Biography
Biography: Yi- Hao Yu
Abstract
It becomes increasingly evident that hedonic overeating plays a very important role in the current obesity epidemic. "Hedonic hunger" denotes a state where the "hunger" is present not because of the need for energy repletion (e.g., 4-6 hours after consuming a regular meal) or due to a long-term energy deficit (e.g., having lost 20 lbs and is recovering from an acute illness), but it is generated by a pure pleasure of ingesting foods even in the presence of energy surplus. A neuronal network responsible for hedonic hunger/overeating is distinguishable from the one that operates on the metabolic signals to replete energy. Hedonic hunger and eating is independent of energy status and is controlled by a different set of signaling molecules. However, hedonic hunger/overeating is not equivalent to weight gain or obesity. There exist strong metabolic mechanisms to maintain energy balance and keep body weight in check. While our "free will" can be an overriding determinant of how much we eat at a given moment (e.g., we may eat twice as much as the usual meal when eating out with friends or in a party) and how much calories we burn at a given time (e.g., we may spend one extra hour in the gym to train for an upcoming competition), we always tend to return to our usual state of energy reserve (i.e., zero net change in energy reserve). Under the normal physiological condition, our body weight, roughly correlated with our energy reserve or fat mass, is amazingly stable over a long time period, despite the constant short-term fluctuations. Because of the strong homeostatic metabolic mechanisms, the day-to-day or week-to-week fluctuation of energy fluxes is rarely consequential in terms of the long term net weight changes. Then, is the hedonic overeating any different from all other causes of short-term fluctuation, or is it a cause of sustained weight gain and obesity? Current data suggest that hedonic overeating in a significant number of people does translate into sustained weight gains and obesity. This form of obesity, i.e., hedonic obesity, is characterized by a consistently elevated metabolic rate that exceeds the normal value expected for a person with the same weight, a distinctive feature from another form of obesity, metabolic obesity. In this presentation, we discuss hedonic obesity in relationship to hedonic hunger, and whether the latter is an obligatory and/or sufficient factor for the development of hedonic obesity.