Physiological processes of weight loss

    While most people immediately recognize the difficulty of making lasting changes in their habits, the treatment of obesity is generally trivialized.

    In popular belief, it all boils down to exercising willpower: eat less and / or exercise more (Puhl, Moss Racusin & Schwartz, 2007). However, little-known physiological mechanisms triggered by weight-management practices partially thwart dieters' efforts and lead to mistaken and derogatory beliefs about those afflicted with excess weight.

    Intrinsically, weight loss is only achieved by creating an energy deficit in the body (intake <expenditure). Energy intake comes from food consumed, while energy expenditure comes from three sources: physical activity, food thermogenesis (energy used to digest and process food) and basic metabolism (energy used by the body to to stay alive and which represents 60-70% of total energy expenditure (Ravussin, 2002). Thus, there are three ways to lose weight: 1) reduce the amount of food consumed, 2) increase expenditure in energy and 3) modify these two parameters simultaneously, eat less and move more.

    

    Although this notion seems simple, the mechanisms that regulate the energy balance are far from being.

   In addition, the calorie restriction necessary to create an energy deficit sufficient to cause weight loss can be perceived by the body as a threat to its balance. In fact, the body is better suited to defend itself against starvation than against abundance, and the greater the restriction in energy, the greater the body's defense response (Hill, 2002). During calorie restriction, the body first obtains energy from glycogen stored in the liver. He will then look for it in the muscles, organs and fat mass.