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People are encouraged to reduce their consumption of animal proteins in favour of plant sources to improve food sustainability. This transition from animal to plant sources involves a moderate reduction in protein intake, which can impact eating behavior and, in particular, lead to a compensatory increase in food intake. A reduction in protein in diets characterises various models of eating behaviour change. In rodent models, compensatory hyperphagia is associated with an obesity risk. However, laboratory results suggest that the occurrence of hyperphagia could be modulated by the characteristics of the protein ration, more specifically by the quality of the protein sources and the frequency of consumption of these sources. In humans, this response has yet to be characterised. The aim of this thesis is to better characterise the behavioural response to a reduction in protein intake. In light of the challenges posed by the shift towards plant-based diets, this objective aims to better understand and prevent the obesity risk potentially associated with the protein transition. The thesis is divided into two main questions: in humans, the aim is to better understand the determinants of protein consumption, particularly dietary choices made according to the food environment and available protein sources; in rats, the aim was to modulate the compensatory adaptive response previously observed, in particular by studying the influence of the quality of protein sources (AAI and AANI composition) and their frequency of consumption (rate of protein intake over a week) on the induction of compensatory hyperphagia in response to variations in protein intake. Three studies were conducted in humans. The first focused on the integration of protein into the diet. It showed a link between the value attributed to proteins by individuals and protein consumption. A second study looked at the influence of the protein content of a new food on its perception as a protein source and its integration into the diet. The protein content of the food did not impact the perception of the product or the food associations made. The third study investigated the consequences of a low-protein diet on food consumption.The change in eating behaviour observed seems to be more related to the enjoyment of meals than to their protein content. Two studies were conducted on rats. The overall objective of these studies was to evaluate strategies that would reduce the protein content of the diet without causing hyperphagia. Two strategies were considered: modulating the quality of protein sources or modulating their frequency of intake. Weekly consumption of a high-protein diet did not permanently limit hyperphagia, although its consequences were partially mitigated. In terms of quality, the addition of certain amino acids suspected of being involved in the regulation of protein intake delayed hyperphagia in response to the reduction in protein in the diet, without eliminating it in the longer term.In conclusion, these results show that food preferences are a major determinant of food choices in humans. This determinant makes it difficult to study the effect of protein reduction on eating behaviour in interventions and should be taken into greater account in future studies. In rats, hyperphagia induced by a reduction in dietary protein appears to be an immediate adaptive response that is difficult to prevent with a one-off protein intake. The mechanisms triggering the hyperphagic response still need to be studied.These studies have provided a better understanding of behavioural responses to protein reduction and have opened up new methodological avenues for future studies. These studies have provided a better understanding of behavioural responses to protein reduction and have opened up new methodological avenues for future studies.