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Fasting

Fasting featured article

Fasting – the voluntary abstinence from food and drink – is an ancient tradition long believed to be vital to humans' physical and spiritual health. Practiced for millennia by various cultures and religious groups, fasting is now widely appreciated for its beneficial effects on human metabolism and healthspan.

A growing body of evidence suggests that in the absence of ready supplies of glucose and fats from meals, fasting flips a metabolic "switch," liberating fat stores via fatty acid oxidation and ketone production while prioritizing the safeguarding of lean muscle mass and function. As such, fasting provides a mechanism that not only improves overall body composition but also triggers the activation of biochemical processes and signaling pathways that optimize human performance and physiological function, possibly slowing the processes of aging and disease.

Fasting also stimulates hormesis, a compensatory defense response following exposure to a mild stressor...

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Episodes

fasting

Does Time-Restricted Eating Have Benefits Independent of Calorie Restriction?

Posted on January 16th 2025 (4 months)

In this clip, Drs. Rhonda Patrick and Layne Norton discuss the benefits, limits, and longevity impacts of time-restricted eating and calorie restriction.

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Q&A #56 with Dr. Rhonda Patrick (2/10/24)

Posted on February 16th 2024 (over 1 year)

Dr. Rhonda Patrick explores creatine, dairy's effect on polyphenols, eggs' health impact, and new weight loss drugs like Ozempic in her latest Q&A.

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Q&A #50 with Dr. Rhonda Patrick (8/5/23)

Posted on August 13th 2023 (almost 2 years)

Dr. Rhonda Patrick explores taurine's longevity role, cocoa flavanols, training adaptations, and oral hyaluronic acid in a Q&A.

Topic Pages

  • Beta-hydroxybutyrate

    Beta-hydroxybutyrate is a ketone body and source of cellular energy produced via the breakdown of fats during carbohydrate scarcity and fasting.

  • Brain-derived neurotrophic factor (BDNF)

    BDNF is a growth factor known for its influence on neuronal health and for its role in mediating the beneficial cognitive effects associated with exercise.

  • Butyrate

    Butyrate is a short-chain fatty acid produced by microbes in the gut during the fermentation of dietary fiber.

  • Fasting

    Fasting – the voluntary abstinence from food and drink – is an ancient practice now widely appreciated for its beneficial effects on healthspan.

  • FOXO

    FOXO proteins are transcriptional regulators that play an important role in healthy aging. Some FOXO genes may increase lifespan.

  • Myocardial infarction (Heart attack)

    A heart attack is a critical and often life-altering event that strikes suddenly, but its underlying causes develop over time.

  • Sirtuins

    Sirtuins play a key role in healthspan and longevity by regulating a variety of metabolic processes implicated in aging.

  • Time-restricted eating

    Time-restricted eating is a form of daily fasting wherein a person eats only during a limited time window, typically 8- to 12-hours.

News & Publications

  • Intermittent fasting three nonconsecutive days per week coupled with regular exercise promotes more weight loss than daily calorie restriction. www.acpjournals.org
    Diet Obesity Fasting Weight Loss

    Diets that require daily calorie cutting are hard to adhere to, and most people gain the weight back within a year. Intermittent fasting, which involves eating very little on some days and freely on others, might offer a more sustainable alternative. A recent study found that fasting three nonconsecutive days per week promoted more weight loss than daily calorie restriction as part of a comprehensive weight loss program.

    Researchers assigned 165 adults aged 18 to 60 with a body mass index between 27 and 46 to one of two diet plans. One group followed a 4:3 intermittent fasting schedule, eating freely on four days of the week and cutting calories by 80% on three nonconsecutive days each week. The second group followed a daily calorie restriction (about 34% less than baseline needs) to match the same total weekly calorie reduction. Both groups also participated in a year-long behavioral weight loss program that included group support and a goal of 300 minutes of moderate exercise weekly.

    After 12 months, participants in the intermittent fasting group lost roughly 6.4 pounds more, on average, than those in the daily calorie restriction group. Just over three-fourths of participants completed the study. The difference in weight loss between the two groups was small but statistically meaningful.

    These findings suggest that intermittent fasting offers a modest advantage over daily calorie restriction for people trying to lose weight, especially when paired with regular exercise and behavioral support. Learn more about the health benefits of intermittent fasting in this clip featuring Dr. Mark Mattson.

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  • Time-restricted eating improves athletic performance. www.mdpi.com
    Exercise Fasting Fat Muscle Time-Restricted Eating

    Time-restricted eating involves restricting the timing of food intake to certain hours of the day (typically within an 8- to 12-hour time window) without an overt attempt to reduce caloric intake. Increasing the amount of time spent fasting each day has been used to treat metabolic diseases such as type 2 diabetes and high cholesterol, increase muscle mass, decrease fat mass, and improve exercise performance. Findings of a recent report demonstrate the beneficial effects of time-restricted eating on exercise performance in power athletes.

