Arguably, their poor choices each day are causing suffering to others.  Increased suffering of the additional animals they eat, and increased resources that are required to keep feeding them all the extra food they eat.  This leads to more damage to the environment than a normal person could do on a normal diet. You're right though.  We should have the freedom to do as we choose, but with the case for man made global warming increasing, the deforestation caused by cattle farming combined with the fact that livestock account for something like over 50% of greenhouse gasses IIRC, it's very arguable that obese people should be fined for doing unnecessarily harm to the environment.