I can’t say 100% for sure, but I think it’s assur.
Eating too much in general is probably not a 100% black-and-white issur (even though there are problems with it from a Torah perspective) but this is not the same thing. In that case, you are eating for the sake of eating. You really want to eat the food, and it really is serving a purpose.
In this case, you don’t want to eat the food and you are just “using” it. It seems to me that it’s: 1. being “mevazeh” (disgracing) the food,
and 2. wasting food since you are not eating it for the purpose of eating but only for the purpose of winning a contest.
A Jew is supposed to “eat in order to live”. The purpose of eating is to give us energy to serve Hashem. Even if someone eats unhealthy food, he is still doing it because it is giving him energy (emotional and/or physical) to serve Hashem. If you eat chocolate to have energy to do Mitzvos, then eating the chocolate becomes part of your Avodas Hashem.
But when you stuff yourself for the sake of a contest, you are not eating in order to have energy to serve Hashem. You are “using” the food, and acting like an animal. It is the antithesis of Kedusha and what a Jew stands for.
There used to be an avoda zara that involved stuffing oneself and then going to the bathroom in front of the avoda zara (or something like that). That is what this sounds like to me.