This lesson covers:
- Why we need energy from food
- Health issues from too much or too little energy intake
- Calculating basic energy requirements
Why our bodies need energy
Our bodies require a steady flow of energy to function properly, which is obtained from the food we consume so it’s crucial to eat a balanced diet.
Energy is required for:
- Brain and nerve function – To process information and control the body.
- Muscle contraction – To allow movement.
- Maintaining body temperature – To keep a stable internal environment.
Health consequences of energy imbalance
An imbalance in energy intake can lead to various health issues.
It’s essential to maintain an energy balance to support overall health.
Consequences of surplus energy intake
- Obesity – It leads to unnecessary fat accumulation.
- Raised disease risk – Diseases like diabetes and heart disease are more likely due to excessive fat.
Consequences of insufficient energy intake
- Impaired growth and development in children – This affects physical and mental capabilities.
- Increased infections – A weakened immune system makes the body more susceptible to illness.
- Irregular menstrual cycles in biological females – This affects reproductive health.
- Nutrient deficiency diseases – Diseases like scurvy (vitamin C deficiency) and rickets (vitamin D deficiency) are more common.
Different energy requirements
The amount of energy an individual needs daily varies depending on several factors, including body size and composition.
- Activity level – The more active you are, e.g. if you’re an athlete, the more energy you need.
- Age – Teenagers often need a lot of energy because they’re growing, whereas elderly people need less.
- Pregnancy – Pregnant people need more energy because the baby growing inside them requires a lot of energy.
- Body mass – The bigger you are the more cells you have and each cell requires energy.
Calculating basic energy requirements (BER)
The basic energy requirement (BER) provides an estimate for the energy needed for bodily functions at rest
The BER formula is:
BER (kJ/day) = 5.4 × 24 hours ×mass (kg)
As body mass increases, the BER also increases, as a larger body has more cells that need energy.
Additionally, extra energy is required for any physical activity undertaken throughout the day.
Worked example – Calculating basic energy requirements (BER)
Calculate the BER for a person weighing 60 kg.
Step 1: Equation
BER (kJ/day)= 5.4 × 24 hours × mass (kg)
Step 2: Substitution
BER (kJ/day) = 5.4 × 24 × 60
Step 3: Correct evaluation
BER = 7,776 kJ/day
Practice Quiz
1. Why do we need energy from food?
Answer: We need energy from food to power various bodily functions such as brain and nerve function, muscle contraction, maintaining body temperature, and supporting overall metabolic processes.
2. What happens if we consume too much energy?
Answer: Consuming too much energy can lead to obesity, increased risk of diseases like diabetes and heart disease, and other health issues associated with excess body fat.
3. What are the consequences of consuming too little energy?
Answer: Insufficient energy intake can result in impaired growth and development in children, weakened immune system, increased susceptibility to infections, irregular menstrual cycles in biological females, and nutrient deficiency diseases like scurvy and rickets.
4. How is energy from food measured?
Answer: Energy from food is measured in calories or kilojoules. One calorie equals 4.184 kilojoules.
5. What is the basic energy requirement (BER)?
Answer: The basic energy requirement (BER) is the amount of energy needed to maintain basic bodily functions at rest. It varies depending on body mass, age, gender, and activity level.
6. How do you calculate basic energy requirements?
Answer: The BER can be calculated using a formula that takes into account body mass and other factors. For example, a simplified formula is BER = body weight (kg) × 24 (kcal/kg/day).
7. Why is maintaining energy balance important?
Answer: Maintaining energy balance is important to support overall health, prevent obesity or malnutrition, and ensure that the body has enough energy to perform all necessary functions.
8. What are the main sources of energy in our diet?
Answer: The main sources of energy in our diet are carbohydrates, proteins, and fats.
9. How do carbohydrates provide energy?
Answer: Carbohydrates are broken down into glucose, which is used by the body for immediate energy or stored as glycogen in the liver and muscles for later use.
10. How do proteins provide energy?
Answer: Proteins can be broken down into amino acids, which can be used for energy when carbohydrates and fats are insufficient, though their primary role is in growth and repair of tissues.
11. How do fats provide energy?
Answer: Fats are broken down into fatty acids and glycerol, which can be used for long-term energy storage and are important for cell structure and hormone production.
12. What is the role of vitamins and minerals in energy metabolism?
Answer: Vitamins and minerals act as cofactors and coenzymes in metabolic pathways that convert food into energy. They are essential for efficient energy production and utilization.
13. How does physical activity affect energy requirements?
Answer: Physical activity increases energy requirements because the body needs more fuel to support muscle activity and other physiological functions during and after exercise.
14. What are the energy needs of athletes?
Answer: Athletes typically require higher energy intake to support their increased physical activity levels, muscle repair, and recovery processes.
15. How do energy needs change with age?
Answer: Energy needs generally decrease with age due to a reduction in basal metabolic rate and physical activity levels.
16. Why do pregnant people need more energy?
Answer: Pregnant people need more energy to support the growth and development of the baby, as well as changes in their own body, such as increased blood volume and tissue growth.
17. What is the effect of body mass on energy requirements?
Answer: Larger body mass increases energy requirements because a greater number of cells require energy to function and maintain bodily processes.
18. How does muscle mass affect energy expenditure?
Answer: Muscle tissue is metabolically active and burns more calories at rest compared to fat tissue, so individuals with higher muscle mass have higher energy expenditure.
19. What is the thermic effect of food (TEF)?
Answer: The thermic effect of food is the amount of energy expended by the body to digest, absorb, and metabolize food nutrients. It accounts for about 10% of total energy expenditure.
20. What are nutrient deficiency diseases?
Answer: Nutrient deficiency diseases occur when the body lacks essential vitamins and minerals. Examples include scurvy (vitamin C deficiency), rickets (vitamin D deficiency), and anemia (iron deficiency).
