#108 - AMA #13: 3-day fasting, exogenous ketones, autophagy, and exercise for longevity
In this AMA, Peter Attia and Bob Kaplan discuss Peter's shift to a 3-day monthly fasting regimen, comparing it to longer fasts. They also cover physiological changes during fasting, ketone measurement, and resources for health and longevity.
Deep Dive Analysis
6 Topic Outline
Comparison of 3-day vs. 7-day fasting regimens
Physiological and experiential differences in shorter fasts
Impact of diet on ease of fasting and ketone production
Accuracy and utility of ketone measuring devices
Potential effects of non-nutritive sweeteners on ketosis
Discussion on continuous glucose, ketone, and insulin monitoring
3 Key Concepts
Glycogen Depletion
Glycogen depletion refers to the reduction of stored glucose in the body. During shorter fasts, the body experiences less glycogen depletion compared to longer fasts, which can lead to higher exercise tolerance.
Nutritional Ketosis
Nutritional ketosis is a metabolic state achieved through dietary changes, typically low-carb, where the body produces ketones for energy. Ketone measuring devices are considered more helpful for guiding individuals into this state than during prolonged fasting.
Placebo Effect
The placebo effect describes how a person's expectation or belief can influence their experience, such as feeling better or worse during a fast. This is distinct from objective physiological measurements like ketone levels, which are not subject to the placebo effect.
5 Questions Answered
The 3-day fasts are easier to complete and less intrusive than 7-day fasts, and exercise tolerance appears higher due to less glycogen depletion.
A 4-day fast showed almost identical lab results to 7-8 day fasts, including unmeasurable insulin, very low glucose, high uric acid, low free T3, high reverse T3, low testosterone, and very low IGF.
Peter observed that consuming diet Cokes and sugarless gum during a fast was correlated with lower ketone levels and feeling more miserable, suggesting non-nutritive sweeteners might impair ketosis.
Ketone testing devices are primarily helpful during nutritional ketosis to guide the process, and during fasting, they can serve as a way to 'gamify' the experience, though their practical relevance during fasting is questioned.
Continuous ketone meters are likely to become available within the next few years, similar to continuous glucose meters, but continuous insulin monitoring is a more complex and challenging topic.
8 Actionable Insights
1. Adopt 3-Day Monthly Fast
Consider switching from a quarterly 7-day fast to a monthly 3-day fast, as Peter Attia found it less intrusive, easier to manage, and allowed for higher exercise tolerance while potentially yielding similar metabolic benefits.
2. Avoid Non-Nutritive Sweeteners
Avoid consuming non-nutritive sweeteners (like those in diet sodas or sugarless gum) during fasting, as they were associated with lower ketone levels and increased misery, potentially impairing ketosis.
3. Adopt Low-Carb Diet
Follow a low-carb diet by avoiding sugar and starch and focusing on vegetables, as this dietary restriction can make it easier to transition into and out of fasting periods.
4. Test Blood After Fasting
Conduct a blood test after a 3-day fast to assess metabolic changes, as a 4-day fast showed similar signature findings (e.g., very low insulin, glucose, IGF-1, free T3, testosterone; very high uric acid, reverse T3) to longer fasts.
5. Maintain Fasted Exercise Intensity
During 3-day fasts, exercise tolerance seems higher, allowing for intense workouts (e.g., two hours of sled work, deadlifts, compound movements) without significantly reducing volume, unlike longer fasts.
6. Use Ketone Tests as Guide
Use ketone testing primarily as a guidepost, finding it more helpful for achieving nutritional ketosis than for strict monitoring during fasting, where its relevance for actionable changes is less clear.
7. Choose Accurate Ketone Meter
When measuring blood ketones, consider using the Precision Xtra device as it appears to be more accurate at lower ketone levels compared to Keto Mojo.
8. Consider Breath Ketone Testing
If cost or aversion to finger pricking is a concern, breath ketone testing offers a cheaper and more accessible alternative to blood ketone testing, though historical correlation with blood BHB has been poor.
3 Key Quotes
For the three-day fasts, I seem to skate through them a little bit easier.
Peter Attia
I've never had lower ketones and I've never felt more miserable during a fast.
Peter Attia
During fasting, it's just kind of a way to gamify it a little bit.
Peter Attia
1 Protocols
Peter's 3-Day Monthly Fasting Regimen
Peter Attia- Fast for three days once a month.
- Maintain a low-carb diet (no sugar, hardly any starch, mostly vegetables) between fasts.
- Avoid non-nutritive sweeteners during the fast.