I'll take a stab at this question, though it will be by no means complete. I assume your question relates to food aid given externally. Food aid is given is typically given in times of famine, imminent famine, or some other dire need such as a natural disaster. Here the imperative is moral: to save human lives. Food aid is also given to curry favor with a government of faction, often as part of a larger aid package. There may be some need for food, but the food aid allows resources to diverted to other ends that would normally be used to grow or purchase food. The objective is primarily political, but is couched in humanitarian terms. While food aid appears to a purely good act, it has some negative consequences. For instance, it can destroy local food markets; who can compete with free food? Without the ability sustain itself, a country becomes dependent on food giveaways from another (or others). Some suggest this reflects a hidden objective of countries that donate: to increase markets for their own farmers who are often politically powerful. I'm not aware of any evidence that proves this is what goes on; it may be better explained as a case of good intentions gone awry. Nonetheless, food donors have become much more sensitive to this side effect, and have increasingly sought to restrict food aid until the most necessary circumstances.