Hey Shubham

Fats are oxidised in respiration usually during the germination of fatty seeds.When fats are the respiratory substrates, the value of R.Q. becomes less than one because the fats are poorer in oxygen in comparison to carbon and they require more O2 for their oxidation .
R.Q. = Vol. of CO2/ Vol. of O2 = 102/145 = 0.7 (less than one)