💬 FitAPI — Conversational AI Fitness & Nutrition Coach

Stop building fitness logic from scratch. FitAPI gives your app instant access to a conversational AI fitness coach — personalized workout plans, nutrition advice, multi-turn coaching conversations, and structured training programs — all via simple REST calls.
One API replaces months of fitness algorithm development, nutritionist consultations, and training program design.

⚡ Why FitAPI

Alternative	Problem
Build it yourself	⚠️ Months of development — exercise databases, macro formulas, periodization logic, nutrition science — before writing a single feature
Hire a nutritionist/trainer consultant	⚠️ Expensive, slow, not scalable — can't serve thousands of users with personalized plans simultaneously
Static workout databases	⚠️ Generic templates that ignore the user's age, injuries, equipment, and goals — users churn because plans don't fit
Other fitness APIs	⚠️ Exercise lists only — no coaching, no conversation, no plan generation, no nutrition guidance
FitAPI	✅ Conversational coaching + structured plans in one API — personalized per user, clean JSON, ready in minutes

🛒 The Problems FitAPI Solves

Problem	Without FitAPI	With FitAPI
Fitness app onboarding	❌ Generic starter plans that don't match the user's body, goal, or equipment — low engagement, high churn	✅ One call to /v1/chat generates a fully personalized program from the user's profile
Conversational coaching	❌ Static FAQ pages and pre-written tips — users can't ask follow-up questions or get adjusted advice	✅ Multi-turn chat with full history support — users get real back-and-forth coaching in your app
Nutrition guidance	❌ Hardcoded TDEE calculators with fixed multipliers — wrong for most users, no diet-type support	✅ Precise macro targets, meal timing, food recommendations — all from a single coaching message
Structured plan generation	❌ No way to generate a full multi-week program with sets, reps, rest times in structured JSON	✅ /v1/plans returns a fully structured training or nutrition plan ready to render in your UI
Personal trainer tools	❌ Trainers writing programs manually for each client — hours per client, not scalable	✅ Generate a starting program instantly, trainer reviews and adjusts — 10x faster client intake
Health & wellness platforms	❌ Separate vendors for workouts, nutrition, and coaching — integration overhead, inconsistent UX	✅ Chat + plans + health check from one API with consistent JSON response structure
Gym management software	❌ No way to offer personalized plans at scale without hiring staff per member	✅ Serve personalized coaching to every member automatically at signup or check-in

🛠️ Endpoints

✅ POST /v1/chat

Send a message to the AI fitness coach and receive personalized coaching advice. Supports multi-turn conversations by passing history. Pass the user's profile (age, goal, fitness level, equipment, injuries) for more personalized responses. Returns a coaching message, response ID, and token usage.

POST /v1/chat

{
  "message": "Create a 4-day push-pull split for building muscle",
  "user": {
    "age": 25,
    "goal": "muscle_gain",
    "fitness_level": "intermediate",
    "equipment": ["barbell", "dumbbells", "cables"],
    "days_per_week": 4
  }
}

Response:
{
  "id": "fitapi_a3b2c1d0",
  "coach": "Alex",
  "message": "Here's your 4-day Push-Pull Split...\n\nDay 1 - Push (Chest/Shoulders/Triceps):\n• Barbell Bench Press — 4x6-8\n• Overhead Press — 3x8-10\n• Cable Flyes — 3x12-15\n...",
  "usage": {
    "input_tokens": 312,
    "output_tokens": 480
  },
  "latency_ms": 1240
}

✅ POST /v1/chat (Multi-turn)

Continue a coaching conversation by passing the history array. The coach remembers what was discussed and gives contextual follow-up advice — just like a real trainer.

POST /v1/chat

{
  "message": "Can I do this on 3 days instead of 4?",
  "user": {
    "goal": "muscle_gain",
    "fitness_level": "intermediate"
  },
  "history": [
    { "role": "user", "content": "Create a 4-day push-pull split" },
    { "role": "assistant", "content": "Here's your 4-day push-pull split..." }
  ]
}

Response:
{
  "id": "fitapi_b4c3d2e1",
  "coach": "Alex",
  "message": "Absolutely — here's how to compress it into 3 days without losing results..."
}

✅ POST /v1/plans

Generate a complete multi-week training or nutrition plan in structured JSON format. Returns a fully structured plan with days, exercises, sets, reps, rest times, and nutrition targets — ready to render directly in your app's UI without any parsing.

POST /v1/plans

{
  "plan_type": "workout",
  "weeks": 4,
  "user": {
    "age": 28,
    "goal": "muscle_gain",
    "fitness_level": "intermediate",
    "equipment": ["barbell", "dumbbells"],
    "days_per_week": 4
  }
}

Response:
{
  "id": "plan_x9y8z7w6",
  "coach": "Alex",
  "plan": {
    "name": "4-Week Intermediate Hypertrophy Program",
    "weeks": 4,
    "days_per_week": 4,
    "schedule": [
      {
        "day": "Monday",
        "focus": "Push — Chest & Shoulders",
        "exercises": [
          {
            "name": "Barbell Bench Press",
            "sets": 4,
            "reps": "6-8",
            "rest_seconds": 90,
            "tip": "Retract scapula before unracking"
          }
        ]
      }
    ]
  }
}

✅ GET /v1/health

Service health check. Returns API status, version, and timestamp. No authentication required. Use this to verify connectivity before your first integration call.

GET /v1/health

Response:
{
  "status": "ok",
  "service": "FitAPI",
  "version": "1.0.0",
  "timestamp": "2026-06-14T10:00:00Z"
}

💡 Common Use Cases

📱 Fitness & Workout Apps

At user signup, collect age, goal, fitness level, and equipment. One call to /v1/chat generates a full personalized program. Use /v1/plans for structured JSON you can render directly as a weekly schedule UI. Pass conversation history for ongoing coaching as users progress week to week.

