Triacylglycerols or triglycerides (TG\'s) are the main constituents of body fat

Question

Triacylglycerols or triglycerides (TG's) are the main constituents of body fat in humans and other animals. TG's have the highest energy density of the major macronutrients. a) If 15% of the body mass of a 78.5 kg adult consists of TGS, what is the total available fuel reserve, in kJ and kcal, in the form of TG's? Assume energy value of TG's = 37.4 kJ/g 1 KJ 0.239 kcal (1.5 marks) b) The recommended Australian average daily energy intake is 8700 KJ. If daily energy expenditure for this 78.5 kg adult is also 8700 kJ, how long (in days plus hours) can this person survive under starvation conditions when the oxidation of fatty acids stored as TG's are the only source of nutrient energy? (1.5 marks) c) Calculate the weight loss in kg/day under such starvation conditions if the oxidation of fatty acids stored as TG's were the only source of energy? (1.5 marks)

Explanation / Answer

Solution a) Mass of adult = 78.5 kg

15% of total mass is TG = 78.5/100 × 15 =11.775 or 11.76 kg

Therefore total available fuel reserve = 11760 × 37.4 = 439824 kJ/g

Or 11760 × 0.239 = 2810.64 kcal

b) Daily energy intake for a recommended Australian = 8700 kj

Daily Energy expenditure for 78.5 kg adult = 8700 kj

So, the number of days this person can survive under starvation (only source of energy is oxidation of fatty acids) = 439824/8700

=50.55 days approx.

c) weight loss per day under such starvation = 11.76/50.55

=0.23264095 kg/day.

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