Key Moments
Results from Peter's 3 week "nothingburger" (1 week keto—1 week fast—1 week keto) (AMA #2)
Peter Attia MDKey Moments
Peter Attia discusses his 3-week "nothingburger" (keto-fast-keto) experiment, detailing metabolic and hormonal changes observed.
Key Insights
First week (keto) showed minor keto flu symptoms, increased magnesium needs, and elevated LDL particle numbers, despite minimal subjective changes.
The one-week water-only fast led to significant drops in total cholesterol, LDL, HDL, and a pronounced negative impact on thyroid function (reduced free T3, increased reverse T3).
Fasting also caused a surge in uric acid, potentially due to DNA turnover from muscle breakdown, and a significant decrease in sex hormones (testosterone) and IGF-1.
Weight loss during the fast was less than expected, suggesting metabolic rate adjustment.
The refeed week on a ketogenic diet saw triglycerides spike unusually high and LDL particle numbers drop unexpectedly, with tentative explanations including dairy intake.
Thyroid and sex hormone levels began to recover after the refeed, but LDL particle numbers and triglycerides remained anomalous, requiring further monitoring.
INITIATING THE EXPERIMENT: THE KETOGENIC WEEK
The experiment began with a week of nutritional ketosis. Peter Attia experienced mild 'keto flu' symptoms, primarily orthostatic dizziness, which he managed by doubling his magnesium intake. He noted that while subjective feelings of well-being and workout performance remained largely unchanged, his lab work revealed significant shifts. Notably, triglycerides increased unexpectedly from 54 to 90 mg/dL, and LDL particle number (LDL-P) rose substantially from 920 to 1380, indicating a less favorable lipid profile according to his metrics.
METABOLIC AND HORMONAL CHANGES DURING KETOSIS
Beyond the lipid profile, the initial ketogenic week also affected other biomarkers. Uric acid increased from 4.8 to 6.6 mg/dL, and homocysteine bumped up to 11. Most strikingly, thyroid function showed signs of peripheral hypothyroidism, with free T3 decreasing from 3.7 to 2.5 ng/dL and reverse T3 increasing from 11 to 17, resulting in a diminished free T3/reverse T3 ratio of 0.15. This occurred despite a weight loss of just over four pounds, suggesting a metabolic slowdown.
THE SEVEN-DAY WATER-ONLY FAST
Following the ketogenic week, Peter embarked on a strict seven-day water-only fast, consuming only water and occasionally bullion for sodium. This period saw significant changes in his health markers. Total cholesterol dropped to 90 mg/dL, and LDL cholesterol plummeted to an unprecedented 37 mg/dL. Inflammatory markers like CRP and oxidized LDL improved considerably, indicating reduced inflammation. However, uric acid skyrocketed to 8.0 mg/dL, a level potentially risky for gout.
IMPACT OF FASTING ON ENDOCRINE FUNCTION AND BODY COMPOSITION
Thyroid function was severely impacted during the fast, with free T3 dropping to 1.8 ng/dL and reverse T3 rising to 38, yielding a critical ratio of 0.05, indicative of significant metabolic slowdown. Sex hormones also declined sharply, with total testosterone falling to 539 ng/dL and free testosterone to 7.8 ng/dL, placing him at the 15th percentile. IGF-1 also decreased significantly to 93. Weight loss during the fast was approximately eight pounds, less than anticipated given his previous fasting experiences.
THE REFEED WEEK: UNEXPECTED TRIGLYCERIDE SPIKE
Upon reintroducing food, Peter followed a ketogenic diet, though his first meal was slightly higher in carbohydrates. A surprising observation was an extreme spike in triglycerides, which became cloudy in the serum, and an unexpectedly low LDL-P of 516, with small LDL particles becoming immeasurable. This reversed the typical trend of LDL-P increasing on a ketogenic diet. He also noted a slight increase in CRP to above 1, which he speculates might be linked to high dairy consumption (heavy cream) in this period.
RECOVERY AND LINGERING ANOMALIES
In the week following the refeed, several markers began to normalize. Uric acid and homocysteine returned to baseline levels. Thyroid function showed improvement, with the free T3/reverse T3 ratio increasing to 0.21. Sex hormones also rebounded, with free testosterone rising to 13.3 ng/dL. However, the anomalous high triglycerides and extremely low LDL-P persisted, suggesting potential ongoing metabolic recalibration or the need for further investigation into these specific markers on a ketogenic diet.
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After one week on a ketogenic diet, the speaker noted mild 'keto flu' symptoms like lightheadedness, an increase in LDL particle number and small LDL particles, a rise in triglycerides and uric acid, and a decrease in free T3 with a rise in reverse T3, indicating reduced peripheral thyroid function. Some improvements were also seen in free testosterone and IGF levels.
Topics
Mentioned in this video
A metric the speaker is maniacal about keeping low (below 5) due to its impact on blood pressure and atherosclerosis. It spiked significantly after the fast.
An inactive form of thyroid hormone. It increased during the ketogenic week and significantly during the fast, showing a marked improvement during the refeed.
