Features Science Compare Pricing About Download
THE SCIENCE

Tracking works.
Here's the evidence.

Everything Birll measures is there because peer-reviewed research says measuring it changes outcomes. The key findings, by domain — with sources.

01 — FOOD TRACKING

Writing it down
doubles results.

Dietary self-monitoring is one of the most replicated findings in behavioral health: the act of recording what you eat changes what you eat.

In Birll

Log meals by photo or text; macros and timing land next to your glucose, weight and recovery.

In a ~1,700-person NIH-funded trial, participants who kept daily food records lost twice as much weight as those who kept none — diary frequency was the strongest predictor of weight loss.
Hollis et al. · American Journal of Preventive Medicine · 2008 · Kaiser Permanente Center for Health Research
#1
A systematic review of self-monitoring studies found dietary self-monitoring consistently associated with weight-loss success — the leading behavioral predictor across trials.
Burke et al. · Journal of the American Dietetic Association · 2011 · systematic review
02 — BLOOD PRESSURE

Self-monitoring
moves the number.

Home readings beat the once-a-year clinic snapshot — and the act of monitoring, paired with support, lowers pressure itself.

In Birll

Cuff readings trend beside your cardiovascular markers, sleep and stress load.

−3.2 mmHg
Across 25 randomized trials (~7,100 patients), self-monitoring lowered clinic systolic pressure by 3.2 mmHg at 12 months versus usual care — and up to 6.1 mmHg when paired with structured support.
Tucker et al. · PLOS Medicine · 2017 · individual-patient-data meta-analysis
+9%
Self-monitoring also increased the likelihood of reaching blood-pressure targets (relative risk 1.09) across 12 randomized trials.
Bray et al. · Annals of Medicine · 2010 · meta-analysis of 25 RCTs
03 — BLOOD GLUCOSE

Your response is
yours alone.

Two people can eat the identical meal and produce opposite glucose curves. Generic dietary rules can't see that — continuous data can.

In Birll

CGM or finger-stick readings charted against your meals, sleep and training — so you learn what spikes you.

n=800
In an 800-person continuous-glucose-monitoring cohort, post-meal glucose responses to identical foods varied enormously between people — and personal features predicted responses better than universal rules.
Zeevi et al. · Cell · 2015 · Weizmann Institute personalized-nutrition study
−0.6% HbA1c
In randomized trials, continuous glucose monitoring improved long-term glucose control versus fingerstick care alone in insulin-treated diabetes.
Beck et al. (DIAMOND trial) · JAMA · 2017 · randomized controlled trial
04 — HRV

The nervous system,
measurable.

Heart-rate variability indexes how your autonomic nervous system is coping — and it responds to training, both physical and respiratory.

In Birll

Nightly HRV behind your recovery score, plus guided breathwork with live biofeedback.

24 studies
A meta-analysis of 24 studies found HRV biofeedback training produced large reductions in self-reported stress and anxiety.
Goessl et al. · Psychological Medicine · 2017 · meta-analysis
Risk marker
Lower HRV is associated with a higher risk of first cardiovascular events in population studies — making the nightly trend worth watching.
Hillebrand et al. · Europace · 2013 · dose-response meta-analysis
Guided
Training plans guided by daily HRV produced equal or better fitness gains than fixed predefined plans in controlled studies of endurance training.
Kiviniemi et al. · European Journal of Applied Physiology · 2007 · controlled trial
05 — WEIGHT

The scale, used
gently, works.

Regular self-weighing is consistently tied to better weight outcomes — it's the trend that matters, not any single morning.

In Birll

Smart-scale trends smoothed over weeks, read against training and nutrition — never a single-day verdict.

↑ loss
A systematic review found regular self-weighing was associated with greater weight loss and less regain across interventions, with no consistent adverse psychological effects in adults.
Zheng et al. · Obesity · 2015 · systematic review
75%
Among people who have maintained large weight losses long-term in the National Weight Control Registry, roughly three-quarters weigh themselves at least weekly.
Butryn et al. · Obesity · 2007 · National Weight Control Registry
06 — MENSTRUAL CYCLE

A vital sign,
officially.

