On a daily level, malnutrition causes fatigue in individuals, which leads to decreased ability to learn or to perform productive work. This in turn contributes to more poverty which leads to more hunger, and the cycle continues. The cause of hunger is not, ironically, inadequate food or a shortage of arable land on which to grow it. The world has enough land , if properly managed to adequately feed the world's current population. For humans to eat animals at or near the top of the food chain is an ineffiecient use of the planet's resources.
Hunger is the direct result of social and economic causes.
Hunger exists because of inequitable and inadequate distribution of food. In many developing countries, the best farm land is in the hands of a few wealthy landowners. The landowners discourage the latter because they then lose their cheap labor, and cheap labor is necessary to produce cash crops. Ideally, the cash crop brings in enough money to enable people to buy food and the equipment to produce more food. However, the profits are often realized in distant countries, and by only a few people.