FitnessAI — AI Fitness Coaching for Gyms & Trainers

Overview

FitnessAI is a complete, production-ready web application that enables users to track, analyze, and optimize their health and fitness journey using artificial intelligence. Built with Next.js 15, React 19, and TypeScript, this application provides a seamless experience for logging food and exercise through natural language or images, receiving personalized AI coaching, and gaining insights into metabolic health. The platform features a modern, responsive design and includes everything needed to run a health management SaaS business, from user authentication to payment processing.

⚠️ Important: External API Costs Disclaimer

Please note that this application requires external API services to function, and you will incur costs based on your usage of these services.

This application integrates with several third-party services that charge fees based on usage:

• OpenAI-Compatible AI Models – Charges per API request for AI-powered parsing, chat, and analysis. Costs vary based on the AI model used and the number of tokens processed. You can use OpenAI, Anthropic, or any OpenAI-compatible endpoint. You pay directly to your chosen AI provider for each API request.
• Stripe – Charges a transaction fee of 2.9% plus $0.30 per successful payment transaction when users purchase subscriptions.
• MongoDB – Free tier available for development with 512MB storage. Production use may require a paid plan based on storage, bandwidth, and usage. MongoDB Atlas offers a free tier suitable for small applications. Check MongoDB Atlas pricing for current rates.

You are responsible for all costs associated with these external services. The purchase price of this application includes only the source code and does not include any API credits, service subscriptions, or usage fees. Before deploying this application, please review the pricing pages of all required services to understand the costs you will incur based on your expected usage volume.

While many services offer free tiers suitable for development and testing, production use will require paid plans. Ensure you have budgeted for ongoing API costs based on your expected user base and usage patterns.

Key Features

AI-Powered Health Logging

Log food and exercise using natural language or images with AI-powered parsing. The application uses OpenAI-compatible AI models to automatically identify and extract nutritional data, exercise metrics, and other relevant information from text descriptions or uploaded photos. The AI parsing system supports multiple food items, exercise types, and automatically calculates calories, macros, and micronutrients.

Natural Language Processing

Users can input health data in natural language, and the AI will automatically parse and extract:

• Food items with quantities and nutritional information
• Exercise types with duration and estimated calorie burn
• Meal timing and exercise timing
• Additional context and descriptions

Image Recognition

The application provides image recognition capabilities for food and exercise logging:

• Upload photos of meals – AI automatically identifies food items and estimates portions
• Upload exercise photos – AI can recognize exercise types and provide context
• Multiple image support – Upload up to 5 images per entry
• Automatic image compression – Images are optimized for efficient processing
• Complete nutritional analysis – Extracted data includes calories, macros, and micronutrients

Comprehensive Health Tracking

Complete health management system with the following features:

• Food Tracking – Log meals with automatic nutritional analysis including calories, macros (carbs, protein, fat), and micronutrients
• Exercise Tracking – Log workouts with automatic calorie burn estimation based on exercise type, duration, and user weight
• Daily Status Tracking – Record mood, stress levels, sleep quality, and sleep duration
• Weight Management – Daily weight tracking with automatic BMR and TDEE recalculation
• Activity Level Tracking – Per-day activity level settings (sedentary, light, moderate, active, very active)
• Health History – View all previously logged entries organized by date
• Data Export – Export health data for backup or analysis

Advanced Metabolic Analysis

Advanced calculations and analysis features:

• BMR Calculation – Automatic Basal Metabolic Rate calculation using Mifflin-St Jeor or Harris-Benedict formulas
• TDEE Calculation – Total Daily Energy Expenditure based on BMR, activity level, and daily exercise
• TEF Analysis – Thermic Effect of Food analysis with AI-enhanced multipliers for protein-rich meals
• Macro Tracking – Real-time carbohydrate, protein, and fat intake tracking with percentage breakdowns
• Calorie Balance – Automatic calculation of net calories (consumed vs. burned vs. TDEE)
• Trend Analysis – Long-term data visualization with charts and insights
• Smart Suggestions – AI-powered personalized recommendations based on 7-day health data patterns

AI Coaching & Expert Consultation

Multiple specialized AI experts available for personalized health coaching:

• General Assistant – Comprehensive health management consultant
• Nutritionist – Registered Dietitian specializing in macronutrient optimization and meal planning
• Exercise Expert – Certified Exercise Physiologist specializing in training program design
• Metabolism Expert – Endocrinology specialist focusing on BMR, TDEE, and TEF optimization
• Behavior Expert – Behavioral psychology specialist for habit formation and behavior change
• Timing Expert (Chrononutrition) – Expert in biological rhythms and meal/exercise timing optimization

Each AI expert features:

• Dynamic Memory System – Each expert maintains independent memory that learns and updates from conversations
• Health Data Integration – AI experts access your complete health history for personalized recommendations
• Multi-Perspective Consultation – Enable multiple experts simultaneously for comprehensive health advice
• Personalized Advice – Recommendations based on your actual health data and goals

Professional Mode

Optional professional mode for enhanced safety and personalization:

• Detailed Health Profiles – Create comprehensive health profiles including medical history, allergies, medications, and family history
• Enhanced AI Safety – AI experts use health profile information to provide safer, more personalized advice
• Lifestyle Information – Track food preferences, restrictions, sleep quality, stress levels, and habits
• Health Awareness – Document health awareness and goal expectations

User Management

Complete user management system with the following features:

• User authentication powered by custom JWT-based system (email/password)
• User profiles with physical metrics (weight, height, age, gender), goals, and preferences
• User dashboard for managing account and viewing statistics
• Health history tracking with date-based organization
• Credit balance management and subscription tracking
• Secure session management with JWT tokens and automatic token refresh
• Password reset functionality with email verification

Credit System

Flexible credit-based pricing system with two subscription plans:

• Train (Free) – 50 credits per month, perfect for getting started
• Transform (Premium) – $9.99 per month, 500 credits per month for advanced features

Credit usage:

• AI Chat – 1 credit per message
• Smart Analysis – 2 credits per analysis

Credits reset monthly (unused credits don’t roll over). All new users start with the free Train plan.