A key metric the speaker monitors, aiming for levels below 800 animal per liter; baseline was 920, increasing to 1380 after week 1, and dropping significantly after fasting and refeeding.
This hormone level was around the 50th-55th percentile at baseline and saw changes throughout the experiment.
A key indicator of thyroid function. Baseline was 0.34, dropped to 0.15 after ketosis, and severely to 0.05 after fasting, before improving to 0.21 after refeeding.
A metric the speaker monitors, aiming for levels below 9. It increased after the ketogenic week but corrected after the fast.
A fat cell-derived hormone that typically rises with lipolysis, but showed no change for the speaker during the fast despite high free fatty acids and unmeasurable insulin.
This hormone, typically around 3, decreased during the fast and then rose back to baseline during the refeed week.
The final phase of the experiment, where the speaker returned to a ketogenic diet, with initial meals potentially slightly higher in carbs and vegetables.
The speaker suggests thyroid function hit during ketosis might indicate a shutdown of metabolic rate to conserve energy.
Speculated as a potential reason, alongside DNA turnover, for the uric acid spike after fasting, though not explicitly confirmed.
Mentioned as a reference point for extremely low LDL-C levels, implying the speaker's post-fast LDL-C was very low but not at that extreme.
A marker the speaker monitors, preferring levels below 1 and ideally below 0.5.
This lipid marker unusually increased during the ketogenic week and remained surprisingly high after the fast, before showing a significant elevation after refeeding.
Desired to be below 500, it increased to almost 800 after week 1, returned to baseline after fasting, and became unmeasurable after refeeding.
Levels were very high during the fast, consistent with increased lipolysis.
This blood component decreased during the fast, suggesting a reduction in production rather than dilution, and started to recover during the refeed.
The state achieved during the first week of the experiment, with subjective experiences and lab changes noted.
The speaker experienced mild symptoms, described as lightheadedness and orthostatic intolerance, during the first week of ketosis.
Discussed as a potential link to sex hormone production, though the speaker ultimately discounts a simple substrate-driven explanation.
A metric the speaker aims to keep below 40.
Active thyroid hormone. It decreased significantly during the ketogenic week and further during the fast, improving during the refeed but not fully recovering.
This blood component decreased during the fast, suggesting a reduction in production rather than dilution, and started to recover during the refeed.
The experiment involved periods on a ketogenic diet, which the speaker found led to increased LDL P, reduced IGF (over longer periods), and a hit to peripheral thyroid function.
The second phase of the experiment, lasting approximately seven days, which led to significant changes in lipids, uric acid, thyroid function, and hormones.
This measure decreased after the fast, which is expected given the lack of protein intake.
This hormone, typically around 7, decreased during the fast and then rose back to baseline during the refeed week.
A device used for spot checking glucose levels during the fasting period.
A device used for spot checking glucose levels during the fasting period.
Used as needed during the fast and quite regularly during ketosis week for sodium supplementation.
Consumed as part of the lunch during the ketogenic diet week.
Consumed in large quantities during the refeed week, potentially contributing to the rise in CRP.
A continuous glucose monitor known for its accuracy, not requiring calibration.
The speaker discusses doubling their magnesium intake during ketosis to counteract potential cramping and lightheadedness caused by sodium and potassium excretion.
A component added to coffee during the ketogenic diet phase.
Mentioned as being wasted by the body during ketosis, leading to potential cramping and lightheadedness if not supplemented.
Consumed as part of the lunch during the ketogenic diet week.
Mentioned as being shunted out of the kidney along with magnesium when the body tries to conserve sodium during ketosis.
Consumed as part of the lunch during the ketogenic diet week.
Total cholesterol and LDL cholesterol remained virtually unchanged after week 1 but plummeted to very low levels after the fast.
This marker, an acute phase reactant and indicator of inflammation, doubled during the fast but remained within the normal range.
Mentioned as a more potent hormone than testosterone for stimulating red blood cell production.
Co-authored a paper with Dom D'Agostino, Matthew Vander Heiden, and Luke Ian Lee, which discussed energy uptake into cells, relevant to the discussion on cholesterol.
Co-authored a paper with Craig Thompson, Matthew Vander Heiden, and Luke Ian Lee, which discussed energy uptake into cells, relevant to the discussion on cholesterol.
The world's expert on uric acid, whom the speaker intends to consult for a more in-depth assessment of his own uric acid spike.
Co-authored a paper with Dom D'Agostino, Craig Thompson, and Luke Ian Lee, which discussed energy uptake into cells, relevant to the discussion on cholesterol.
Co-authored a paper with Dom D'Agostino, Craig Thompson, and Matthew Vander Heiden, which discussed energy uptake into cells, relevant to the discussion on cholesterol.
One of two ways to get an NMR done in the US, using an older generation magnet for Lipo Science NMR.
Developed the NMR technology used by both Labcorp and THD, with different magnet generations influencing results.
One of two ways to get an NMR done in the US, using a newer generation magnet for Lipo Science NMR, believed to be more accurate.
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