If you're talking about an online tournament, then sure as long as you can keep your attention and focus since no one would know otherwise.
If you're talking about in person, then it's probably best to stick to snacks or smaller bites as you're playing. Gauge how long you can expect to play if you were to make a long run into the tournament and see if you can eat a bigger meal beforehand to avoid eating at the table if you can't multitask efficiently.