Question

An individual who is 5 feet 6 inches tall maintains a 120 pounds weight between age of 25 and 65. This individual requires 8400 kJ per day for basic metabolic activities. For 3 simplicity, assume this individual’s diet consists of 50% fatty acids derived from lipids and 50% carbohydrates. How much food (in kg) this individual consumed over the 40 years’ time period.

Answer 1

Ans. # Total energy consumed in 40 years = Daily requirement x Total days in 40 years

                                                            = (8400 kJ day^-1) x (40 yr x 365 day yr^-1)

                                                            = 122640000 kJ

# Given, 50% energy is obtained from fatty acid (fats).

So, energy derived from fats = ½ x Total energy = ½ x 122640000 kJ = 61320000 kJ

Calorific value of fats = 9.0 kcal / g = 37.656 kJ/ g

Now,

            Required mass of fats = Energy derived from fats / Calorific value of fats

                                                = 61320000 kJ / (37.656 kJ/ g)

                                                = 1628425.75 g

                                                = 1628.43 kg

# Given, 50% energy is obtained from carbohydrates.

So,

energy derived from carbohydrates = ½ x Total energy

= ½ x 122640000 kJ = 61320000 kJ

Calorific value of carbohydrates = 4.0 kcal / g = 16.736 kJ/ g

Now,

            Required mass of carbohydrates =

Energy derived from carbohydrates / Calorific value of carbohydrates.

                                                = 61320000 kJ / (16.736 kJ/ g)

                                                = 3663957.93 g

                                                = 3663.96 kg

# Total food consumed = Sum of (Mass of fats + Mass of carbohydrates)

                                                = 1628.43 kg + 3663.96 kg

                                                = 5292.39 kg