No, it could NOT be advertised as FAT FREE, because fatty acids are lipids (fats), so the advertisement would be false. The reason why being simple- lipids are fats, and so are fatty acids. It would have you end up eating something that you thought that was healthy.
A food product that comprises fatty acids and glycerol can never be considered as a fat-free component. This is due to the fact that both fatty acids and glycerol are the constituents of fats that are also called triglycerides. The mentioned advertisement could be misleading as the products of food containing fatty acids and glycerol can never be fat-free, and the food products comprising fat can never be in the absence of triglycerides as triglyceride is another term for a molecule of fat.
