Last updated: May 2026
FOUR is a lifestyle app designed to support healthy habits. It is not a medical device and does not provide medical advice, diagnosis, or treatment.
The four rules in FOUR — no liquid calories, no snacking, a 10-hour eating window, and daily exercise — are general lifestyle guidelines. They are not a substitute for advice from a qualified healthcare professional.
Before making significant changes to your diet or exercise habits, particularly if you have an existing medical condition, are pregnant, or are taking medication, consult your doctor or a registered dietitian.
Individual results vary. FOUR makes no guarantees regarding weight loss, fat loss, or any other health outcome.
BMI calculations provided in the app are estimates based on height and weight only. BMI does not account for muscle mass, age, ethnicity, or other individual factors and should not be used as the sole indicator of health status.
Use of FOUR is at your own risk.
FOUR is a habit-forming lifestyle app designed to support fat loss through four simple daily rules. The app is operated by FOUR (© 2026 FOUR).
For any privacy-related questions or requests, contact us at:
beta@four-app.com
We collect the following data when you use FOUR:
Account data: your email address, used to create and authenticate your account.
Profile data: your name, gender, age, and height, provided optionally to personalise your experience and calculate BMI estimates.
Health and behavioural data: your daily rule tracking (which of the four rules you followed each day), weight log entries, and streak history.
Technical data: session tokens and device metadata collected automatically by our authentication provider to keep you securely signed in.
We use your data solely to provide and improve the FOUR app experience:
Your data is stored securely using Supabase, a managed database platform hosted on AWS infrastructure in Europe (eu-central-1 region).
The FOUR app is hosted on Vercel. Neither Supabase nor Vercel have access to your personal data beyond what is required to operate their infrastructure.
We use PostHog for product analytics and session recording. PostHog is hosted on EU infrastructure and processes anonymised usage data only. No personally identifiable information is included in analytics events. Session recordings mask all user input fields. You can opt out by contacting beta@four-app.com.
When payment features are introduced, payments will be processed by Stripe. No payment card data is stored by FOUR.
Your data is retained for as long as your account is active. If you delete your account, all your personal data — including your profile, rule history, weight log, and streak — is permanently deleted immediately. This action cannot be undone.
If you are based in the European Union or Switzerland, you have the following rights regarding your personal data:
Right of access — you can request a copy of the data we hold about you.
Right to erasure — you can delete your account and all associated data at any time from within the app (Profile → Delete account).
Right to rectification — you can update your profile data at any time from within the app.
Right to object — you can contact us to object to any processing of your data.
To exercise any of these rights, contact us at beta@four-app.com and we will respond within 30 days.
FOUR uses browser local storage (not cookies) to cache your preferences and session data on your device. This data never leaves your device and is cleared when you delete your account or sign out.
FOUR is not directed at children under the age of 16. We do not knowingly collect personal data from anyone under 16. If you believe a minor has provided us with personal data, please contact us at beta@four-app.com.
We may update this privacy policy from time to time. When we do, we will update the date at the top of this page. Continued use of the app after any changes constitutes acceptance of the updated policy.
For any privacy questions, data requests, or concerns, contact us at:
beta@four-app.com
We aim to respond to all privacy requests within 30 days.