Health Data Agreement
Version 1.0 · Effective date: To be set on launch
Applies to: Zensus mobile application (iOS, Android)
Legal basis: GDPR Article 9(2)(a) — explicit consent for special category health data
Governing language. This document is written in English and the English version is the original and legally binding version. Translations into other languages are provided for convenience only and are generated by DeepL machine translation. In the event of any inconsistency or dispute between a translated version and the English original, the English version shall prevail.
1. Introduction
Zensus ("we", "us", "our") is a health and nutrition tracking application. To provide its core service, Zensus must collect and process data that falls within the definition of special category data under Article 9 of the UK General Data Protection Regulation (UK GDPR) and the EU General Data Protection Regulation (EU GDPR).
This agreement explains exactly what health data we collect, why we collect it, how it is protected, who else may access it, and your rights over it.
Important — Zensus is not medical advice. Zensus is a nutrition and fitness tracking tool, not a medical device. Nothing in this App — including nutrient totals, fitness scores, progress charts, or any content in the Learn section — constitutes medical advice, a clinical diagnosis, or a treatment recommendation. Always consult a qualified healthcare professional before making significant changes to your diet, exercise routine, or health behaviours, particularly if you have or suspect you have a medical condition. If you are experiencing a medical emergency, contact your local emergency services immediately.
By tapping "I agree" during account setup, you give explicit consent under GDPR Article 9(2)(a) for Zensus to process your health data as described in this agreement, and you acknowledge that Zensus is a tracking tool and not a source of medical advice. This consent is separate from, and in addition to, your acceptance of our Terms of Service and Privacy Policy.
2. What Health Data We Collect
2.1 Dietary Data
We record everything you log about your food and drink consumption, including:
- Calorie intake
- Macronutrients — protein (total, plant, animal, dairy, marine), carbohydrates (total, high-quality, low-quality), fats (total, plant, animal, dairy, marine, saturated, unsaturated)
- Micronutrients — all B vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folate, cobalamin), vitamin C, choline, vitamins A, D, E, K1, and K2
- Minerals — potassium, magnesium, sodium, calcium, phosphorus, iron, zinc, iodine, selenium, copper, manganese
- Fatty acids — EPA, DHA, lauric, myristic, palmitic, stearic acids
- Amino acids — leucine, lysine, methionine
- Dietary fibre (total, soluble, insoluble)
- Water intake
- Your daily nutrition targets
We also maintain a running daily aggregate of your intake across all food logs.
2.2 Body Measurements
We record physical measurements you enter, including:
- Body weight and height
- Body circumferences — neck, chest, waist, hips, biceps (left and right), thighs (left and right), calves (left and right)
- Strength benchmarks — maximum weight lifted for key movement patterns (hinge, leg press, vertical and horizontal pull, vertical and horizontal press, gait)
- Cardiovascular metrics — resting heart rate, VO2 max, ApoB (apolipoprotein B)
We maintain a historical record of all measurements you have entered, so you can view trends over time.
2.3 Exercise Data
We record the exercise sessions you log, including:
- Resistance training — weight lifted, repetitions, estimated one-rep maximum, total volume, rate of perceived exertion, distance, duration, and any personal notes
- Endurance training — distance, speed, maximum heart rate, personal best times, intervals, incline, resistance level, rate of perceived exertion, and any personal notes
2.4 Sleep Data
We record the sleep quality ratings you submit (a score from 1 to 10) against each date.
2.5 Profile and Demographic Data
We record your date of birth and gender, which we use to calculate age-appropriate nutrition targets and to apply demographic presets to your goals. We also record how frequently you exercise and your preferred unit system (metric or imperial).
3. Why We Process This Data
The sole purpose of collecting the data listed in Section 2 is to provide the Zensus health and nutrition tracking service, specifically:
- To display your daily nutrition intake and progress against your targets
- To calculate and update your nutrition goals based on your profile
- To track your physical measurements and exercise capacity over time
- To display trends and progress charts
- To award achievements and calculate leaderboard scores
- To allow you to compare your progress within a team
We do not use your health data for advertising, profiling for third-party commercial purposes, or any purpose not listed above.
4. Legal Basis for Processing
We process your special category health data on the basis of your explicit consent under:
- UK GDPR Article 9(2)(a) — for users in the United Kingdom
- EU GDPR Article 9(2)(a) — for users in the European Economic Area
You gave this consent by tapping "I agree" on this agreement during account setup. We record the date, time, language, and version of the agreement you consented to, along with a confirmation that you acknowledged the English version as legally binding (where applicable).