    Increasing muscle mass and decreasing fat mass is an important goal for many athletes because increasing their strength-to-mass ratio improves performance. While time-restricted eating is one strategy to improve body composition, previous research has shown that other types of intermittent fasting (e.g., religious fasting during Ramadan) decrease power output and endurance. Another study involving intermittent fasting with caloric restriction found similar deficits in athletic performance. The effects of long-term time-restricted eating without caloric restriction are unknown.

    The researchers recruited healthy young males who were currently practicing a power-sport at least three times per week and had been practicing for at least three years. Twelve participants (average age, 22 years) completed four weeks of time-restricted eating and four weeks of a standard meal pattern in random order with two weeks of wash-out in between. During the time-restricted eating period, participants consumed all of their food within an eight-hour window. The researchers measured body composition using X-ray and athletic performance using the Wingate test, a cycling challenge that measures power and total work.

    Time-restricted eating produced a significant increase in total work (a measure of force over a set distance) and average power output (a measure of work over time). These improvements translated to a one second reduction in sprinting time. The participants achieved this change after four weeks of time-restricted eating, but not after one week. Time-restricted eating did not improve peak power, endurance, or body composition.

    Time-restricted eating, along with regular training, improved exercise performance in athletes. Given that the difference between the current and former 400 meter running world records is only 15 hundredths of one second, the one second decrease in sprinting time produced by time-restricted eating is meaningful.

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  • Intermittent fasting improves long term memory retention in mice. www.sciencedaily.com
    Fasting Memory Ketogenic Diet

    Intermittent fasting is a broad term that describes periods of fasting between meals, lasting several hours to days. Intermittent fasting increases ketone production because it uses stored fat as an energy source. It also activates genetic pathways associated with enhanced healthspan and longevity. Caloric restriction, which typically involves a 10 to 40 percent reduction in total caloric intake, activates similar pathways. Findings from a new study suggest that intermittent fasting is more effective than caloric restriction in activating klotho, a longevity gene, to improve long-term memory retention in mice.

    The klotho gene provides the instructions for making the klotho protein in mammals, including mice and humans. Klotho is produced primarily in the kidneys, but some is produced in the brain, where it appears to play a role in cognition and in neurogenesis, the process of forming new neurons. Neurogenesis is the basis for memory, but it declines with age, leading to cognitive decline.

    The authors of the study assigned mice to one of three feeding regimens: intermittent feeding every other day (approximately 10 percent fewer calories over a one-week period); 10 percent calorie restriction; or eating freely. After the mice had followed their respective feeding regimens for three months, the authors of the study subjected them to behavioral studies (to assess spatial learning and memory, conducted at 24 hours and ten days post regimen) or gene expression studies.

    The memory assessment conducted at 10 days post regimen revealed that the mice in the intermittent feeding group performed 25 percent better than those in the caloric restriction group and 30 percent better than those that ate freely. The mice in the intermittent feeding group also exhibited more signs of hippocampal neurogenesis and upregulation of the klotho gene. Further analysis revealed that adult hippocampal neurogenesis is dependent upon klotho activity.

    These findings demonstrate that the longevity gene klotho is necessary for neurogenesis and that intermittent feeding may be beneficial in promoting memory retention in humans. A ketogenic diet also improves memory in mice. Learn more in this episode featuring aging expert Dr. Eric Verdin.

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  • Intermittent fasting improves gut microbiota composition and markers of metabolic health. academic.oup.com
    Microbiome Fasting

    Intermittent fasting, a dietary practice in which individuals repeatedly, voluntarily, and heavily restrict food intake for approximately 16 to 24 hours, is a popular dietary intervention for weight loss and increased glucose tolerance. Some of the beneficial effects of intermittent fasting arise from its ability to modulate the gut microbiota, the community of microbes that live in the gastrointestinal tract. Findings of a recent report demonstrate the effect of intermittent fasting on microbiota structure and function in adults observing the Islamic faith-associated month of Ramadan.

    There are many health benefits attributed to intermittent fasting with the American Heart Association claiming that intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk for cardiometabolic diseases; however, the mechanisms that drive these benefits in humans are unclear. Experiments in mouse models have suggested that intermittent fasting produces changes in circadian biology and remodeling of the gut microbiota, but further research in humans is needed.

    The investigators recruited two cohorts of participants. The first cohort consisted of healthy young adult males (average age, 19 years) who expressed intention to fast during the month of Ramadan according to Islamic law, which dictates 30 days of fasting from dawn to sunset (approximately 16 hours in this study). These participants provided stool samples for microbiome analysis and blood for the measurement of metabolic makers before the start of Ramadan, 15 days into the month, and at the end of the month. The second cohort consisted of healthy middle-aged adults (average age, 40 years). Some participants in this cohort practiced Ramandan fasting and some did not. Participants in this cohort also provided stool samples for microbiome analysis and blood samples for the measurement of metabolic markers. The researchers collected this data at the beginning and end of the month of Ramadan and 30 days afterward.

