Diet and Energy

Introduction to Diet and Energy

  • Diet refers to the types and quantities of food that a person consumes.
  • The energy needed by the body is obtained through the metabolism of carbohydrates, fats, and proteins, the three main components found in food.
  • The amount of energy that food provides when metabolised is often measured in kilocalories (kcal) or kilojoules (kJ).

Carbohydrates

  • Carbohydrates are key energy providers. 1 gram of carbohydrate provides 4 kcal (16 kJ).
  • They are broken down into glucose during digestion, which can then be used in respiration to generate ATP, an energy storage molecule in cells.

Fats

  • Fats provide the most energy per gram when metabolised - about 9 kcal (38 kJ).
  • Fats are also important for their roles in hormone production, insulation, protection of vital organs and the absorption of fat-soluble vitamins.

Proteins

  • Proteins yield about 4 kcal (17 kJ) per gram.
  • Although proteins can be metabolised for energy, they are more often used for growth, repair and normal functioning of the body’s cells.

Metabolic Rate

  • Metabolic rate is the rate at which energy is used by the body.
  • It can be affected by a number of factors including amount of physical activity, age, sex, and genetic factors.

Basal Metabolic Rate (BMR)

  • Basal Metabolic Rate (BMR) is the rate at which our body uses energy while at rest to maintain vital functions such as breathing, maintaining body temperature, and heart rate.
  • BMR can also be influenced by factors such as age, sex, weight, and genetics.

Energy Balance

  • A balance needs to be maintained between energy intake from food and energy expenditures (through basal metabolism and physical activity) to maintain healthy body weight.
  • Excess energy is stored as adipose tissue (fatty tissue), leading to weight gain.
  • Negative energy balance (where energy expenditure exceeds energy intake) leads to weight loss.

Consequences of Imbalance

  • Overconsumption of calories, particularly from saturated fats and sugars, can lead to obesity and related health problems.
  • Underconsumption may lead to malnutrition and deficiency diseases.

Role of Dietary Fibre

  • Dietary fibre, while not a source of energy, is crucial for maintaining the health of the digestive system.

Importance of Hydration

  • Water is not an energy source, but is essential for energy metabolism and many other bodily functions.