Payment Processing

Integrated Stripe payment system for secure subscription purchases. The application handles checkout sessions, webhook processing, and automatic subscription management upon successful payment. All payments are processed securely through Stripe’s infrastructure.

Pages and Navigation

The application includes the following pages:

• Dashboard (Home) – Main health tracking interface with food/exercise logging, daily summary, weight tracking, activity level, and charts
• Chat Page – AI expert consultation interface with multiple expert roles and dynamic memory
• Summary Page – Comprehensive health data visualization, trend analysis, and historical insights
• Settings Page – User profile management, AI model configuration, professional mode, data export, and account settings
• Pricing Page – Subscription plans and credit purchase
• Profile Page – User account management and health profile configuration
• Login/Register Pages – Secure authentication flows
• Forgot Password/Reset Password Pages – Password recovery functionality
• Subscription Success Page – Confirmation page after successful subscription

Technical Specifications

Technology Stack

• Framework: Next.js 15 with App Router
• Language: TypeScript
• UI Library: Tailwind CSS
• UI Components: Radix UI primitives
• Database: MongoDB with Mongoose ODM
• Authentication: Custom JWT-based authentication system
• Payments: Stripe with webhooks
• AI Integration: OpenAI-compatible API models (configurable base URL and API keys)
• Icons: Lucide React
• Internationalization: next-intl for multi-language support (English, Chinese)
• Charts: Recharts for data visualization
• Date Handling: date-fns for date manipulation
• Form Handling: React Hook Form with Zod validation

System Requirements

• Node.js 18 or higher
• npm or yarn package manager
• MongoDB database (MongoDB Atlas recommended)
• API keys for required services (OpenAI-compatible AI provider, Stripe)
• Email service for password reset (Nodemailer configured)

Deployment Options

The application can be deployed on:

• Vercel (recommended for easy deployment with Next.js)
• AWS EC2 (for more control and custom server configuration)
• Any Node.js hosting platform that supports Next.js

API and Service Requirements

To run this application, you will need to create accounts and obtain API keys from the following services. Some services offer free tiers suitable for development and small-scale production use.

Required Services

OpenAI-Compatible AI Provider

OpenAI-compatible AI models provide the AI capabilities for natural language parsing, image recognition, chat, and analysis. You can use:

• OpenAI (GPT-4, GPT-3.5, etc.)
• Anthropic (Claude models)
• Local models with OpenAI-compatible API (Ollama, LM Studio, etc.)
• Any other OpenAI-compatible endpoint

You will need to configure three separate models in the settings:

• Agent Model – Used for generating health recommendations and analysis
• Chat Model – Used for intelligent conversation features
• Vision Model – Used for image recognition and analysis

Pricing varies based on the provider and model chosen. Check your chosen provider’s pricing page for current rates.

MongoDB

MongoDB handles database storage for user data, health logs, chat messages, and AI memories. MongoDB Atlas offers a free tier with 512MB storage suitable for development and small applications. Paid plans start if you exceed the free tier limits. Visit MongoDB Atlas pricing page for detailed pricing information.

Stripe

Stripe processes credit card payments for subscription purchases. Stripe charges a transaction fee of 2.9% plus $0.30 per successful transaction. There are no monthly fees for standard accounts. Visit Stripe pricing page for complete fee structure.

Email Service (Optional but Recommended)

An email service is required for password reset functionality. The application uses Nodemailer and can be configured with various email providers (Gmail, SendGrid, AWS SES, etc.). Some providers offer free tiers suitable for development.

Installation and Setup

The application includes comprehensive documentation covering:

• Environment variable configuration
• MongoDB database setup and connection
• JWT authentication setup
• OpenAI-compatible API configuration
• Stripe payment setup and webhook configuration
• Email service configuration
• Deployment guides for Vercel and other platforms
• Frontend customization guide
• Pricing and credit configuration
• User guide and feature documentation

All setup instructions are provided in documentation files included with the purchase. The documentation includes step-by-step guides with code examples.

What’s Included

• Complete Next.js 15 application source code
• TypeScript source files
• All UI components and styling (Tailwind CSS)
• API routes: health logs, user profile, AI chat, AI parsing, smart suggestions, TEF analysis, chart data, AI memories, chat messages, authentication (login, register, logout, password reset), Stripe (checkout, subscription management), and model configuration
• MongoDB database models and schemas
• JWT authentication integration
• Stripe payment processing integration
• OpenAI-compatible AI integration (configurable)
• Comprehensive documentation
• Environment variable templates
• Deployment configuration files
• Error handling and validation
• Credit management system
• Health history and storage
• Multi-language support (English and Chinese)
• Professional mode with health profiles
• Dynamic AI memory system

Customization

The application is fully customizable:

• Modify subscription pricing and credit amounts
• Adjust credit costs per AI interaction (default: 1 credit for chat, 2 credits for smart analysis)
• Customize AI expert roles and system prompts
• Modify AI model configurations
• Change color schemes and branding
• Modify UI components and layouts
• Add custom features and functionality
• Customize health tracking fields
• Add additional AI expert roles
• Modify BMR calculation formulas
• Customize chart visualizations
• Add additional languages

Support and Updates

This is a complete, production-ready application. The code follows Node.js best practices and Envato submission requirements. All code is well-structured, documented, and ready for deployment. The application includes comprehensive error handling, input validation, and secure authentication mechanisms.