Different fat sources are used for infant formula; vegetable fat sources and animal fat sources, like cow’s milk fat. Cow’s milk fat contains a wider variety of fatty acids, including short- and medium-chain fatty acids, compared to vegetable fats. Furthermore, the structure of the fat sources differ. This research focused on the differences in digestion, absorption, and metabolism after consumption of these different fat sources. In vitro models were used to study the digestion process. No differences were found in total fat digestion, but the type of fatty acids that were released differed between the fat sources. In a human intervention, we studied the absorption and postprandial metabolic responses after consumption of infant formulas with different fat sources. No differences in fat absorption or energy expenditure were found. Interestingly, cow’s milk fat prolonged satiety compared to vegetable fat. Furthermore, this thesis provides insight in the application of breath analysis to use as a non-invasive method to determine metabolic effects of nutrition.