Food, Nutrition and Diet

What is in a balanced diet?

All organisms require food to survive. It provides energy and the raw materials for growth. We take our food in ready-made as complicated organic molecules.  These food molecules can be placed into seven main groups. A balanced diet needs the correct amounts of each of these types of food molecules.

A balanced diet is the correct amount of each food, not simply ‘enough’ food

• Carbohydrates (sometimes referred to as Starch) are required by our bodies as a source of energy. Example of food which carbohydrates can be found in are pasta, potatoes and rice.

• Fats are needed to insulate our bodies and to make cell membranes. They also contain fat-soluble vitamins. Example of food which fats can be found in are cheese, butter, oils and margarine.

• Protein are required for growth and repair. Examples of food which contain protein are meat, fish, eggs and cheese.

• Fibre is important because it allows the muscles in our intestines to move the material along (called peristalsis) and prevents constipation. Fibre is not digested in our diet. Examples of food which contain fibre are wholemeal products e.g. bread, fruit and vegetables.

• Minerals  - different elements, e.g. iron iron is used to make haemoglobin

• Vitamins  - different structures, e.g. vitamin C Vitamin C prevents scurvy

• Water - water all chemical reactions take place in water

The exact amount of each substance that is needed in a balanced diet will vary.  It depends on how old the person is, whether they are male or female and how active they are. For example, teenagers need a high-protein diet to provide the raw materials for growth. You can estimate the recommended daily average (RDA) protein intake for a person using the formula:

• RDA in g = 0.75 × body mass in kg
• There are differences between the sexes because of the time of the growth spurt and due to periods in girls.

This video provides an overview of  balcanced diet

The amount and type of protein is important. Proteins from animals are called first class proteins because they contain more variety of amino acids compared with plant proteins. Some people’s diet may be influenced by other factors than just their daily requirements. Some people may be vegetarians or vegans and some religions require certain diets to be followed. Some people may have to avoid certain foods to prevent them becoming ill.

Macronutrients

Nutrients are substances needed for growth, metabolism, and for other body functions. Macronutrients are nutrients that provide calories or energy. The prefix makro is from the Greek and means big or large, used because macronutrients are required in large amounts. There are three broad classes of macronutrients: proteins, carbohydrates, and fats.

Food Tests

Protein can be tested using the Biuret test. This involves adding the piece of food to a copper sulphate solution with a little sodium hydroxide added. The light blue colour changes to purple if proteins are present.

Fat can be seen to be present in food if a white emulsion (tiny droplets of fat in water) is made after mixing the food with water and ethanol. This is called the alcohol emulsion test.

Carbohydrates come either as starch or sugars. If you add a few drops of iodine to food it will go blue/black if starch is present.

Underweight / Overweight

Reaching and maintaining a healthy weight is important for overall health and can help you prevent and control many diseases and conditions. If you are overweight or obese, you are at higher risk of developing serious health problems, including heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers. That is why maintaining a healthy weight is so important: It helps you lower your risk for developing these problems, helps you feel good about yourself, and gives you more energy to enjoy life. 

Overweight is having extra body weight from muscle, bone, fat, and/or water.

Obesity is having a high amount of extra body fat. Body mass index (BMI) is a useful measure of overweight and obesity.

Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women.

BMI Categories:

• Underweight = <18.5
• Normal weight = 18.5–24.9
• Overweight = 25–29.9
• Obesity = BMI of 30 or greater

Many factors can contribute to a person’s weight. These factors include

• environment
• family history and genetics
• metabolism (the way your body changes food and oxygen into energy)
• behaviour or habits.

Energy balance is important for maintaining a healthy weight. The amount of energy or calories you get from food and drinks (energy IN) is balanced with the energy your body uses for things like breathing, digesting, and being physically active (energy OUT):

• The same amount of energy IN and energy OUT over time = weight stays the same (energy balance)
• More energy IN than OUT over time = weight gain
• More energy OUT than IN over time = weight loss

To maintain a healthy weight, your energy IN and OUT don’t have to balance exactly every day. It’s the balance over time that helps you maintain a healthy weight.

You can reach and maintain a healthy weight if you:

• Follow a healthy diet, and if you are overweight or obese, reduce your daily intake by 500 calories for weight loss
• Are physically active
• Limit the time you spend being physically inactive