Balanced diet should include macronutrients; micronutrients; water and fibre or Balanced diet should include fats; carbohydrates; proteins; vitamins; minerals; water; fibre

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Correct proportions of macronutrients and micronutrients.

The energy balance equation is the relationship between the energy consumed – measured in calories and the energy expended – also measured in calories. Maintaining a healthy weight requires a balance between energy in and energy out. Too much energy in or too little energy out leads to excess energy being stored as fat. Too little energy in or too much energy out leads to weight loss.

The macronutrients are carbohydrates, fats (sometimes called lipids)and proteins. They are food components that should be eaten in large quantities that are needed because they contain energy that we can use to maintain bodily function.

Carbohydrates

Carbohydrates provide a major source of energy to the body. At rest between 20 and 30% of our energy needs are provided by the breakdown of this fuel, however during high intensity this may increase to over 90%. A lack of carbohydrate in the diet can lead to tiredness and fatigue and poor mental function. Immune system function is dependant on carbohydrate so a lack of this macronutrient in the diet can lead to more frequent colds, respiratory illnesses and other conditions. In athletes ‘over-training’ can occur more readily if CHO requirements are not met. For every gram of carbohydrate approximately 4 kcal of energy can be produced.

Carbohydrates can be broken down into three classifications; monosaccharides, disaccharides and polysaccharides.

• Monosaccharides are single molecules and are therefore the smallest type of carbohydrate (often called Simple Carbohydrates) . Glucose, fructose and galactose are examples of monosaccharides that we find in foods. Glucose is the most commonly known monosaccharide as it is a major fuel during exercise.

• Disaccharides are two monosaccharides joined together (often called Simple Carbohydrates). For example sucrose (sugar) is formed by a glucose and a fructose molecule joined together and lactose (found in milk) is a combination of a glucose and a galactose molecule.

• Polysaccharides are when three or more monosaccharides are joined together (often called Complex Carbohydrates). The most common polysaccharides are;

Cellulose is a combination of thousands of glucose molecules and is the structural component of the cell wall in green plants. Humans’ digestive systems do not contain enzymes that can breakdown cellulose so this is one of the food constituents that make up our dietary fibre.

Starch is the plants storage form of carbohydrate. It is composed of many glucose molecules, but unlike cellulose the bonds between them can be easily broken down so enzymes can do this in the stomach and small intestine. Most of the carbohydrate we get from a diets comes from the starch contained in breads, rice, potatoes, fruits and other foods high in carbohydrate.

Glycogen is a combination of many glucose molecules. Glycogen is found in the meats and fishes that we eat and is the major form of carbohydrate that we store in our bodies. When glucose passes into the blood from the digestive system (following a meal) it is stored in the muscles and the liver.

Fats

Fats are molecules made up of the atoms carbon, hydrogen and oxygen. It is essential to have some fat in the diet as fat is needed:

• As an energy source (at rest approximately 60-70% of energy is created from fat metabolism) and so a reserve of energy can be stored.

• To regulate body temperature in cold conditions by insulating the body.

• To absorb vitamins from the digestive system into the blood.

• To protect vital internal organs from damage by cushioning them during impacts.

• Because every cell in the body is surrounded by a lipid membrane.

• Fats are also used in the manufacture of some hormones that regulate growth and maintenance of homeostasis.

There are different types of fats; ‘good’ and ‘bad’ fats. Some fats are essential for health and it is important that enough of them are consumed, whereas others can be harmful to health so their consumption should be limited.

The link between whether fats are beneficial or harmful depends on their impact on the amount of cholesterol and other fats in the body. Having some cholesterol in the body is essential as it is needed for cell membrane production and other functions. Cholesterol cannot dissolve in water so it must be transported around the body by carriers called ‘lipoproteins’. There are two types of lipoproteins that carry cholesterol; low density (LDL) and high density lipoproteins (HDL).

Too much LDL cholesterol is detrimental to health and is a major risk factor for heart disease and strokes, as the arteries can narrow due to plaques forming in them. Having high levels of HDL cholesterol is beneficial to health and can prevent heart disease.

Proteins

Proteins are molecules made up of a number of ‘building blocks’ called amino acids. Amino acids are made up of carbon, hydrogen, oxygen and nitrogen atoms. Protein is essential because it is the major constituent in muscle tissue, the heart, the liver and the brain.

It is also needed when there is damage to any of the tissues that are made up of proteins. For example it is crucial that athletes eat enough protein when they have damaged their muscles like when they experience delayed onset muscle soreness (DOMS) or when they experience a strain. Proteins are also found in enzymes, antibodies, hormones and haemoglobin so are needed for many processes in the body. Because of the vital roles in the body, protein is not a preferred fuel for maintaining basal metabolic processes or during exercise, so typically only 5-10% of our energy production comes from protein metabolism. However, during starvation or very long duration exercise (+4 hours) amino acid contribution can increase significantly.

Power and strength trained athletes require more protein in their diet to repair damaged muscles after training and for the growth of new tissue so that muscles are stronger.

Vitamins and minerals are micronutrients and they are essential in small amounts for growth, metabolism and other bodily functions. They are not directly used as a fuel, although many of them are needed for assisting in the chemical processes that occur when fuels are broken down.

Vitamins

Vitamins are organic compounds that are essential in small quantities for healthy growth, metabolism, energy production and other physiological processes that are needed for homeostasis.

Fibre

Fibre is the component of foods that we cannot digest. The majority of the fibre we eat is in the form of cellulose as we do not have enzymes capable of breaking this down. Fibre is an essential part of our diet because it helps food pass through the digestive system and can prevent; constipation, irritable bowel syndrome and some cancers. Foods containing lots of fibre are also helpful for those wanting to lose body fat because it is another food that helps us to feel fuller so we tend to eat less at other times throughout the day. Adults should eat between 12 and 24 grams of fibre per day, although some researchers recommend more than this

Optimum Body Weight is being at the right weight for their event i.e. not being too heavy. It is based on a persons stature/height/build and vary for the activities they are involved in for example the long distance runner is lighter than a sumo wrestler.

In an exam question you may be required to analyse why is managing body weight important for a sports performer.

Reasons include:

• Heavier performers would have to carry excess weight which makes performance harder for example in long distance running

• Having correct body weight to energy outlay to complete activity e.g. if performer has excess body weight then they will be expending too much unnecessary energy and will not be able to run as fast.

• To meet weight categories or to maintain optimum weight for example in boxing

The factors affecting optimum weight:

• sex – Men and women have a different body composition, men tend to have more muscles and larger bones.

• height –Taller people are usually, although not always,heavier than shorter people. Sports like Basketball & Netball benefit from this height advantage.

• bone structure - Everybody has a different bone Structure, sometimes referred to as frame size. The denser a bone is the heavier it is.

• muscle girth – the term “muscle weighs more than fat” is often used to explain this however, 1kg of muscle is the same weight and 1kg of fat. What it means is that muscle is denser than fat so 1kg of muscle will take up less space than 1kg of fat; so people with larger muscle mass tend to weigh more.