from Hacker News

ChatGPT can accurately estimate Body Fat Percentage from photos

by Luc on 5/16/25, 7:13 PM with 11 comments

  • by zerohp on 5/16/25, 7:38 PM

    Methodology doesn't support the conclusion.

    Try using images that it wasn't trained on.

  • by orionsbelt on 5/16/25, 7:47 PM

    I just fed 4o and o4 mini a photo of my torso and gave it my height and asked it to estimate my body weight and body fat %. It was 20-40 lbs too low, so way off.

  • by MostlyStable on 5/16/25, 7:38 PM

    So that is obviously a significant relationship between ChatGPT estimate and the Henselman Guide BFP numbers. But just being a significant relationship doesn't necessarily mean it's useful. I'd bet that BMI (which the author repeatedly mentions is outdated and not very useful), is almost certainly also significantly correlated with BFP values.

    Eyeballing that plot, it looks like ChatGPT estimates are +/- 10%. I'm wondering what the cutoff for usefulness is. I wouldn't' be surprised if BMI is that level of correlated or better.

  • by ulf-77723 on 5/16/25, 8:42 PM

    Dexa is expensive, you can get a modern smart scale for 50€, the cheapest accurate method would be the Caliper tongs.

    What can it be good for? Video surveillance with metadata enrichment? Profiling? Losing body fat takes time. A smart mirror that displays body fat?

  • by BrandoElFollito on 5/16/25, 9:10 PM

    Just by looking at the graph I know that this will be rubbish - because of the line

    When you draw a line this means that your model expects a linear relationship between the variables. Otherwise this is either a feel good line, or incompetence.

  • by OtherShrezzing on 5/16/25, 7:51 PM

    Given the images and text are definitely in the model training set, I'm surprised the results are this inaccurate.

  • by donclark on 5/16/25, 10:01 PM

    Can AI estimate psychological profile based on a photo of the face (face structure)?