The cycle is a monthly readout of underlying health — and its phases measurably interact with training, sleep and recovery.

In Birll

Phase-aware tracking: recovery and readiness adjust to where you are in your cycle.

Vital sign
The American College of Obstetricians and Gynecologists recommends clinicians treat the menstrual cycle as a vital sign — irregularity can flag underlying conditions early.
ACOG Committee Opinion No. 651 · 2015
Phase effects
A meta-analysis of 78 studies found exercise performance varies across cycle phases — with effects that differ enough between individuals that personalized tracking is recommended over generic rules.
McNulty et al. · Sports Medicine · 2020 · systematic review & meta-analysis
07 — ACTIVITY

Steps are
dose-response.

Daily movement is the single most powerful lever in the dataset — and the benefit curve is steepest exactly where most people are.

In Birll

Steps, workouts and strain from any device, read against your own baseline — not a generic 10,000.

40–53%
Across 15 cohorts (~47,000 adults), the more-active step groups had a 40–53% lower risk of death than the least-active group (~3,500 steps/day).
Paluch et al., Steps for Health Collaborative · The Lancet Public Health · 2022 · meta-analysis
6–10k
Benefits rose incrementally and levelled off around 6,000–8,000 steps/day for adults 60+, and 8,000–10,000 for younger adults — well short of the mythical 10,000-step rule for older adults.
Same study · The Lancet Public Health · 2022
08 — CORRELATIONS

You are not
the average.

Population studies tell you what works on average. Your own data tells you what works for you — if it's read carefully, with honest uncertainty.

In Birll

Birll surfaces your correlations — bed before 11pm → +9 recovery — labels its confidence, and never dresses correlation up as causation.

n-of-1
Researchers have argued in Nature that medicine should run "one-person trials": systematically testing what works on the individual, because responders and non-responders vanish inside population averages.
Schork · Nature · 2015 · "Time for one-person trials"
Personal
The 800-person glucose cohort made the same point empirically: individual factors out-predicted universal dietary rules — the strongest signals only appear when your own data is correlated against itself.
Zeevi et al. · Cell · 2015
09 — VITALS

Overnight numbers
see trouble first.

Resting heart rate, respiratory rate and temperature drift before you feel anything — the quiet early-warning layer of the body.

In Birll

RHR, respiratory rate, SpO₂ and skin temperature captured nightly; deviations from your baseline get flagged in the morning.

63%
In a Stanford study, smartwatch data — chiefly resting-heart-rate shifts — flagged roughly two-thirds of COVID-19 cases before or at symptom onset.
Mishra et al. · Nature Biomedical Engineering · 2020
RHR ↑
In the Copenhagen Male Study, a rising resting heart rate over time was associated with significantly higher long-term mortality — trend, not snapshot, is the signal.
Jensen et al. · Heart · 2013 · 16-year cohort
10 — HEALTH RECORDS

Owning the record
changes care.

When people can actually see their own clinical information, they understand more, remember more, and follow through more.

In Birll

Labs, vitals and history in one exportable record you control — bring it to any appointment, or delete it in a tap.

99%
In the OpenNotes study (~13,000 patients across three health systems), patients reading their clinicians' notes reported feeling more in control of their care, many reported better medication adherence — and at the end, virtually all wanted continued access.
Delbanco et al. · Annals of Internal Medicine · 2012
Engaged
Follow-up studies of shared records continue to find patients who read their records report better understanding of their conditions and care plans.
Walker et al. · Journal of Medical Internet Research · 2019 · OpenNotes follow-up

SOURCES DESCRIBE FINDINGS IN THEIR STUDY POPULATIONS; INDIVIDUAL RESULTS VARY. BIRLL IS A WELLNESS PRODUCT, NOT A MEDICAL DEVICE, AND NOTHING ON THIS PAGE IS MEDICAL ADVICE — TALK TO YOUR CLINICIAN ABOUT YOUR RESULTS.

Measured, in one place

Put the evidence to work.