Skip to content
Andrea Gabutti
Personal use

Bookfits — all-in-one fitness app

All-in-one fitness mobile app (workouts, nutrition, social, AI coaching) for iOS and Android, built solo from the database to the app store release.

Private project — personal use
  • Flutter
  • Dart
  • Node.js
  • Express
  • Prisma
  • PostgreSQL
  • Docker
Bookfits — all-in-one fitness app

All-in-one fitness mobile app for iOS and Android that combines workout, nutrition, physical recovery, AI coaching and a social component into a single product. Freemium model (free + ads, 7-day trial, monthly/annual premium subscription, B2B tier for personal trainers). Stack designed and built entirely solo: Flutter app, Node.js backend, Docker infrastructure, internal admin dashboard.

The problem

Fitness apps on the market specialize in a single area (workout only, nutrition only, tracking only), forcing users to juggle 3-4 different apps that don't talk to each other. Bookfits' goal: a single product covering the entire fitness cycle, with an AI coach that draws on all the data together, not from separate silos.

What it does

Workouts

  • Personalized workout plans, start/complete a session, full history, exercise database with technique tips.
  • Ghost Mode (real-time comparison with the previous session), Adaptive Overload (automatic progression suggestions), Symmetry Score (push/pull/legs/core balance).
  • AI plan generation and exercise substitution, plan sharing via QR code.

Nutrition

  • Meal diary with barcode scanner and Open Food Facts database, daily calorie and macro tracking.
  • Personalized nutrition goals, weekly history, AI-generated meal suggestions.

Stats and progress

  • Body weight, body fat %, measurements and BMI calculator with historical charts, progress photos.
  • Personal records with history, workout calendar, weekly analytics for workouts, weight, cardio and macros.
  • Muscle Heatmap, Recovery Clock, Training DNA, PR Predictor (linear regression on records), CSV export.

AI Coach ("Buck")

  • Personalized chat coach based on the user's real data, AI-generated weekly summary.
  • Lazy Workout: a 5-minute bodyweight session generated on the fly for days with no time.
  • Groq model (Llama 3.3 70B), configurable at runtime from the admin dashboard, no redeploy needed.

Health and wearables

  • Daily steps and active calories synced from HealthKit/Health Connect.
  • Cardio log (distance, duration, activity type) and sleep tracking.

Social and gamification

  • Global leaderboard, follow other users, 1v1 duels with a unique challenge code.
  • Achievements, weekly challenges, workout streaks and habit tracking.

App and subscriptions

  • Home screen widget (streak, calories, water), biometric app lock, local notifications and daily motivational quotes.
  • Freemium model: free with ads, 7-day trial, monthly or annual premium subscription.

Architecture, tech stack and the real engineering problems solved along the way.