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GainOS

iPhone beta · waitlist open

Science-guided training and nutrition. Built around you.

GainOS is an iPhone app with an AI training and nutrition coach: it builds your plan and nutrition targets from your profile, trains with you in Gym Mode with the phone on the bench, reads your Apple Watch and proposes adjustments from your own biofeedback. Nothing is applied without your approval.

Join the waitlistSee how it works

iPhone · Apple Watch optional · Free during the beta · The app is in Brazilian Portuguese

How GainOS is built

  • The AI never blocks the app

    If the AI is down or you have no signal, a scientific engine takes over instantly: Mifflin-St Jeor for energy expenditure. You are never left without a plan, and the app says when the engine built it.

  • Works without signal

    Basement gym? Everything you log stays on the device and syncs when the connection is back. Nothing is lost.

  • Never makes up a number

    No simulated data, no guessed calories. What the AI did not measure, it says it did not measure.

How it works: From your profile to the first workout in minutes

  1. 1

    Scientific onboarding

    Six steps: your body, your experience, where you train, your goal (muscle gain, fat loss, strength, running and more), how you eat and how you live. Injuries become automatic exercise substitutions.

  2. 2

    A plan, with the why

    Training per weekday and macro targets per meal. Every choice comes with its scientific rationale, and a "Basic version" tag when GainOS's standard rules, not the AI, built it.

  3. 3

    Train, log, evolve

    Hands-free Gym Mode, plate photos, Apple Watch workouts. Each analysis may propose adjustments, with the evidence. You approve, or not.

Features: Everything a coach would do. No guesswork.

  • Smart training

    Weekly plan with sets, reps, RIR (reps in reserve) and rest. Swap, add and reorder exercises. The AI keeps your edits.

  • Gym Mode

    One exercise at a time, big buttons, a rest timer that keeps going with the phone locked, voice cues in Portuguese.

  • Nutrition without guilt

    Plate photo, label, barcode or your voice. The app does the math, you correct it. Nothing turns red.

  • Coach

    Ask about training, diet, sleep or recovery. The answer analyzes your data and states the kind and strength of the evidence.

  • Progress & biofeedback

    An analysis that crosses workouts and measurements and proposes adjustments, when you ask and, unless you turn it off, every 4 weeks. It only enters the plan once you tap "Approve".

  • Apple Watch & Health

    HR and calories linked to the workout you logged; HRV (heart rate variability) and VO₂max (aerobic capacity) feed the analyses. Scale, steps and sleep through the Health app.

  • Friends & banter

    Add training partners by email, share a workout day, keep the banter going. Seven badges to earn.

Gym Mode: Full screen, hands free.

Made for the phone on the bench and sweaty hands.

  • One exercise at a time

    Only what matters now: load, reps and what comes next.

  • 56 px buttons

    You can hit them without looking, with sweaty hands.

  • A rest timer that never freezes

    Stays accurate with the screen locked and alerts with a beep, a flash and a spoken cue in Portuguese.

  • Sets pre-filled

    Every exercise opens with your last execution.

  • Swap an exercise

    Search in Portuguese and an animated demo, without leaving the session.

  • Confetti on every set

    Yes, confetti. It respects reduced-motion settings.

Nutrition: Shoot. Speak. Scan. Decide.

Log what you actually ate, without turning food into a grade.

  • Plate photo, item by item

    Rice, beans, meat, salad and the oil nobody sees. Each with its own portion.

  • Label and barcode

    The nutrition table is transcribed, not estimated.

  • Describe by voice

    iOS speech recognition transcribes it, and only the text reaches GainOS.

  • "I'll eat it" or "I won't eat it"

    You decide before anything is logged, seeing the impact on what is left for the day.

  • Targets per meal

    Derived from your plan and today's weight, never from a generic diet.

  • A day above target

    Does not change the weekly average, and the app says so instead of painting it red.

Nutrition estimates carry a margin of error and do not replace a dietitian's guidance.

Apple Watch & Health: Your Watch workout, inside the workout you logged.

Average and max HR and calories land on the same card as your sets and, with HRV and VO₂max, feed the progression analysis.

  • Automatic linking

    The app session and the Watch workout become one record.

  • Runs and rides

    Workouts outside the app join your history, marked as imported.

