A "right to food" inherently forces others to work to produce, transport, and supply that food. This is most definitely a form of involuntary servitude, violating the rights of those who produce the food, and recognizing food as a legally binding right could infringe on national sovereignty, leading to unintended policy consequences.
Also, There is no universal definition of what constitutes an "adequate" diet, making it legally difficult to define what constitutes a violation of the right to food.
How would a "right to food" would be enforced, especially in areas with severe scarcity? If the food does not exist or cannot be bought, a legal right cannot make it appear.
What next, a "right to oral sex" ?
A "right to food" is in essence communism. Communism theoretically promises (pipe dreams) to meet all needs, historical implementations have always led to severe food shortages, famine and death (e.g., in the USSR or China).