Our body digests fat by hydrolysis reaction with the required help of both enzyme lipase from pancreas and surfactant bile acid from liver through gallbladder. We focus on the nature of water as a key reactant. In general, water molecules are bonded together through hydrogen bonds to form clusters. Although it is well known that water does not mix with oil, we have found that certain natural alkaline water having very small clusters can mix with triglyceride well by forming an emulsion phase. This state enhances hydrolysis of triglyceride. It is shown for the first time that significant increase in hydrolysis reaction rate occurs with lipase alone and without the presence of bile acid as followed by infrared spectroscopy showing distinct effect. In contrast, regular water that typically has larger cluster size cannot mix well with triglyceride and therefore cannot offer the enhancement. It is believed that the effect at least in part is due to the smallness of water clusters. These results are encouraging for people with insufficient secretion of bile acid that prevents them from eating fat due to liver or gallbladder problems and they also provide new means to simply enhance fat digestion. This is believed to be the first in-vitro demonstration of its kind. Our results suggest that the physical characteristics of water can positively influence the digestive process. Research focused on the water properties in human body reactions is rare and to our knowledge none for the reaction studied here. This kind of research is expected to create new directions in physiological science and related fields in medicinal sciences when we consider the numerous important chemical reactions in human body that involves water.