  • Scale, steps and sleep

    Through the Health app, with weight, body fat and lean mass on your chart.

  • You choose

    Which data the app reads and since when: signup, 30 days, 90 days or everything.

  • Garmin, Oura, Polar and Zepp

    Arrive through their companion apps' Apple Health sync.

  • Nothing is simulated

    No Watch, no data. And nothing invented.

Coach: A coach that shows how strong the evidence is.

For free-form questions, the coach, called Allday in the app, answers in six parts: direct answer, analysis of your data, what the literature recommends, action plan, evidence and next steps.

  • Evidence, without a bibliography

    The answer describes what kind of evidence backs the recommendation, without a list of authors and papers.

  • Weak evidence? It says so

    When the literature is inconclusive, the answer states it.

  • "Why this change?"

    Every suggested change explains the reason and the expected impact.

  • "Approve & Apply"

    Nothing enters your plan without your tap.

Science: Science, not guesswork.

Energy

  • Energy expenditure by Mifflin-St Jeor, with an activity factor from your daily routine. With regular meal and weigh-in logging over two weeks, also from your own results.
  • A calorie floor and a deficit cap of 25 % of maintenance.
  • Below BMI 18.5, the app neither asks for the monthly weigh-in nor runs the monthly progress assessment on its own.

Cardio

  • Zones Z1 to Z5 as bands of your max heart rate, estimated from your age.
  • Readiness computed only from measured signals. The analysis says which signals were missing.

Training

  • Compounds before isolations, larger groups before synergists.
  • RIR as the effort gauge. A deload (a lighter week to recover) when biofeedback asks for it.
  • A declared injury becomes a substitution, never a forbidden exercise in the plan.

In its answers to free-form questions, the coach says what kind of evidence there is and how strong it is, without a bibliography.

Friends and community: Banter, kept up.

  • Friends with consent

    Add by email: weight and workouts only show up once the other side accepts. Then a 1:1 chat with the usual banter.

  • Shared workout

    Send a day of your plan to a friend. They accept it, choose where it fits their week and can edit it before training.

  • Community

    A global chat with an automatic filter for offensive words. Your badges are posted there automatically, under your name, the way you would tell them, and for now this cannot be turned off.

Badges: Seven badges. Criteria in the open.

No points for opening the app. Every badge has an objective criterion, shows your progress while it is missing and, once earned, is yours for good — a week off does not take it away.

  • Training

    Consistent Beginner

    The first workout in your history, logged in the app or imported from Apple Health.

    Log 1 workout

  • Training

    Gym Rat

    Five workouts in your history, of any kind.

    Log 5 workouts

  • Training

    Sacred Monster

    Fifteen workouts. Unshakeable focus, and the app knows it.

    Log 15 workouts

  • Hydration

    Scientific Hydration

    The water target is the one in your nutrition plan.

    Hit the water target for the day

  • Consistency

    Athlete's Mind

    Three messages of yours to the coach, in any mode and in any conversation.

    Send the Coach 3 messages

  • Consistency

    Focus on Progress

    Three measurements on different dates: that is when the chart starts to say something.

    Log your weight 3 times

  • Social

    Progress Club

    A training partner to follow the progress and trade jokes.

    Add 1 friend

  • What about the community?

    Every badge shows what share of the community has earned it. On the early ones, the app tells you that you are among the first. Each new badge also becomes a message on the community wall, posted automatically in your name and visible to all users, with no values such as your weight; today this cannot be turned off.

No badge depends on what you ate: food never enters a score, by design.

Privacy: Your data, no fine print.

  • Plans, coach and analyses are made by AI. Your data goes to the AI provider, which does not use it to train models. Consent is asked for on the waitlist and, in the app, when you create the account.
  • Explicit consent before the first meal or label photo leaves the device, naming who receives it.
  • Meal photos are not kept on our servers. Location is stripped before upload; a thumbnail stays on your iPhone and, after 30 days, is deleted when the app saves a new one.
  • Dictation uses iOS speech recognition. The audio does not reach GainOS servers, only the transcribed text.
  • Coach conversations stay on the server until you delete them. Coach memory comes switched off; if you turn it on, sentences of yours are kept for 60 days to 1 year, depending on the type, unless you repeat them, and you can delete them.
  • Apple Health data only with your iOS permission, for the types and the period you choose. It stays in your account, goes to the AI in the coach and the analyses, and is never used for advertising.
  • Account with email and an argon2id-protected password. Session stored in the Keychain.
  • You delete the account in the app itself, under Você > Configurações > Excluir conta (You > Settings > Delete account), with your password. The server erases your data right away, and so does the iPhone you used; the exceptions are in the policy.
  • Your friends (once either of you accepts the other's request) see your name, your email, your weight and your workouts, including from Apple Health. Your badges become automatic messages on the wall, with your name, visible to everyone.
  • No ads in the app. No cookies or trackers on this site.
Read the full policy

Waitlist: The beta starts soon.

