Map of dietary energy availability per person per day (kcal/person/day) in 2001-2003.
no data <1600* 1600-1800* 1800-2000* 2000-2200* 2200-2400* 2400-2600 2600-2800 2800-3000 3000-3200 3200-3400 3400-3600 >3600*Insufficient
First, we need to define a few terms.
Hunger vs. Malnutrition vs. Undernourishment
Hunger is a condition in which a person's food intake is insufficient to support a productive life. The amount of food intake is measured by dietary energy consumption. The UNFAO suggests 2400 kilocalories of energy per day as a minimum daily energy requirement. Many less developed countries, primarily in Sub-Saharan Africa, do not satisfy this requirement. (See the map above.)
Malnutrition is a condition when your food intake does not satisfy your nutritional needs. It occurs when you don't have enough of certain nutrients. You can eat a plenty and still suffer from malnutrition if you're eating a balanced diet. A lot of people in Africa do not suffer from hunger, but do suffer from malnutrition. This is because their diets consist mainly of cereals (wheat, maize, rice, etc.) and tubers (potatoes, sweet potatoes, etc.), which provide them with sufficient energy but not vitamins and minerals.
Undernourishment can be seen as a subset of malnutrition. It is a type of malnutrition caused by insufficient food intake.
To put it in simpler terms: Hunger is when you aren't eating enough, malnutrition is when you're not eating well, and undernourishment is when you're not eating enough good food.
These two definitions are important and must be remembered by heart:
Food shortage - a situation in which food demand exceeds food supply
Famine - a situation in which food shortage occurs, causing starvation and thus great loss of life
Note that food supply is made of two components: Local food supply and food imports. In some regions, such as Hong Kong, the local food supply is smaller than the food demand, but there is no food shortage because we have food imports.