Evaluate the health consequences of a diet rich in polyunsaturated fatty acids.

a. polyunsaturated fatty acids are preferable to saturated fatty acids;
b. decreases risk of cardiovascular disease;
c. provide (concentrated) energy / can lead to obesity;

In c the students usually gained the mark for contributing to obesity, but the expected health comparison with saturated fats was lacking. Some complicated matters by trying to write at length about cis and trans fats.