5. How We Protect Your Health Data
We apply the following technical security measures to your health data:
Encrypted at rest: The following fields are stored using application-level encryption in addition to database-level security:
- Resting heart rate, VO2 max, and ApoB values
- Maximum heart rate recorded during endurance exercise
- All historical measurement values
- Personal notes attached to exercise logs
Not separately encrypted at rest (protected by database-level security and access controls):
- Food log nutrient values
- Body weight, height, and circumference measurements
- Exercise performance data (strength, speed, distance)
- Sleep ratings
- Date of birth and gender
All data is transmitted over encrypted connections (TLS). Access to the database is restricted to authorised backend services and staff. Production health data is never used in development or testing environments.
6. Who Else Accesses Your Health Data
We share your health data with the following third-party processors only to the extent necessary to operate the service:
6.1 Sentry (Error Monitoring)
Provider: Functional Software, Inc. (Sentry)
Purpose: We use Sentry to capture and diagnose application errors. If an error occurs while processing a request that involves health data, Sentry may receive the request context, which can include your user ID and the nature of the operation that failed.
What Sentry does not receive: Your actual health values (nutrient amounts, measurement values, etc.) are not included in error reports.
Data processing agreement: In place.
Location: United States (Standard Contractual Clauses apply for UK/EU users).
6.2 PostHog (Product Analytics)
Provider: PostHog, Inc.
Purpose: We use PostHog to record product usage events — for example, whether a data export was requested, and the size of that export. This helps us understand how the app is used and where it can be improved.
What PostHog does not receive: Your health values (nutrient amounts, measurement values, etc.) are not sent to PostHog. Analytics events contain only metadata (event type, whether you are a premium subscriber, your country code, your platform).
Data processing agreement: In place.
Location: European Union (eu.posthog.com).
6.3 Supabase (Database Hosting)
Provider: Supabase, Inc.
Purpose: Supabase hosts the database in which all of your health data is stored, including food logs, body measurements, exercise records, and sleep ratings.
Nature of access: Supabase provides infrastructure only. Your health data is stored on their servers but is not accessed or used by Supabase for any purpose other than providing the hosting service.
Data processing agreement: In place.
Location: United States (Standard Contractual Clauses apply for UK/EU users).
6.4 Fly.io (Application Hosting)
Provider: Fly.io, Inc.
Purpose: Fly.io hosts the backend application that powers Zensus. All requests from the app — including those that read and write health data — are processed on Fly.io's servers.
Nature of access: Fly.io provides infrastructure only. Health data passes through their servers during processing but is not accessed or used by Fly.io for any purpose other than providing the hosting service.
Data processing agreement: In place.
Location: Fly.io runs your request through whichever of three regions is closest to you: the United States (Ashburn, Virginia — DPF/SCCs), South Africa (Johannesburg — Standard Contractual Clauses; South Africa has no EU adequacy decision), or the United Kingdom (London — UK holds an EU adequacy decision, no additional mechanism required).
6.4a Upstash (Caching)
Provider: Upstash, Inc.
Purpose: Upstash provides the in-memory cache the app uses to avoid recomputing your nutrient totals on every request — for example, your rolling 24-hour and 72-hour nutrient summaries are held here temporarily rather than recalculated from the database each time.
Nature of access: Upstash provides infrastructure only. Cached health data passes through their servers but is not accessed or used by Upstash for any purpose other than providing the caching service. Cached entries expire automatically (typically minutes to hours) and are also used for unrelated technical purposes (rate limiting, short-lived security tokens) that do not involve health data.
Data processing agreement: In place.
Location: United States (Standard Contractual Clauses apply for UK/EU users).
6.5 Mailgun (Email Delivery)
Provider: Mailgun Technologies, Inc.
Purpose: Mailgun delivers transactional emails from Zensus, including your weekly nutrition report. The weekly report contains actual health data — your top foods with their calorie and macronutrient values, your daily average intake for the week, week-over-week changes, and your best day's nutrition figures. This data passes through Mailgun's systems in order to deliver the email to your inbox.
What Mailgun also handles: Account and subscription emails (verification, password reset, subscription notices, account deletion warnings) — these do not contain health data.
You can opt out: You can disable the weekly nutrition report email at any time via Profile → Notifications. If disabled, no health data is sent to Mailgun on your behalf.
Data processing agreement: In place.
Location: United States (Standard Contractual Clauses apply for UK/EU users).
6.6 OneSignal (Push Notifications)
Provider: OneSignal, Inc.