🥗 Nutrition & Diet Apps

Ask the coach for macro targets, meal timing advice, and food recommendations via /v1/chat. Use /v1/plans with plan_type "nutrition" to generate a structured multi-week eating plan. Complete nutrition coaching feature in one or two API calls.

🏢 Personal Trainer Platforms

Trainers spend hours writing programs for each new client. Use /v1/plans at client intake to generate a starting program in seconds. The trainer reviews and tweaks — cutting intake time from hours to minutes. Use /v1/chat to answer client questions between sessions automatically.

🏥 Corporate Wellness Platforms

Offer personalized fitness and nutrition coaching as an employee benefit. Every employee gets a coach matched to their goals and schedule — not a generic PDF. Ongoing chat support keeps engagement high. No fitness staff required.

⌚ Wearables & Health Trackers

Pull activity data from the wearable and pass it as context to /v1/chat — the coach gives personalized feedback based on actual performance data. Adjust training recommendations automatically as activity levels change week to week.

🎮 Gamified Fitness Products

Use the conversational coach to celebrate achievements, suggest next challenges, and keep users motivated. Generate new workout plans via /v1/plans as users level up from beginner to intermediate to advanced. Dynamic progression powered by real AI coaching.

🛒 Supplement & Sports Nutrition Stores

Add a free AI coach to your store. Users chat about their goals, get macro targets and supplement recommendations — and see which of your products fit their needs. Direct integration between AI coaching and your product catalog.

📥 Input Fields Reference

/v1/chat

Field	Type	Required	Notes
message	string	✅ Yes	The user's fitness question or request. Max 2000 chars.
user.age	integer	❌ Optional	13–100. More context = better coaching.
user.goal	string	❌ Optional	weight_loss, muscle_gain, endurance, general_fitness, athletic_performance
user.fitness_level	string	❌ Optional	beginner, intermediate, advanced
user.equipment	array	❌ Optional	e.g. ["barbell", "dumbbells", "pull-up bar"]
user.days_per_week	integer	❌ Optional	1–7
user.injuries	array	❌ Optional	e.g. ["lower back pain", "left knee"]
user.dietary_restrictions	array	❌ Optional	e.g. ["vegetarian", "gluten-free"]
history	array	❌ Optional	Previous conversation turns for multi-turn coaching. Max 20 turns.
stream	boolean	❌ Optional	Default false. Set true for Server-Sent Events streaming response.

/v1/plans

Field	Type	Required	Notes
plan_type	string	❌ Optional	workout, nutrition, combined. Default: workout
weeks	integer	❌ Optional	1–16. Default: 4
user.age	integer	❌ Optional	13–100
user.goal	string	❌ Optional	weight_loss, muscle_gain, endurance, general_fitness, athletic_performance
user.fitness_level	string	❌ Optional	beginner, intermediate, advanced
user.equipment	array	❌ Optional	e.g. ["barbell", "dumbbells"]
user.days_per_week	integer	❌ Optional	1–7
user.dietary_restrictions	array	❌ Optional	e.g. ["vegetarian", "gluten-free"]

⚡ Performance

Built on Cloudflare Workers edge infrastructure — deployed globally across 300+ locations. Requests are routed to the nearest edge node to your user automatically.

Endpoint	Typical Response Time	Notes
/v1/chat	1–4 seconds	Conversational coaching response — fully personalized per message
/v1/plans	3–7 seconds	Full multi-week structured plan generation — more output = slightly longer
/v1/health	<10ms	No AI call — pure edge response

Response times reflect AI generation — the API is doing expert-level coaching work in each call, not a database lookup. Results are fully personalized per request.

📊 Plan Comparison

Feature	BASIC $3 🆕	STARTER $29	PRO $79 ⭐	BUSINESS $149
Requests / month	50	1,700	4,600	8,700
Best for	Try the API	Small apps	Growing apps	Production scale
/v1/chat	✅	✅	✅	✅
/v1/plans	✅	✅	✅	✅
Multi-turn history	✅	✅	✅	✅
Streaming support	✅	✅	✅	✅
/v1/health	✅	✅	✅	✅
Overage (per call)	—	$0.003	$0.003	$0.003
Priority support	❌	❌	✅	✅

💡 New to FitAPI? Start with the BASIC plan at just $3/month — 50 requests to test all endpoints and see real results before committing to a larger plan. Upgrade anytime with one click.

Note: Each request to /v1/chat or /v1/plans counts as 1 request. The /v1/health endpoint does not count toward your limit. Overage is charged at $0.003 per call beyond your monthly limit (STARTER and above).

🔐 Authentication

All endpoints require your RapidAPI key, passed automatically by the RapidAPI proxy:

X-RapidAPI-Key: YOUR_RAPIDAPI_KEY

No separate signup, no API key management, no OAuth flow. Subscribe on RapidAPI and start making calls immediately.

❌ Error Handling

All errors return a consistent JSON structure with a human-readable message:

{
  "error": "message is required and must be a non-empty string"
}

HTTP Status	Meaning
400	Invalid input — missing required field or value out of range
401	Missing or invalid RapidAPI key
429	Rate limit exceeded — monthly quota reached or too many requests per minute
502	AI service error — retry after a few seconds
500	Internal server error — contact support via RapidAPI messaging

⚠️ Disclaimer

FitAPI generates fitness and nutrition recommendations for general wellness purposes only. Responses are not a substitute for professional medical advice, diagnosis, or treatment. Users with medical conditions, injuries, or specific health concerns should consult a qualified healthcare provider before starting any exercise or nutrition program.

🆘 Support

Questions or issues? Contact us through the RapidAPI messaging system. We respond within 24 hours on all plans.