What is a defining characteristic of unsaturated fats?

Unsaturated fats are defined by the presence of one or more double bonds within their hydrocarbon tails. This structural feature is crucial because it affects the physical properties of the fat. The double bonds introduce kinks into the fatty acid chains, preventing them from packing closely together. As a result, unsaturated fats are typically liquid at room temperature, such as oils. This contrasts with saturated fats, which have no double bonds and are solid at room temperature due to their straight chains that allow for tight packing. Understanding this characteristic is essential when considering the nutritional and health implications of different types of fats in the diet.