Intake and Satiety

The objectives of this section are to indicate

• Satiation is important in the control of nutrient intake.

• Choice of food and taste, pleasure, volume and weight of food, energy density, osmolarity and proportions of nutrients are important dictates of satiety.

• Behavioural and cultural practices can override biological constraints.

The sense of appetite begins with hunger and may end with the feeling of satiety.

Satiation is the inhibition of hunger and eating arising from the eating sufficient food. Satiation is the process that brings a period of eating to a halt. Among the many elements that make for appetite is food and its palatability. Palatability, a complicated sensation to define is a mix of taste and smell. It is a hedonistic evaluation of the food under particular circumstances and cannot easily be measured. It is best perhaps measured with a visual analogue scale in which a line reading from 0 to 10. 0-5 is less than expected, 5-10 more than and it is possible to rank a phenomenon by saying how much it comes less or more than expectations. Palatability is a rating of the pleasure experienced when a particular food is eaten. Salt and sweet foods are usually liked , bitter and sour less so. Palatability has an effect on satiety and food intake.

Satiety is the inhibition of the sensation of hunger and as a consequence the limiting of food ingestion. The amount of food that is eaten should meet the needs of the individual, supplying the metabolic, reproductive and growth processes and will vary with the individual in different phases and energy expenditures of life. There are also strong social and cultural influences on food intake. Eating behaviour may be determined by an interaction between the availability and choice of food, satiation signals and the biological responses to food ingestion.

It is possible to fast, to eat sufficient or to eat in excess of the required or that which is felt to be appropriate or desirable. If there is insufficient money or food available it may be imperative for a mother to reduce her energy intake in order to feed her children. If there is an excess of food available then this may lead to obesity and accumulation of body fat. These extremes of behaviour override the controls of appetite or dietary intake 1. The amount of food eaten should meet the needs of the individual. Nutritional intake is important in supplying metabolic processes which will vary with the individual in different phases and energy expenditures of life. There is also a strong social and cultural influence on food intake.

2. Eating behaviour may be determined by an interaction between the choice of food, and the satiation signals of the biological responses to food ingestion. Choice of food or taste, intensity and pleasure given (hedonistic response), volume or weight of food, energy density, osmolarity and the proportions of macro nutrients are important factors in eating behaviour.

3. There are two approaches to eating behaviour studies: a behavioural approach measures eating patterns and food intake; a quantitative approach measures dietary nutrient and energy intake.

4. The behavioural approach to food intake looks at eating as being organised into meals which are taken at variable time intervals. A meal consists of a series of phases, each controlled by different mechanisms and associated with various emotional states. At least three distinct phases of the meal can be distinguished: meal initiation, meal maintenance, and meal termination. Hunger is associated largely with meal initiation and satiety with meal termination.

5. The controls on food intake include: hunger, cravings and hedonic sensation; energy and macronutrient intake; peripheral physiology and metabolic events, and neurotransmitter and metabolic interactions in the brain.

6. The quantitative approach examines the requirement to eat as continuous or intermittent. The basic vegetative activities which ensure the housekeeping of the body require a continuous provision of energy.

7. No centre controlling satiety has been identified in the brain.

8. The passage of energy-rich food from the stomach to the intestine is regulated. Concentrated solutions empty slowly, whereas dilute solutions empty rapidly, producing the same net delivery of calories to the intestine. Satiety may result from a feeling of gastric distension and high rate of gastric emptying. Following the absorption of food, satiation may follow the storage of the absorbed nutrients.



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