Physiological
Physiological factors affect the body’s need and desire for food. If the body is to remain healthy and function correctly it must have adequate amounts of food containing the essential nutrients.

Hunger
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Hunger may be defined as that feeling of emptiness, weakness or pain caused by a lack of food. It becomes more intense as time passes, until we are able to think of little else but food. For those suffering extreme hunger, relieving the body of this pain is the focus of life.
Hunger is controlled by a small gland in the base of the brain called the hypothalamus. The hypothalamus has a number of functions in the body, and works closely with the pituitary gland to: control body temperature regulate appetite, thirst and body fluids induce sleep and wakefulness control the release of growth and sex hormones from various glands throughout the body.
Appetite
Appetite is the desire for food even when the body is not hungry. Appetite can be triggered by the sight of appetising food, the aroma of food in preparation, and even the mention of food in conversation. The hypothalamus registers these cues from the senses and sends messages to the brain which encourage you to think about food. The salivary glands are stimulated and produce extra fluid: your mouth then begins to water. Unlike hunger, if appetite is not satisfied it will eventually go away.

Nutritional requirements
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Many of us select food that is nutritious because we know that we will feel and stay healthy. The food we eat should provide essential nutrients that the body can absorb, and metabolise. There are five different categories for nutritional requirements they are body size/type, age, level of activity, gender and health status.

Body size/type are the nutritional requirements of different sized human bodies vary. Individuals who have larger builds require more nutrients to maintain and operate their body processes. Similarly, those with a smaller body size require less protein for the maintenance and repair of body tissues because their body mass is less.

Age
The human body undergoes specific growth stages throughout life. An infant’s body has an enlarged head, and the arms and legs are short in relation to the rest of the body. Early childhood sees dramatic changes in body proportions. The arms increase in length and muscle tone, which allows for greater movement and coordination, and the legs extend to make up half the body’s height. The period of growth and development continues throughout adolescence until the body attains a more adult form.Because nutrients carry out specific functions within the body, the amount of nutrients needed by an individual is regulated by the growth processes.

Level of activity is determined by an individual who is physically active needs to consume more energy­giving foods than an individual who leads a sedentary (less active) life. A sedentary person requires less of all nutrients than an active person. If an individual consumes large quantities of energy but does not move around much, the body stores the excess as adipose tissue (fat).

Gender
The sex of an individual also determines their nutrient requirements. Biological activities such as menstruation and childbirth mean that women need to have a higher dietary intake of iron and calcium. Men have