    The researchers found that microbiota diversity increased among participants practicing Ramadan-associated intermittent fasting compared to non-fasting participants. This diversity was specifically associated with increased abundance of the bacterial families Lachnospiraceae and Ruminococcaceae. Lachnospiraceae is capable of producing the short-chain fatty acid butyrate, which is a known promoter of metabolic health. Increased abundance of Lachnospiraceae was associated with beneficial changes in liver enzymes. Microbiota composition returned to normal 30 days following the end of Ramadan.

    The authors concluded that intermittent fasting alters the composition of the gut microbiota. Specifically, fasting increased the abundance of the butyrate-producing Lachnospiraceae family, which may explain some of the beneficial physiological effects of intermittent fasting.

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  • Fasting activates multiple metabolic pathways. www.nature.com
    Metabolism Fasting

    Fasting – the voluntary abstinence from food and drink – triggers the activation of a vast array of biochemical processes and signaling pathways that optimize human performance and physiological function, possibly slowing the processes of aging and disease. A recent study found that fasting induced profound, diverse increases in the metabolites present in blood.

    Metabolites are substances produced in an organism, cell, biological fluid, or tissue during metabolism. The collection of these metabolites in their entirety is referred to as the metabolome. Metabolomics is an emerging field of study involving the identification and quantification of the metabolome at a specific time point to create a metabolic profile that provides information about the body’s physiological state. Previous research has identified 126 distinct metabolites in human blood.

    The authors of the study drew blood samples from four healthy, young (average age, xx years) non-obese volunteers at three intervals (10, 34, and 58 hours) during a period of fasting. They analyzed the participants' metabolomic profiles in whole blood, plasma, and red blood cells and identified changes (increases or decreases) in the metabolites. Their analysis revealed that the participants' blood glucose levels remained within the normal range (70 to 80 mg/dL) and ATP levels were consistent throughout the fasting period. Levels of most of the previously identified metabolites remained unchanged during the fast, but 44 metabolites increased, and two decreased.

    Those that increased included butyrate, branched-chain amino acids, carnitines, organic acids, coenzymes, pyrimidines, purines, antioxidants, and molecules associated with the pentose phosphate pathway. These compounds support multiple metabolic pathways and biological processes, including gluconeogenesis (the production of glucose from ketones, glycerol, and amino acids), protein synthesis, and mitochondrial activity, among others. The compounds that decreased were aspartate (an amino acid) and gluconate (a glucose derivative).

    These findings suggest that fasting induces a metabolically active state in healthy, young adults. However, this was a very small study, so larger studies are needed to confirm the findings.

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  • Fasting reduces the numbers of circulating monocytes in healthy humans and mice without compromising immune function. www.mountsinai.org
    Fasting Time-Restricted Eating

    Fasting and other forms of caloric restriction are associated with reduced risk of many chronic diseases. Monocytes, white blood cells that play key roles in the body’s immune response, can contribute to the pathogenesis of chronic inflammatory diseases. Findings from a new study demonstrate that fasting reduces the number of circulating monocytes without compromising immune function.

    The authors of the study analyzed blood samples from 12 healthy adults taken at the beginning of the study (baseline), three hours after they ate, and 19 hours after commencing a fast. All the samples were taken at the same time of day (3pm). After fasting, the participants' blood levels of monocytes were markedly lower than after eating. Fasting did not lower blood levels of monocytes below the normal range in people whose baseline levels were already low.

    The study was replicated in mice, with a fasting protocol suitable for rodents. The outcome was similar, with monocytes drastically reduced. A longer fast in the mice yielded even more favorable reductions in monocytes in various tissues as well as reductions in several types of leukocytes, including eosinophils, natural killer cells, and T cells.

    These findings illuminate the role of dietary intake in the regulation of the body’s immune and inflammatory responses and suggest that fasting and other forms of caloric restriction may be viable strategies to reduce inflammation in chronic disease states.

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  • Intermittent fasting increased gut bacteria diversity, reduced inflammation, demyelination, and axonal damage in multiple sclerosis (MS) animal model. www.cell.com
    Gut Microbiome Fasting Multiple Sclerosis Autoimmunity

    Intermittent fasting (every other day) increased gut bacteria diversity and reduced inflammation, demyelination, and axonal damage in multiple sclerosis (MS) animal model. A small pilot trial in humans with MS showed many similar changes to the gut microbiome and blood adipokines such as leptin. The effects of fasting on immune cells included a reduction of pro-inflammatory IL-17-producing T cells and increased numbers of T regulatory cells which prevent autoimmunity.

    The small pilot trial in humans showed increased bacteria richness in species that have previously been shown to promote T regulatory cell accumulation in the colon.

    Interestingly, this study did what is called a metagenomic analysis and found that the ketone pathway was enhanced in the gut microbiome by intermittent fasting. This is super interesting because bacteria in the gut normally produce short chain fatty acids and ketones from fermentable fiber but suggests that the gut microbiome regulates its own ketone body metabolism during fasting!

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