Physique & body fat API

Physique & body fat

POST /v1/body · $0.01 a call

Send a front or side photo of one adult in fitted clothes, shorts or a swimsuit. A vision model grades visible cues on fixed anchor scales: abdominal definition, vascularity, muscle separation and development per group, symmetry and posture. The body fat range and physique score are then computed from published visual reference charts and a fixed formula, so the same cues always give the same numbers. Add height and weight for a second, BMI-based body fat estimate.

For physique raters, ai gym coaches, body transformation trackers.

Request

Send the photo as image (multipart), image_base64 or image_url, as described in the overview. These optional fields go alongside it:

Field	Type	Description
`context`	string, up to 500 characters	Anything the user adds, e.g. "just woke up, flexed" or "6 months of training".
`sex`	one of male, female	Picks the body fat reference chart. Taken from the photo when missing.
`age`	number, 18 to 100	Years. Used by the BMI-based estimate (default 30 when height and weight are given without it).
`height_cm`	number, 100 to 250	With weight_kg, adds a second body fat estimate from BMI (Deurenberg formula).
`weight_kg`	number, 30 to 300	With height_cm, adds a second body fat estimate from BMI.
`goal`	one of cut, bulk, recomp, maintain	Adds a goal-specific note to the training focus.

Photo tips. One adult, front view, standing straight in even light. Shirtless, a fitted top or swimwear, with the waist visible. Full body if you want legs scored.

curl https://ourapi.keronlabs.com/v1/body \
  -H "Authorization: Bearer $FORKCAST_KEY" \
  -F image=@physique.jpg \
  -F sex="male"

Response

Field	Description
`summary`	One line for a list view, e.g. "Physique 75/100 (Advanced), est. body fat 12 to 15%".
`physique_score`	0 to 100. 45% muscle development, 30% leanness against an athletic range, 10% symmetry, 15% posture.
`level`	Beginner (<35), Novice (35+), Intermediate (50+), Advanced (65+) or Elite (80+).
`score_breakdown`	Each part of the score on 0 to 100.
`body_fat`	estimate, low and high in %, the visual range, the BMI-based estimate when height and weight were sent, and which reference chart was used.
`muscles`	shoulders, chest, arms, back, core, legs: score 1 to 10, or null when not visible.
`strongest / weakest`	The highest and lowest scored visible groups.
`v_taper`	Waist to shoulder width ratio and a category: strong, moderate, slight or none.
`posture`	Posture issues seen, with severity mild, moderate or severe.
`training_focus`	Plain suggestions for the weakest groups and notable posture issues.
`confidence`	0 to 1. Lower for loose clothing, back views, poor light or few visible groups.
`warnings`	What limited the estimate and how to take a better photo.

Example

Output of this API's own code on a sample photo. Values will differ for your photos.

{
  "metadata": {
    "id": "req_9cf4da08fe7f40dab71a",
    "engine": "body",
    "status": "success",
    "cached": false,
    "credits_used": 1,
    "created_at": "2026-10-19T09:30:00.000Z",
    "processing_ms": 3400
  },
  "summary": "Physique 75/100 (Advanced), est. body fat 12 to 15%",
  "physique_score": 75,
  "level": "Advanced",
  "score_breakdown": {
    "muscle": 53,
    "leanness": 100,
    "symmetry": 78,
    "posture": 90
  },
  "body_fat": {
    "estimate": 13,
    "low": 11.5,
    "high": 14.5,
    "method": "visual",
    "visual": {
      "low": 11.5,
      "high": 14.5,
      "mid": 13
    },
    "bmi_based": null,
    "reference_chart": "male"
  },
  "muscles": {
    "shoulders": {
      "visible": true,
      "score": 6
    },
    "chest": {
      "visible": true,
      "score": 6
    },
    "arms": {
      "visible": true,
      "score": 6
    },
    "back": {
      "visible": false,
      "score": null
    },
    "core": {
      "visible": true,
      "score": 5
    },
    "legs": {
      "visible": false,
      "score": null
    }
  },
  "strongest": [
    "shoulders",
    "chest"
  ],
  "weakest": [
    "core"
  ],
  "symmetry": 8,
  "v_taper": {
    "waist_to_shoulder_ratio": 0.76,
    "category": "moderate"
  },
  "posture": [
    {
      "issue": "rounded_shoulders",
      "severity": "mild"
    }
  ],
  "training_focus": [
    "Add weighted crunches or cable crunches and hanging leg raises, 2 to 3 times a week."
  ],
  "confidence": 0.85,
  "warnings": [],
  "disclaimer": "Visual estimates for fitness tracking only. Not a medical assessment. For an accurate body fat number use DEXA or a similar measurement."
}