Gluttony (from the Latin gluttire, meaning to swallow or to gulp down) is not only making a pig of yourself, but it is the inordinate desire to eat or drink more than you need to or should. It is usually associated with a fear or concern that someone else might eat or consume the portion of food before we do.
Eating disorders such as anorexia or bulimia are not gluttony since they are illnesses. Deliberate and conscious overeating just to prevent someone else from having it for their meal is gluttony.
The Romans perfected the sin with their vomitoriums, where the elite could regurgitate their recently consumed meal and start all over again. Fortunately, it was not as popular or prevalent as portrayed in the movies.
Animals will often eat until they throw up, but when human beings do it intentionally and not because they have an eating disorder, it is gluttony.
This vice abhors any type of abstinence or fasting, whether for medicinal or spiritual purposes. The sin also leads to injustice if someone eats more than they need to survive or to satisfy their hunger while depriving someone who truly needs that food.
Unnecessary waste of food is unjust even if it cannot be transported to those who truly need it.