ABSTRACT. Obesity has become an alarming public health problem due to its growing epidemic prevalence, the suffering it causes and the burden on health systems. Obesity is a complex, recurrent disease with social and psychological dimensions that affects all countries, all social backgrounds and ages. Obesity can no longer be considered just a consequence of overeating and lack of physical activity; it is a chronic multifactorial disease. The failure of weight loss diets has led to a new approach to energy needs and an in-depth analysis of neuro-hormonal and behavioral responses to weight loss. The current lifestyle has changed the genotype-environment ratio in favor of the “obese” environment. Food not only satisfies an energy / nutritional need but also a symbolic and hedonic one. Eating behavior depends on cognitive, emotional, social, economic and cultural factors, as well as the organoleptic properties of food, being regulated by homeostatic and hedonic mechanisms. Research in recent decades has revealed the anatomical and physiological pathways of energy homeostasis as well as non-homeostatic / hedonic ones. It creates a balance between internal homeostasis (energy and weight balance) and external “homeostasis” in relation to food, entourage and society (non-homeostatic / hedonic control of eating behavior). The reward brain system mediates the motivational “wanting” with the hedonic “liking”. Hypothalamic control of energy balance can be greatly diminished by hedonic / reward limbic systems (which are not under conscious control). Food reward theory states that motivation is the hedonic value (pleasure, palatability) given by food intake and that influences the amount of food and body fat by flexibly adjusting the weight. Effective measures to combat weight gain must start from an integrative multisensory vision of food at both homeostatic and hedonic levels. Therapies must unify homeostasis with reward, cognition, and emotion.

Keywords: obesity; reward system; hedonic eating; public health issue; physiological issues; psychological issues