Fitbit

Fitbit Body API

Read and write weight and body fat log entries, BMI time series, and body weight / body fat goals. Aria scales and manual logs both flow into this surface.

Fitbit Body API is one of 12 APIs that Fitbit publishes on the APIs.io network, described by a machine-readable OpenAPI specification.

This API exposes 1 machine-runnable capability that can be deployed as REST, MCP, or Agent Skill surfaces via Naftiko.

Tagged areas include Body, Weight, BMI, and Body Fat. The published artifact set on APIs.io includes API documentation, an OpenAPI specification, and 1 Naftiko capability spec.

Documentation GitHub OpenAPI

OpenAPI Specification

openapi: 3.0.3
info:
  title: Fitbit Body API
  description: |
    Read and write body and weight data for Fitbit users: weight logs, body fat
    logs, BMI, body weight goals, and body fat goals. Includes time-series
    endpoints for weight, BMI, and body fat percentage.
  version: '1'
  contact:
    name: Fitbit Developer
    url: https://dev.fitbit.com/build/reference/web-api/body/
servers:
- url: https://api.fitbit.com
security:
- OAuth2:
  - weight
paths:
  /1/user/{user-id}/body/log/weight/date/{date}.json:
    get:
      summary: Get Weight Logs By Date
      description: Retrieves a list of all user's weight log entries for a given day.
      operationId: getWeightLogsByDate
      parameters:
      - $ref: '#/components/parameters/UserId'
      - name: date
        in: path
        required: true
        schema:
          type: string
      responses:
        '200':
          description: Weight logs.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/WeightLogList'
    post:
      summary: Log Weight
      description: Creates a log entry for a body weight.
      operationId: logWeight
      parameters:
      - $ref: '#/components/parameters/UserId'
      - name: weight
        in: query
        required: true
        schema:
          type: number
      - name: date
        in: query
        required: true
        schema:
          type: string
          format: date
      - name: time
        in: query
        schema:
          type: string
      responses:
        '201':
          description: Weight log created.
  /1/user/{user-id}/body/log/weight/{weight-log-id}.json:
    delete:
      summary: Delete Weight Log
      description: Deletes a user's weight log entry with the given ID.
      operationId: deleteWeightLog
      parameters:
      - $ref: '#/components/parameters/UserId'
      - name: weight-log-id
        in: path
        required: true
        schema:
          type: integer
      responses:
        '204':
          description: Weight log deleted.
  /1/user/{user-id}/body/log/fat/date/{date}.json:
    get:
      summary: Get Body Fat Logs By Date
      description: Retrieves a list of all user's body fat log entries for a given day.
      operationId: getBodyFatLogsByDate
      parameters:
      - $ref: '#/components/parameters/UserId'
      - name: date
        in: path
        required: true
        schema:
          type: string
      responses:
        '200':
          description: Body fat logs.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/BodyFatLogList'
  /1/user/{user-id}/body/{resource-path}/date/{date}/{period}.json:
    get:
      summary: Get Body Time Series By Date
      description: Retrieves the user's body data (weight, BMI, or fat) over a period of time.
      operationId: getBodyTimeSeriesByDate
      parameters:
      - $ref: '#/components/parameters/UserId'
      - name: resource-path
        in: path
        required: true
        schema:
          type: string
          enum: [bmi, fat, weight]
      - name: date
        in: path
        required: true
        schema:
          type: string
      - name: period
        in: path
        required: true
        schema:
          type: string
          enum: [1d, 7d, 30d, 1w, 1m, 3m, 6m, 1y, max]
      responses:
        '200':
          description: Body time series.
          content:
            application/json:
              schema:
                type: object
  /1/user/{user-id}/body/log/weight/goal.json:
    get:
      summary: Get Body Weight Goal
      description: Retrieves the user's current body weight goal.
      operationId: getBodyWeightGoal
      parameters:
      - $ref: '#/components/parameters/UserId'
      responses:
        '200':
          description: Body weight goal.
components:
  parameters:
    UserId:
      name: user-id
      in: path
      required: true
      schema:
        type: string
        default: '-'
  securitySchemes:
    OAuth2:
      type: oauth2
      flows:
        authorizationCode:
          authorizationUrl: https://www.fitbit.com/oauth2/authorize
          tokenUrl: https://api.fitbit.com/oauth2/token
          scopes:
            weight: Weight, BMI, and body fat data
  schemas:
    WeightLogList:
      type: object
      properties:
        weight:
          type: array
          items:
            $ref: '#/components/schemas/WeightLog'
    WeightLog:
      type: object
      properties:
        bmi:
          type: number
        date:
          type: string
          format: date
        fat:
          type: number
        logId:
          type: integer
          format: int64
        source:
          type: string
        time:
          type: string
        weight:
          type: number
    BodyFatLogList:
      type: object
      properties:
        fat:
          type: array
          items:
            type: object
            properties:
              date:
                type: string
              fat:
                type: number
              logId:
                type: integer
                format: int64
              source:
                type: string
              time:
                type: string

Fitbit Body API

Documentation

Specifications

Other Resources

OpenAPI Specification