Bryan Johnson, the tech entrepreneur known for his extreme anti-aging protocol, has launched what he’s calling “the most ambitious experiment yet” in his quest to reverse biological aging.
This time, he’s not the subject.
Kate Tolo, a member of Johnson’s team, is about to become what Johnson describes as “the most measured female in history,” undergoing a months-long protocol tracking hundreds of biomarkers across every phase of her menstrual cycle.
The experiment highlights a glaring gap in health and longevity research: women have been dramatically under-measured and under-studied compared to men.
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The Scope of the Female Measurement Project
Johnson’s new experiment dwarfs even his own notorious self-experimentation regimen. Tolo will spend several months maintaining an identical daily routine while researchers track 1,900 biomarkers across 16 biological systems, generating 14.8 million data points using over 50 different devices.
The annual cost? A staggering $2.6 million.
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My entire apartment got redone. This doesn’t fit in here.
Tolo’s living space has been transformed into what amounts to a personal longevity clinic, packed wall-to-wall with measurement devices and monitoring equipment. Every second of her day is accounted for, with Johnson noting she has “one, two, three, four, five different types of days” and over 100 tasks to complete daily.
Why Women Have Been Left Out of Longevity Research
Johnson acknowledges a fundamental limitation in his five years of self-experimentation: his data comes from a single male subject. Women, he notes, “experience dramatically different biological changes across every month, every life stage, and almost every system of the body.”
The challenges of measuring women rigorously are substantial. Female bodies undergo cyclical hormonal changes throughout each menstrual cycle, making standardization difficult for traditional randomized controlled trials.
It is incredibly difficult to measure women in a rigorous way according to our current scientific standards for randomized controlled trials. So you can start to see just how difficult this gets to put into practice.
This complexity has historically led researchers to focus on male subjects, creating a massive data gap that affects women’s health outcomes across the board.
The Reality of Being the “Most Measured Female”
Tolo’s experience reveals just how demanding—and invasive—comprehensive health tracking can be. Perhaps most striking is the disparity in available technology for measuring male versus female bodies.
One device perfectly illustrates this gap: a monitor for nocturnal arousal cycles. While men can use a small, wireless device, Tolo must sleep with a large, complicated apparatus inserted and taped to her leg with masking tape.
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I don’t have like the luxury of small wireless Bluetooth data offloaded thing. It’s this beast. Like it’s a very complicated device.
Johnson reflected on what this technological disparity represents about the broader state of female health measurement.
The level of readiness for the world to measure men versus women is captured in that. The device for a man small, easy, consistent. For a female a gigantic device, 16 different things to change.
Preparation and Emotional Journey
While it took Johnson five years and a team of doctors to develop his personal protocol, Tolo’s version was created in just 90 days—an accelerated timeline that contributed to the intensity of preparation.
I feel like I’ve been in preparation mode for the last 4 months and I’m finally ready to take it on.
Tolo described oscillating between various emotional states throughout the preparation process: “feeling not ready, ready, panicked, joy, excited.” The reality of becoming a living experiment—observed and measured at every moment—carries significant psychological weight.
Her schedule is meticulously organized, displayed on a clipboard with every single second accounted for. Johnson joked that despite his five years of experience, he has “nothing of the sort” and keeps everything “in his head.”
Why This Experiment Matters Beyond One Woman
Johnson anticipates critics will dismiss findings as limited to a single subject. But he views Tolo’s experiment as an essential “entry point” to a larger mission: developing better methods and intuitions for measuring female biology.
We talk about adventurous things like going to the moon and like doing big things, but like what about understanding the female body? Why isn’t that a gigantic ambition for society?
Through personally observing Tolo’s experience, Johnson gained newfound empathy for women’s health challenges.
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Given the number of things that Kate is doing, I feel very empathetic to a female’s experience. Even just like in very practical things like how well quantified are females relative to men, not as much. How much data is there on females relative to men? Not as much.
The Practical Challenges of Daily Measurement
Implementing the protocol presents countless unexpected obstacles. Small details—like what type of tape to use for securing devices—become significant problems when dealing with 100+ daily tasks.
There’s 100 things like this, you know, and like, nobody’s going to be able to know besides me.
Johnson acknowledges the overwhelming nature of the protocol, admitting he feels “very empathetic” watching someone else undertake such intensive measurement. The experience has been “really really overwhelming” for both participants.
As motivation, Tolo negotiated an unusual reward: if she completes the protocol, she gets “three nights of sleep in the same bed” as Johnson—presumably to measure sleep data in proximity, though Johnson humorously appeared reluctant to agree.
Whether this experiment yields groundbreaking insights into female biology or simply demonstrates the impracticality of such extreme measurement remains to be seen. What’s already clear is that understanding women’s bodies at this level requires entirely different approaches, technologies, and investments than have traditionally been available.
