Fat makes ice cream taste rich and creamy. Low fat ice creams used to be easily identified by their lack of 'creaminess' and a crunchy ice cream texture, caused by jagged ice crystals forming on freezing.
A special protein from the deep sea pout fish living in the freezing waters of the North Atlantic provided the answer. The pout fish naturally produces its own anti-freeze, an 'ice-structuring protein' which changes the size and shape of ice crystals and lowers the temperature at which they are formed. Using this protein in small amount improves ice crystal formation in low fat ice creams, keeping that 'creamy' texture we love.
So does your ice cream contain fish? No, it doesn't. Once the protein was identified a genetically modified yeast was developed to make it. The protein is then separated from the yeast and purified before being added to low fat ice cream.