Diet and Energy Sources GapFill

A healthy, balanced diet is important to maintain good health and requires eating a range of nutrients in appropriate quantities to maintain a healthy body weight. 

Nutrients required in large quantities are known as macronutrients, the proportion of which needs to be considered if a healthy lifestyle is to be maintained. The usual recommendation is 45–65% of overall calorie intake to be comprised of   proteinfatsmicronutrientscarbohydrates, as this is used as the major source of energy for physical activity and sport. When the body consumes this type of food, it is broken down into  fatglycogenglucoseATP, which is then used by muscle cells to release energy for exercise in a process called  perspirationhydrolysisevaporationrespiration. However, if there is a sufficient level of glucose in the blood, this type of food is converted to  glycogenlactic acidfatprotein and stored in the muscle and liver, ready to be broken down to glucose when the body needs it.

 FatProteinCarbohydrateMicronutrient intake should be kept below 25–35% of total calorie intake as excessive saturated forms can increase total cholesterol and act as a risk factor for chronic health conditions such as diabetes and heart disease. Nevertheless, this dietary component is still used as a secondary source of energy when physical activity is completed at a low intensity, such as when walking, gardening or performing a light jog, or when  proteincarbohydratephosphocreatinefibre stores are depleted.

 CarbohydrateProteinFatMicronutrient intake is recommended at 10–30% of total energy intake as it cannot be stored in the body, and so the excess is likely to be  excreted in urine. However, it is very important for muscle growth and repair, especially when taken   24 hoursimmediately48 hoursthe morning after resistance exercise.

Water is another important feature of the diet as it helps to maintain hydration. It becomes even more important in physical activity and sport since body water is lost through  thirstrespirationurinationsweating, as the body tries to cool itself down to prevent an excessive rise in body temperature. Inclusion of electrolytes will help retain water and prevent a large amount of it being passed in urine. If dehydration of >2% body mass occurs, performance will be impaired as blood will thicken and heart rate and body temperature will increase, leading to early fatigue. Dehydration of >5% could be dangerous to health and should be avoided. Maintaining hydration will ease the perception of effort and limit an excessive rise in heart rate, utilising a greater percentage of   proteincarbohydratefatenergy rather than the limited store of   proteinfatcarbohydrateenergy for energy.