Habits and Hustle

Episode 509: Renee Fitton: Fast-Mimicking: A Smarter Way to Support Longevity

December 9, 2025

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  • Longevity is defined not just by living longer, but by maximizing 'healthspan' to minimize the 10 to 20 years of unhealthy life often experienced before death. 
  • Prolonged fasting (three to five days) is considered the best type of fasting for longevity because the key cellular repair process, autophagy, is maximally activated around the three-day mark. 
  • Fasting-mimicking diets, like the ProLon program, offer comparable benefits to water-only fasting, including muscle protection and fat loss, while being more sustainable and easier to adhere to. 
  • The research on cold plunging is conflicting, and due to its difficulty and potential for hormone disruption or muscle atrophy in women, infrared sauna use may be a preferable longevity tool. 
  • Fasting mimicking diets are often recommended for women in midlife over daily intermittent fasting because they are gentler on the body while still providing cellular repair benefits, supported by data showing significant female participation in relevant studies. 
  • Athletes should limit activity to light walking and stretching during a five-day fast-mimicking cycle, avoiding high-intensity workouts to prevent layering too much stress on the body, and exogenous ketones should be avoided as they may limit the body's natural ability to produce its own beneficial ketones. 

Segments

Defining Longevity and Healthspan
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(00:06:06)
  • Key Takeaway: The gap between lifespan (average life expectancy) and healthspan (years lived healthily) is currently 10 to 20 years, which longevity efforts aim to close.
  • Summary: Longevity is fundamentally about living healthy longer, not just extending life. Data from the WHO shows people live until 73-79, but their healthspan ends around 61-63. The goal of longevity science is to eliminate this 10 to 20-year period of unhealthy decline.
Lifestyle Factors Driving Decline
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(00:08:10)
  • Key Takeaway: The decline in healthspan is driven by a combination of neglected lifestyle factors, including poor nutrition, lack of sleep, low community connection, and high stress impacting the microbiome.
  • Summary: While knowledge about healthy habits exists, societal structures and personal choices often make healthy living difficult, contributing to earlier sickness. Environmental factors, such as the prevalence of fast food and food deserts, exacerbate these issues. Furthermore, modern culture fosters laziness and isolation, negatively impacting community health.
Fasting Science and Autophagy
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(00:16:17)
  • Key Takeaway: Fasting promotes longevity by limiting growth factors and activating autophagy, a cellular cleanup process that removes accumulated, non-functioning material.
  • Summary: Fasting limits growth factors and growth hormone, which, when excessive, can lead to chronic and age-related diseases. Autophagy, or ‘self-eating,’ is triggered during fasting to hunt down and eliminate damaged cellular components, allowing for new, healthier material to be created.
Optimal Fasting Duration
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(00:18:07)
  • Key Takeaway: For maximal cellular rejuvenation, prolonged fasting of three to five days is recommended, as autophagy is maximally activated around the three-day mark.
  • Summary: Intermittent fasting is less effective for deep cellular cleanup than prolonged fasting. The ideal protocol involves short, focused cycles (three to five days) perhaps quarterly to achieve deep cleanup, followed by periods focused on growth and rebuilding through regular nutrition.
Fasting Mimicking vs. Water Fasting
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(00:24:28)
  • Key Takeaway: Fasting-mimicking diets achieve similar benefits to water-only fasting but are muscle-protective, partly due to specific nutrient inclusion like glycerol.
  • Summary: While direct side-by-side human trials are lacking, fasting-mimicking results mirror those of water-only fasting, with some evidence suggesting it may be superior in specific conditions like IBD due to added beneficial nutrition. The ProLon kits are specifically formulated to stay below nutrient-sensing pathways while including ingredients like glycerol to protect muscle mass.
Benefits of Fast Mimicking Cycles
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(00:37:36)
  • Key Takeaway: Just three cycles of fasting mimicking can reverse biological age by 2.5 years and significantly improve skin health metrics like hydration and fine lines.
  • Summary: Fasting mimicking shows measurable benefits in biological age reversal and skin health, with one five-day cycle improving skin hydration by 25%. Furthermore, participants often report increased energy and physical activity post-cycle, contrasting with sedentary behavior seen in control groups on everyday diets.
Protein Intake Caution
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(00:51:09)
  • Key Takeaway: Excessive protein intake, particularly animal-based protein, may increase the risk of cancer and age-related diseases, despite the current trend pushing high protein consumption for muscle maintenance.
  • Summary: While muscle density is crucial for longevity, the current trend advocating for extremely high protein intake (e.g., one gram per pound) is cautioned against. Research suggests that overconsumption of protein, especially animal protein, can increase the risk of age-related diseases like cancer, highlighting that too much of a good thing can be detrimental.
Saunas and Cold Plunge
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(00:56:47)
  • Key Takeaway: Infrared saunas are highly recommended for longevity, whereas the benefits of cold plunging are now viewed with more skepticism due to conflicting research and the difficulty of the practice.
  • Summary: Infrared saunas are strongly supported for their benefits. The speaker has shifted perspective on cold plunging, noting that while it increases metabolic rate, the overall benefits might be overstated compared to the discomfort it causes. The focus should remain on practices with clearer, consistent evidence.
Sauna vs. Cold Plunge
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(00:56:33)
  • Key Takeaway: Infrared sauna use is strongly supported, while cold plunging’s benefits are conflicting and potentially overstated.
  • Summary: Infrared saunas are considered incredible with good research backing their benefits. The speaker has decreased appreciation for cold plunging due to conflicting research regarding its recovery and general benefits. Cold plunging increases metabolic rate for calorie burning, but the overall advantages may not be as significant as touted, leading the speaker to prefer the sauna.
Fasting Mimicking for Menopause
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(00:58:56)
  • Key Takeaway: Fasting mimicking is recommended for women, especially in midlife, as it mitigates the stress response and cortisol concerns associated with daily fasting.
  • Summary: Concerns about fasting for women often stem from limited research, but fasting mimicking has substantial data showing benefits across female participants. Daily intermittent fasting, particularly skipping breakfast, can be dysregulating due to the stress response and cortisol levels. Physicians recommend fasting mimicking for women in midlife because it is gentler while still achieving desired longevity benefits.
Exercise During Fasting Cycles
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(01:00:35)
  • Key Takeaway: Intense exercise should be limited to light walking or stretching during the five days of a fast-mimicking protocol.
  • Summary: The official recommendation during the five-day protocol is to limit activity to light walking, stretching, and recovery. Athletes should schedule these cycles during their off-season rather than mid-season when training intensity is high. Layering intense exercise with the stress of fasting creates too much overall stress on the body; alternative activities like meditation or light yoga are suggested.
Exogenous Ketones and Bone Broth
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(01:02:41)
  • Key Takeaway: Hacking ketosis with exogenous ketones or consuming protein like bone broth during a fast negates the body’s natural benefits.
  • Summary: Exogenous ketones may increase blood ketones but lose the benefits derived from the body performing the work to create them from fat stores. Taking supplemental ketones might even limit the body’s ability to produce its own, which is part of the magic of fasting. Consuming protein, such as bone broth, during a fast-mimicking period will ruin the intended benefits, which is why ProLon kits use plant-based soups.
Guest Contact Information
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(01:06:26)
  • Key Takeaway: Renee Fitton can be found on Instagram and her website, with specific links provided for ProLon and L-Nutra Health.
  • Summary: Renee Fitton is available on Instagram at @fittonnutrition and her website, fittonnutrition.com. Those interested in ProLon kits should visit prolonlife.com. For advanced longevity reasons related to disease and metabolic health, the company L-Nutra Health (l-nutra-health.com) is recommended.