Purpose: OneSignal delivers push notifications to your device. Some notifications reference health categories — for example, a measurement reminder notification includes which measurement types (physical, strength, cardiovascular) are due for an update, and milestone notifications reference your accumulated nutrition points. These details are included in the notification payload sent through OneSignal's systems.
What OneSignal does not receive: Your actual health values (e.g. your weight, calorie intake, or specific measurement readings) are not included in notification payloads.
You can opt out: You can disable push notifications entirely or by category at any time via Profile → Notifications.
Data processing agreement: In place.
Location: United States (Standard Contractual Clauses apply for UK/EU users).
6.6a Google (Firebase Cloud Messaging) — added 2026-10-09
Provider: Google LLC.
Purpose: For Android devices, OneSignal delivers your push notifications via Google's Firebase Cloud Messaging (FCM) — the Android operating system's own push transport, which every push provider on Android relies on to actually reach a device, not a choice specific to Zensus or OneSignal. The same notification payload described under OneSignal above (health categories due for update, accumulated nutrition points — never actual health values) passes through Google's FCM servers as the final delivery hop.
Nature of access: Google provides infrastructure only — FCM's role is message routing and delivery, not reading or analysing the payload for its own purposes.
You can opt out: Same control as OneSignal above — disable push notifications entirely or by category at any time via Profile → Notifications.
Data processing agreement: Google LLC is certified under the EU-US, Swiss-US, and UK-extension Data Privacy Frameworks.
Location: United States (DPF).
9. How Long We Keep Your Health Data
Your health data is stored for as long as your account is active. We do not apply a fixed retention period to health data because the ongoing history of your measurements and food logs is the product — deleting it periodically would remove value the service was built to provide.
When you delete your account, all of the health data listed in Section 2 is permanently deleted from our systems within 30 days. Consent records (proof that you agreed to this document) are retained after account deletion as required by GDPR Article 7.
10. Your Rights
Under UK GDPR and EU GDPR, you have the following rights in relation to your health data:
10.1 Right of Access
You may request a copy of all health data we hold about you at any time via Profile → Privacy → Download My Data. Your data will be prepared and delivered as a downloadable file.
10.2 Right to Data Portability
The data export described in Section 10.1 is provided in a structured, machine-readable format (JSON), so you can transfer it to another service.
10.3 Right to Erasure
You may request permanent deletion of all your data, including your health data, by deleting your account via Profile → Account → Delete Account. After a 30-day grace period (during which you may cancel the deletion), your account and all associated health data will be permanently deleted.
10.4 Right to Withdraw Consent
You have the right to withdraw your consent to health data processing at any time. Because Zensus is a health tracking service, processing health data is fundamental to its operation — it cannot function without it. Withdrawing consent is therefore only possible by deleting your account. Doing so will trigger the erasure process described in Section 10.3.
Withdrawal of consent does not affect the lawfulness of processing carried out before the withdrawal.
10.5 Right to Rectification
If any health data we hold about you is inaccurate, you may correct it directly within the app.
10.6 Right to Lodge a Complaint
If you believe we are processing your health data unlawfully, you have the right to lodge a complaint with your local supervisory authority:
- UK users: Information Commissioner's Office (ICO) — ico.org.uk
- EU users: The supervisory authority in your EU member state
11. Children and Young People
Zensus requires users to be at least 16 years old. We do not knowingly collect health data from anyone under 16. If you believe a child under 16 has provided health data to Zensus, please contact us at support@zensus.co.uk and we will delete the data promptly.
Users aged 16–17 are permitted to use Zensus. In accordance with the UK Age Appropriate Design Code (Children's Code) and EU GDPR Article 8, the following protections apply to all users, including those aged 16-17:
- No behavioural advertising or commercial profiling using health data
- Minimal data collection — only data necessary for the core tracking service
- No third-party data sharing beyond what is described in Section 6 of this agreement
- Your height and weight are never shown to other users through the leaderboard or profile card (see Section 7.1); they are shared only inside a Team you choose to join
- Your age is shown to other users only as a 5-year band, and an "under 18" band is never shown
These rules apply to all users regardless of age, in line with the UK Age Appropriate Design Code's data-minimisation and high-privacy principles.
12. Changes to This Agreement
If we make material changes to the health data we collect or how we process it, we will present you with an updated version of this agreement in the app and ask for your consent again before continuing to process your health data. We will not process health data under a new purpose without first obtaining fresh explicit consent.
13. Contact
For any questions about this agreement or your health data, contact us at:
For our full privacy practices, please see our Privacy Policy.
This agreement is governed by the laws of England and Wales. The English version of this document is the legally binding version.