Starvation occurs when a living thing dies from lack of any food substance essential for life. Essential food substances are called nutrients. They are classified into six groups: carbohydrates, fats, minerals, proteins, vitamins, and water. Nutrients furnish energy for regulating body processes and for building and maintaining body tissues. Plants derive energy from sunlight by means of photosynthesis. Human beings and other animals derive energy from carbohydrates, fats, and proteins contained in food. Plants, humans, and animals require minerals and water. Human beings and animals also require vitamins. If living organisms do not receive required nutrients, they waste away and finally die of starvation.
In humans, the most critical nutrient is water. Death occurs when a person loses 20 per cent of total body water. Environmental temperature may vary the rate of water loss, but most people will be able to live only about a week without water. How long a person can survive without food depends on the person’s supply of body fat. Fat is the body’s most efficient form of stored energy. However, most people can survive only 60 to 70 days without food.
