SCIENCE EPISODE
SCIENCE EPISODE
Fasting has become a buzzword in health and wellness, with many swearing by time-restricted feeding (also called intermittent fasting) for weight loss, better health, and even longer lives. But is it all it’s cracked up to be? Let's break it down.
The idea that fasting extends lifespan began with a 1982 study in rats, which showed an 80% increase in lifespan with alternate-day feeding. (read study) However, later studies on rats, mice, and monkeys produced mixed results. For example, monkeys on a high-sugar diet lived longer when fasting, while monkeys eating healthy whole foods showed little to no lifespan increase with fasting. (read studies here and here)
In humans, there hasn't been a good study on the impact of caloric restriction or fasting on lifespan to date.
This suggests that if you’re eating a diet full of starch and sugar, cutting back on how much you eat and how often can make a big difference. But if you’re already eating healthy, fasting doesn’t seem to do much—and you might not even need it.
While we lack clear evidence that fasting extends human lifespan, exercise consistently shows stronger, proven benefits—adding up to 7–10 years to life. (read study)
Even if lifespan extension isn’t guaranteed, fasting has clear health benefits. A big review study from 2019 reviewed the impact of fasting (read study). Here are some of the benefits:
Fasting isn’t a magic bullet, and there are some concerns to keep in mind:
Fasting can be powerful, especially for improving insulin resistance and metabolic flexibility. However, it’s not a one-size-fits-all solution. Whether or not you fast, what you eat matters more than when you eat. Focus on improving your overall diet, and if you choose to fast, get the most out of it by focusing on these tips:
Bredesen D E, "Reversal of cognitive decline: a novel therapeutic program," Aging (Albany NY) 6, no. 9 (2014): 707-717, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4221920/
Colman R J et al., “Caloric restriction delays disease onset and mortality in rhesus monkeys.” Science (New York, N.Y.) 325, no. 5937 (2009): 201-4. https://pubmed.ncbi.nlm.nih.gov/19590001/
Cook F et al., “Compliance of participants undergoing a '5-2' intermittent fasting diet and impact on body weight.” Clinical nutrition ESPEN 52 (2022): 257-261, https://pubmed.ncbi.nlm.nih.gov/36513463/
Debnath J et al., “Autophagy and autophagy-related pathways in cancer.” Nature reviews. Molecular cell biology 24, no. 8 (2023): 560-575. https://pubmed.ncbi.nlm.nih.gov/36864290/
Goodrick C L et al., “Effects of intermittent feeding upon growth and life span in rats.” Gerontology 28, no. 4 (1982): 233-41. https://pubmed.ncbi.nlm.nih.gov/7117847/
Kapogiannis D et al., “Brain responses to intermittent fasting and the healthy living diet in older adults.” Cell metabolism 36, no. 8 (2024): 1668-1678.e5. https://pubmed.ncbi.nlm.nih.gov/38901423/
Kim J et al., “Early Time-Restricted Eating Reduces Weight and Improves Glycemic Response in Young Adults: A Pre-Post Single-Arm Intervention Study.” Obesity facts 16, no. 1 (2023): 69-81, https://pubmed.ncbi.nlm.nih.gov/36318892/
Leclerc E et al., “The effect of caloric restriction on working memory in healthy non-obese adults.” CNS spectrums 25, no. 1 (2020): 2-8. https://pubmed.ncbi.nlm.nih.gov/30968820/
Liao C-Y et al., “Genetic variation in the murine lifespan response to dietary restriction: from life extension to life shortening.”Aging cell 9, no. 1 (2010): 92-5. https://pubmed.ncbi.nlm.nih.gov/19878144/
Mattison J A et al., “Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study.” Nature 489, no. 7415 (2012): 318-21. https://pubmed.ncbi.nlm.nih.gov/22932268/
Mattson M P et al., “Impact of intermittent fasting on health and disease processes.” Ageing research reviews 39 (2017): 46-58. https://pubmed.ncbi.nlm.nih.gov/27810402/
Patikorn C et al., “Intermittent Fasting and Obesity-Related Health Outcomes: An Umbrella Review of Meta-analyses of Randomized Clinical Trials.” JAMA network open 4, no. 12 (2021): e2139558. https://pubmed.ncbi.nlm.nih.gov/34919135/
Ran L et al., “Associations of Muscle Mass and Strength with All-Cause Mortality among US Older Adults.” Medicine and science in sports and exercise 50, no. 3 (2018): 458-467. https://pubmed.ncbi.nlm.nih.gov/28991040/
Reimers C D et al., “Does physical activity increase life expectancy? A review of the literature.” Journal of aging research 2012 (2012): 243958. https://pubmed.ncbi.nlm.nih.gov/22811911/
Solianik R et al., “Two-day fasting evokes stress, but does not affect mood, brain activity, cognitive, psychomotor, and motor performance in overweight women.” Behavioural brain research 338 (2018): 166-172. https://pubmed.ncbi.nlm.nih.gov/29097329/
Swindell W R. “Dietary restriction in rats and mice: a meta-analysis and review of the evidence for genotype-dependent effects on lifespan.” Ageing research reviews 11, no. 2 (2012): 254-70. https://pubmed.ncbi.nlm.nih.gov/22210149/
Templeman I et al., “A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults.” Science translational medicine 13, no. 598 (2021): eabd8034. https://pubmed.ncbi.nlm.nih.gov/34135111/
Vernieri C et al., “Cyclic fasting-mimicking diet in cancer treatment: Preclinical and clinical evidence.” Cell metabolism 36, no. 8 (2024): 1644-1667. https://pubmed.ncbi.nlm.nih.gov/39059383/
Zhao L et al., “Time-restricted eating alters the 24-hour profile of adipose tissue transcriptome in men with obesity.” Obesity (Silver Spring, Md.) 31, Suppl 1 (2023): 63-74, https://pubmed.ncbi.nlm.nih.gov/35912794/
Your cart is currently empty.