Saturated fatty acids (SFA) and trans-Fatty acids (TFA) and are a major public health issue because they increase the risks of cardiovascular diseases. TFA and SFA are found mainly in solid fats, and form crystalline triacylglycerol. This crystallinity plays an essential role to texture the lipid phase in food products, i.e. to give its solid-like behavior. But public health authorities harden regulations to lower the intake of these solid fats especially TFA. Facing these legislation and health issues, food industry aims at replacing these solid fats by healthier products, but able to solidify the lipidic phase. Oleogels are the most promising and studied substitutes. They consist in vegetable liquid oils (usually healthy), gelled by small molecules called oleogelators. These compounds self-assemble at low concentration in a network of fibrillar aggregates, which provides the mixtures the sought mechanical properties. A few clinical and in vitro studies have been conducted with oleogels, but focus mainly on digestion. They show a decrease of after-meal triglyceridemia and a decrease of the extent of lipolysis during digestion in vitro. These results are encouraging but not enough to assess the benefits of oleogels on health. One needs to address the effects on metabolism, on guts and microbiota. Moreover, the observed effects have not been correlated so far with physicochemical or mechanical quantities. For instance, which properties slows lipolysis: structure of the gel, elastic moduli their surface tension, their solubility which slows digestion? In this context, we have shown that some fatty amides like palmitoylethanolamide gel edible oils. These compounds are endogenous (i.e. naturally present in the body) and have beneficial effects on health. In the corresponding gels, oil is less hydrolyzed during digestion in vitro than when it is liquid. The objective of this proposal are: 1) to synthesize and develop as new oleogelators, endogenous fatty amides, and to study the structure of the formed gels; 2) to know and predict their thermo-mechanical behavior: for this purpose, we will map and model their phase diagrams, measure their complex viscosity, yield stresses and interfacial tensions; 3) to correlate these quantities with the extent of lipolysis; 4) study the impact of oleogels on the physiology and metabolism of the lipids, on the inflammatory response of the guts and on the microbiota. The ultimate goal is to correlate the physiological effects with the thermo and mechanical properties of the gels. We will address these questions in 4 different work-packages. In the first one, we will synthesize a series of endogenous compounds and test their ability to gel rapeseed oil. We will study the structure of the oleogels by electron microscopy, small angle scattering and FTIR. In order to measure the shape and sizes of the aggregates and the intermolecular interactions. In the second work-package, we will select oleogelators with low gel concentrations and we will measure both their rheological properties and map their c-T phase diagrams. The transitions will be studied by rheology, turbidimetry, microDSC, VT-NMR and IR-microscopy experiments. In parallel, the phase diagrams will be modelled by activity coefficient models (NRTL-SAC) or residual approaches (SAFT or PC-SAFT based models). In the third work-package, we will study the rate and extent of the digestion in vitro of the oleogels. The interfacial tension of the gels in the used physiological buffers will be measured. Then, we will identify the thermodynamical, rheological or interfacial quantities impacting the digestion and we will try to correlate it quantitatively with the rate of lipolysis. In the last work-package, we will study in mice the impact of gelation on the lipid metabolism, the gut inflammation and microbiota. The results will be analyzed and correlated with the rheological, structural and thermodynamical properties measured from the previous tasks.