal stroke models (Fann, Ng, Poh, Arumugam, 2017). One study questioned whether extending the fasting period alters neurogenesis after ischemic strokes. Data measured cell proliferation, cell death, and neurogenesis in both ad libitum and 3-month IF groups. Results of this study showed that, “IF was associated with twofold reductions in circulating levels of the adipocyte cytokine leptin in intact mice, but also prevented further reductions in leptin after MCAO. IF/MCAO mice also exhibit infarct volumes that were less than half those of AL/MCAO mice” (Manzanero et al., 2014). These findings show that leptim may be a responsible mediator in protecting against neurological damage in ischemic strokes, indicating that IF may be a preventative for these individuals.
One suggestive hypothesis from IF may be to increase the life span of humans, which has been seen across calorie restriction diets in many other organisms. With acknowledgement of there being limited studies that observe intermittent fasting long-term, caloric restriction is usually an indirect result of IF. A study done by The Wisconsin National Primate Research Center concluded that, “Caloric restriction (CR), without malnutrition, delays aging and extends life span in diverse species” (Colman, 2009). These conclusions were made based off of primates, and only focused on caloric restriction. Two other studies propose that animals on alternate-day fasting diets increase life span compared to those fed ad libitum (Goodrick, 1983; Goodrick, 1990). Goodrick’s (1990) study seems to indicate that the increase of life span seems to be dependent on animal strain and age of initiation. In regard to that, one study observed only rats on alternate-day fasting diets survived to 30 months of age compared to a mean lifespan of 22–24 months for rats fed ad libitum (Moroi-Fetters, Mervis, London, Ingram, 1989). Although dietary restriction was the main focus in these studies, this does not conclude that the fasting portion is responsible for the longevity of these animals. With that in mind, it should still be of interest to shift focus on the fasting portion to find any correlations.
No study to date has specifically studied the effect of intermittent fasting without calorie restriction on lifespan, but the effects that have been observed in these studies are great indicators to increasing life span. Interestingly, the largest increase of life span expansion (25 percent increase in mean life span) is seen in C57BL/6J mice, the same strain that in many of the studies on alternate-day fasting maintain a constant total energy intake and body weight (Goodrick, 1990). In response to these findings, the results could not conclude that the loss in body weight was a clear indicator of the increase in longevity. Instead, the study concluded that the results may be greatly dependent upon the genotype and age of dietary initiation. Moreover, this means that reducing overall calories may not be the only causation of longevity.
Safety: Is This Product Safe?
Intermittent fasting has been proven safe for already-healthy adults. Overfeeding, which can lead to obesity-related issues is a serious issue that affects the number of mortality rates; pharmacological approaches do not seem to solve this issue. Instead, studies are pointing to a natural alternative to these approaches that takes advantage of the positive benefits that caloric restriction diets offer. An increasing number of studies are revealing positive results from intermittent fasting methods and have so far not showcased any significant negative outcomes (Carmoci, 2016). Therefore, those who are not negatively affected by caloric restriction diets should experience the same when implementing intermittent fasting and should only expect positive results from it.
There have been reported cases in which intermittent fasting-type feeding causes distress and unwanted conflicts. Those who are either pregnant and breastfeeding, under the age of 18, or anyone who is malnourished and underweight should not be fasting. In addition to that, those with gout, taking medications for diabetes mellitus (both type 1 and type 2), those with Gerd, and also individuals who tend to have eating disorders should take precaution when intermittent fasting. Anyone listed should always consult with a doctor and obtain close supervision when doing IF. On the other hand, individuals who desire to lose weight, or have signs of insulin resistance should invest their energy in intermittent fasting (Fung, 2016).
Ethical and Legal Issues
Human trials are of low incentive for obvious reasons. Fasting is counterintuitive to what most Americans were brought up to believe and goes against conventional wisdom. This creates a non-ethical perspective in most people. In addition to that, the benefits are not conclusive as of now, and require further studies that provide beneficial evidence, which may increase incentive and ethical standards. Therefore, it is likely that this eating pattern will eventually become a more common protocol for weight loss and prevention of diseases when further studies establish a clearer understanding of intermittent fasting’s effects.
As mentioned in the beginning, intermittent fasting has various approaches to it — there is not one-size-fits all approach. With that said, most studies have already investigated many of the effects using alternate-day fasting protocols, which provides purposeful incentive for the public. Alternate day fasts can either include a two-day consecutive fast followed by five days of ad libitum feeding, or it can be modified so that fasting occurs every other day along with ad libitum feeding on subsequent days. Another popular method includes a 24-hour fast at least once a week followed by regular dieting on subsequent days. The most common protocol includes a daily 16-hour fast followed by ad libitum for the other eight hours. This would be considered a time-restricted eating pattern, which creates lifestyle that is more standardized and routine.
Overall, intermittent fasting is a long lost forgotten way of eating, so nothing is new other than what has been forgotten. Looking back to our past, recent changes in our eating behavior does not go that far back in our past. This implies that humans can more than likely still implement this in their lifestyle without causing detriment in their health — we were built to survive long periods of without eating. Nonetheless, evolution takes its course, and human genetic-makeup can vary across each individual, causing more difficulty in accomplishing this lifestyle than in others. With consideration, intermittent fasting may provide promising results for the majority of human health as has been seen across similar organisms throughout recent publications.
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