21. How does protein-energy malnutrition affect the body?
Answer: Protein-energy malnutrition can lead to muscle wasting, weakened immune function, delayed growth in children, and overall poor health.
22. What are the symptoms of overnutrition?
Answer: Symptoms of overnutrition include obesity, increased risk of chronic diseases, high blood pressure, high cholesterol levels, and insulin resistance.
23. How can you achieve a balanced diet?
Answer: A balanced diet includes a variety of foods from all food groups: carbohydrates, proteins, fats, vitamins, and minerals, along with adequate water and fiber intake.
24. What is the role of fiber in energy metabolism?
Answer: Fiber aids in digestion, helps maintain stable blood sugar levels, and promotes satiety, which can help regulate energy intake and prevent overeating.
25. How do you measure energy intake from food?
Answer: Energy intake is measured by calculating the calories or kilojoules provided by the macronutrients (carbohydrates, proteins, and fats) in the food consumed.
26. What are the recommended daily energy intakes for adults?
Answer: Recommended daily energy intakes vary based on age, sex, and activity level, but generally range from 2,000 to 2,500 calories for adult men and 1,800 to 2,200 calories for adult women.
27. How can you track your energy intake?
Answer: You can track your energy intake using food diaries, nutrition apps, or online calculators that estimate calorie content based on food portions and types.
28. What is the relationship between energy balance and body weight?
Answer: Energy balance is the relationship between energy intake and energy expenditure. Maintaining a balance results in stable body weight, while an imbalance leads to weight gain or loss.
29. What is metabolic rate?
Answer: Metabolic rate is the rate at which the body expends energy to maintain basic physiological functions such as breathing, circulation, and cell production.
30. What factors influence metabolic rate?
Answer: Factors influencing metabolic rate include age, sex, body composition, hormone levels, and physical activity.
31. What is basal metabolic rate (BMR)?
Answer: Basal metabolic rate (BMR) is the amount of energy expended while at rest to maintain vital bodily functions. It accounts for the largest portion of daily energy expenditure.
32. How is BMR calculated?
Answer: BMR can be calculated using formulas that consider factors like age, sex, weight, and height. An example formula for men is BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years).
33. What is the Harris-Benedict equation?
Answer: The Harris-Benedict equation estimates total daily energy expenditure by multiplying BMR by an activity factor that accounts for different levels of physical activity.
34. How can you increase your metabolic rate?
Answer: You can increase your metabolic rate by engaging in regular physical activity, building muscle mass, staying hydrated, and eating small, frequent meals.
35. What is the impact of sleep on energy balance?
Answer: Adequate sleep is important for maintaining energy balance as it regulates hormones that control hunger and appetite, and lack of sleep can lead to increased calorie intake and weight gain.
36. What is the role of insulin in energy metabolism?
Answer: Insulin is a hormone that helps regulate blood glucose levels by facilitating the uptake of glucose into cells for energy production and storage.
37. What is the effect of stress on energy metabolism?
Answer: Stress can affect energy metabolism by altering hormone levels, increasing appetite, and leading to overeating or undereating, potentially causing weight gain or loss.
38. How does hydration affect energy levels?
Answer: Proper hydration is essential for maintaining energy levels as it supports metabolic processes, aids in digestion, and prevents fatigue and decreased physical performance.
39. What is the role of thyroid hormones in energy metabolism?
Answer: Thyroid hormones regulate metabolic rate by controlling how quickly the body uses energy, and imbalances in thyroid hormone levels can lead to changes in weight and energy levels.
40. What is energy density?
Answer: Energy density refers to the amount of energy (calories) in a given weight or volume of food. High energy-dense foods provide more calories in smaller portions, while low energy-dense foods provide fewer calories in larger portions.
41. How can you manage energy intake for weight loss?
Answer: To manage energy intake for weight loss, focus on eating nutrient-dense, low-calorie foods, controlling portion sizes, and increasing physical activity to create a calorie deficit.
42. What is the glycemic index (GI)?
Answer: The glycemic index (GI) measures how quickly carbohydrate-containing foods raise blood glucose levels. Foods with a low GI are digested more slowly and help maintain stable blood sugar levels.
43. What are the benefits of eating a balanced diet?
Answer: Eating a balanced diet provides essential nutrients for overall health, supports energy balance, reduces the risk of chronic diseases, and promotes physical and mental well-being.
44. What is the role of micronutrients in energy metabolism?
Answer: Micronutrients, including vitamins and minerals, are essential for enzyme function, energy production, and the regulation of metabolic processes.
45. How does fiber affect energy intake?
Answer: Fiber helps regulate energy intake by promoting satiety, slowing digestion, and stabilizing blood sugar levels, which can prevent overeating and support weight management.
46. What are the health risks of an energy-dense diet?
Answer: An energy-dense diet, often high in unhealthy fats and sugars, can lead to obesity, increased risk of chronic diseases, and poor overall health.
47. How can you balance energy intake with energy expenditure?
Answer: To balance energy intake with energy expenditure, monitor your food intake, engage in regular physical activity, and adjust your diet and exercise routine to match your energy needs.
48. What is the role of leptin in energy balance?
Answer: Leptin is a hormone that helps regulate energy balance by signaling the brain to reduce appetite and increase energy expenditure when fat stores are sufficient.
49. What is the role of ghrelin in energy balance?
Answer: Ghrelin is a hormone that stimulates appetite, promoting food intake and increasing energy storage, especially during periods of fasting or low energy intake.
50. How can you use technology to track energy balance?
Answer: You can use technology, such as fitness trackers, smartphone apps, and online calculators, to monitor your energy intake, physical activity, and overall energy balance to support health and fitness goals.