Comment by globular-toast

The obvious problem with this is how can it tell how large your meal is or how much butter you put in? I can see it working for fast/junk food, though.

When I learnt machine learning one of the things was continually training the model. Like your spam filter. You show it what is spam and eventually it learns. Is this stuff continually trained on the user's BMI? That's the only way to tell if a diet is working. Or is it just making absolute claims based on universal training data?