I Analyzed Bryan Johnson's Biomarkers and The Results Are...

Siim had a homocysteine of 9 µmol/L, which is within normal but not optimal range (optimal <5–7). He specifically used 2 g/day TMG and hyperbaric oxygen therapy, noting that Brian Johnson also does hyperbaric oxygen regularly. He doesn't provide exact session duration or pressure, but the combination dropped his homocysteine significantly. High homocysteine damages endothelium and is linked to heart disease, so he aimed for the low end.

Siim attributes his excellent lipid profile (ApoB 58, LDL 58, triglycerides 39) primarily to his high fiber intake and low saturated fat consumption (olive oil, fish, walnuts, moderate animal protein). He contrasts this with Brian Johnson, who takes a lipid-lowering drug despite also eating plant-based. Siim's fiber intake also helps keep his blood sugar stable even with 300g daily carbs. He emphasizes that he is not taking any medication for lipids.

Siim has been taking saunas since age 2, accumulating ~30 years of regular use. He attributes his exceptionally low resting heart rate (35–39 bpm) and high HRV (>100) partly to this practice, along with genetics and overall fitness. He notes that Johnson only recently started saunas, and predicts his HRV and heart metrics will improve if he continues. Siim emphasizes the combination of hot and cold back-and-forth as particularly effective for HRV.

Siim's entire metabolic profile—fasting glucose 80, HbA1c 4.9%, triglycerides 39, CGM average 81—was achieved while eating 200–300g carbs daily, contradicting the idea that low-carb is necessary for metabolic health. He argues that regular carbohydrate consumption 'trains' insulin sensitivity, while very low-carb diets induce a pseudo insulin resistance state. He also points out that carb restriction raises SHBG, reducing free testosterone, as seen in Johnson. He considers his approach optimal for both metabolic and hormonal health. He emphasizes that he does not need drugs like metformin, which Johnson takes.

Siim's fitness markers show elite or near-elite levels: VO2max 66 (top-tier for any age), grip strength 150 lbs per arm, bench 300 lbs (135 kg), squat 160 kg below parallel. He notes that Johnson's strength and VO2max are 'good for his age' but not elite. He attributes his fitness partly to doing less exercise than Johnson but focusing on quality and recovery, allowing better adaptation. He also mentions that low iron/hemoglobin (Johnson is low) limits VO2max, so diet plays a role.

Siim walked through every category: fitness (VO2max, grip, bench, leg press), body composition (visceral fat, liver fat, bone density), inflammation and immune (homocysteine, CRP, glutathione, uric acid, WBC), metabolic (HbA1c, triglycerides, insulin, glucose, fasting glucose), cardiovascular (ApoB, LDL, HDL, Lp(a), oxidized LDL, BNP, resting heart rate, HRV, blood pressure), omega-3 index, red blood cell markers, kidney (creatinine, cystatin C, EGFR, albumin, total protein, B12, folate), liver enzymes, hormones (testosterone, free T, SHBG, DHEA, IGF-1, thyroid), and experimental aging tests (DunedinPACE, telomeres, PhenoAge). He explained the physiological reasons for differences, such as low iron/hemoglobin from a plant-based diet limiting Johnson's VO2max, high SHBG from calorie/carb restriction lowering free testosterone, and elevated creatinine/cystatin C despite low muscle mass suggesting impaired kidney clearance. He also noted that Johnson's better markers (e.g., omega-3 index, bone density relative to age) were marginal, while the advantages in his own markers were significant and achieved without medications like metformin, lipid-lowering drugs, or thyroid medication, which Johnson uses.

Siim explains that insulin sensitivity is like a muscle; without regular stimulation, the body loses its ability to efficiently handle carbohydrates. When someone follows a very low-carb diet for a long period, the cellular machinery that responds to insulin (GLUT4 translocation, insulin receptor signalling) downregulates. This creates a state where any carbohydrate intake causes exaggerated blood sugar spikes and higher fasting glucose. He contrasts his own diet: he eats 200–300g of carbs daily, yet his CGM average is 81 mg/dL and fasting glucose is 80 mg/dL, while Johnson's are 91 mg/dL and 97 mg/dL respectively. He also notes that some carnivore diet influencers have pre-diabetic blood work despite zero carbohydrate intake, further illustrating the phenomenon. However, he clarifies this is not pathological insulin resistance but a dietary self-induced state that reverses upon reintroducing carbs. His approach maintains high insulin sensitivity because his high muscle mass, fitness, and regular carb intake keep the glucose uptake pathways active. He also emphasizes that this mechanism explains his lower triglycerides (39 vs Johnson's 55) despite eating far more carbohydrates.

Siim explains that the DunedinPACE test does not actually measure biological age or speed of aging; it captures acute inflammation, which can vary depending on time of day, recent exercise, sleep, stress, etc. He tested himself four times and got widely different results. He cites Matt Cberlain, a PhD in geroscience, who tested with multiple companies at the same time and got different results, proving the test is unreliable. Johnson tests 25 times per year, so statistically he is bound to get some low scores by chance. Siim's own best result was 0.62, but he dismisses it as meaningless. He suggests that anyone who tests that frequently will eventually see a number they want. The test does not provide actionable insights because you cannot tell if a high score is due to aging or a transient stressor. He prefers markers like PhenoAge which include concrete blood measurements that can be addressed.

SHBG is produced by the liver and binds testosterone, making it unavailable to tissues. The primary drivers of high SHBG are calorie restriction, carbohydrate restriction, iron overload, and liver damage. In Johnson's case, iron is low and liver markers are mostly fine, so the cause is his very low calorie intake (to maintain extreme leanness) and low carbohydrate consumption. Siim explains that insulin is a pro-anabolic hormone that signals nutrient abundance; it suppresses SHBG production. On a low-carb diet, insulin levels are chronically low, leading to higher SHBG and lower free testosterone. He cites evidence that high-protein, low-carb diets increase SHBG and lower testosterone in men, while even low-protein, high-carb diets lower SHBG. Siim maintains higher free testosterone by eating both adequate protein and high carbohydrates (200–300g), which keeps SHBG at 47 and free T at 13.8. He suggests this is one reason Johnson's muscle mass and strength are not exceptional for his age despite obsessive exercise.

PhenoAge uses 10 blood markers (creatinine, glucose, CRP, lymphocyte %, WBC, RDW, alkaline phosphatase, MCV, age) plus chronological age to estimate biological age. Because the formula includes chronological age, a 47-year-old can show a larger absolute gap than a 30-year-old even with the same blood values. Siim demonstrated that if his blood markers were plugged into Johnson's age, the pheno age would be 20 years lower (i.e., 27), while his own gap is 18.5 years. This shows that Johnson's 8.81-year gap is modest for his age. Siim also references the Longevity World Cup website, a crowdsourced leaderboard using PhenoAge, where Johnson would not place in the top 60. For example, Michael Lustgarten (age 55) has a gap of 23.9 years. Siim acknowledges PhenoAge fluctuates with acute changes (e.g., infection affecting WBC), but it's more actionable because you can see which markers to improve. He concludes that Johnson's biological age claims are unexceptional and that many people outperform him on this metric.