GainOS goes into TestFlight testing soon. Invites go out in small batches: if we open a spot for you, we will email you.

Step 1 of 2: Join the list

Leave your details and, if we open a spot for you, we will email you. The batches are small. The app is in Brazilian Portuguese.

Your phone

We keep name, email, state, country, phone type, the date and your acceptances in a Google spreadsheet to organize the invites; when the invite is sent by email through TestFlight, the email goes to Apple. Details in the privacy policy. This site uses no cookies or trackers.

Once you have the invite

  1. 1Install TestFlight from the App Store.
  2. 2Open the invite on your iPhone.
  3. 3Install GainOS and create your account.

iPhone with iOS 16.4 or later · Apple Watch optional · App in Brazilian Portuguese

What we ask

Use it for two weeks. Tell us what broke, confused you or was missing. The feedback channel comes with the invite.

What you get

Free access for the whole beta and a direct say in what goes into the app.

FAQ: What people usually ask

Is it free?

During the beta, yes. To prevent abuse, each person has AI usage limits, per minute and per day. If you reach one, the app keeps working in a basic version until the limit resets. The model after the beta is not defined yet, and testers will hear first.

When does the beta start?

Soon. TestFlight invites go out in small batches, and joining the waitlist does not ensure an invitation. We give no date because it depends on Apple review — and we would rather not promise what we do not control.

Do I need an Apple Watch?

No. The Watch adds heart rate and calories to your workouts, and HRV and VO₂max to the analyses, but everything else works with the iPhone alone.

Does it work on Android?

Not yet. GainOS is iOS for now. Leave your email on the waitlist and we will tell you if that changes.

Does the AI replace a dietitian, a doctor or a trainer?

No. GainOS organizes training and nutrition based on science, but estimates and suggestions do not replace the guidance of health, nutrition or exercise professionals. If you have a health condition, talk to the professional who follows you before changing training or diet.

What happens to my plate photos?

Before the first photo, the app asks for your consent and says who receives it. The photo goes to the AI provider to produce the estimate, together with the time, the meal's target, your weight, your goal and your dietary restrictions; it keeps it for up to 55 days to prevent abuse and does not use it to train models. It is not kept on GainOS servers, location is stripped before upload, and a thumbnail stays on your iPhone: after 30 days, it is deleted when the app saves a new one. If you prefer not to send photos, manual entry remains available.

Does it work offline?

The whole workout and every log work offline and sync later. The AI needs a connection. When it does not respond, the scientific engine takes over and the app says so; in the coach, that note only shows until you close the app. Without internet, your question to the coach stays in the conversation, unanswered; while the app is open, just tap Try again.

I have a Garmin, Oura, Whoop, Fitbit or Samsung. Does it work?

GainOS reads Apple Health. Garmin Connect, Oura, Polar Flow and Zepp write workouts and heart rate there, so they work. Whoop writes part of the data. Fitbit needs a bridge app. Samsung Health does not sync with iOS.

Which language?

Brazilian Portuguese, from onboarding to the coach. English is not available in the app yet: only this site is in English.

How do I delete my account?

In the app itself: under Você > Configurações > Excluir conta (You > Settings > Delete account), with your password and a final confirmation. It cannot be undone. Right away, the server erases the account and what it keeps about you, and the iPhone you deleted it from erases its local copy; on another iPhone with the same account, delete the app. What stays: usage statistics with no link to you; the text of your limitations in the exercise cache, for up to 30 days; the technical logs the hosting provider keeps; and what the AI provider (up to 55 days) and your friends already received. The policy has the full list. Deleting in the app does not reach the waitlist: to take your sign-up off it, ask through the contact email.