International Journal of Research Available at https://pen2print.org/index.php/ijr/ e-ISSN: 2348-6848 p-ISSN: 2348-795X Volume 06 Issue 2 February 2019 Available online: https://pen2print.org/index.php/ijr/ Page | 397 Biochemical Mechanisms Involved in the Regulation of Appetite and Weight - Review * Augustine Ikhueoya Airaodion 1 , Uloaku Ogbuagu 2 , Abiodun Paul Oloruntoba 3 , Aanu Paul Agunbiade 4 , Edith Oloseuan Airaodion 5 , Ifeoma Pearl Mokelu 6 , Stella Chinonye Ekeh 7 1,2,3,4,6,7 Department of Biochemistry, Federal University of Technology, Owerri, Imo State, Nigeria * 5 Department of Biochemistry, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria Correspondent Author: augustineairaodion@yahoo.com /+2347030204212 Abstract The overwhelming increase in the prevalence of overweight and obesity in recent years represents one of the greatest threats to the health of the developed world and part of the developing world. Among current treatments, gastrointestinal (GI) surgery remains the only approach capable of achieving significant weight loss results with long-term sustainability. As the obesity prevalence approaches epidemic proportions, the necessity to unravel the mechanisms regulating appetite and weight gain have garnered significant attention. It is well known that physical activity and food intake regulation are the two most important factors involved in body weight control. To regulate food intake, the brain must alter appetite. With this realization has come increased effort to understand the intricate interplay between enzymes, gut hormones (such as ghrelin, leptin, cholecystokinin, neuropeptide Y, glucagon-like peptide 1 etc.) and the central nervous system, and their roles in food intake regulation through appetite modulation. This review discusses the biochemical mechanisms involved in the regulation of appetite and body weight, and explores a suite of well characterized and intensely investigated enzymes, anorexigenic and orexigenic gut hormones, and their appetite-regulating capabilities. Indeed, some enzymes (such as fructose–1,6–bisphosphase and protease inhibitor), gut hormones and brain are involved in the perturbation of appetite and body weight. Keywords: Appetite, weight, obesity, hormones 1. Introduction Hunger and satiety are sensations. Hunger represents the physiological need to eat food. Satiety is the absence of hunger; it is the sensation of feeling full. There are several theories about how the feeling of hunger arises [1]. A healthy, well-nourished individual can survive for weeks without food intake, with claims ranging from three to ten weeks [2]. The sensation of hunger typically manifests after only a few hours without eating and is generally considered to be unpleasant. Hunger is also the most commonly used term to describe the condition of people who suffer from a chronic lack of sufficient food and constantly or frequently experience the sensation of hunger. When hunger contractions start to occur in the stomach, they are informally referred to as hunger pangs. Hunger pangs usually do not begin until 12 to 24 hours after the last ingestion of food. A single hunger contraction lasts about 30 seconds, and pangs continue for around 30 to 45 minutes, then hunger subsides for around 30 to 150 minutes [3]. Individual contractions are separated at first, but are almost continuous after a certain amount of time. Emotional states (anger, joy etc.) may inhibit hunger contractions [4]. Levels of hunger are increased by lower blood sugar levels, and are higher in diabetics [5]. They reach their greatest intensity in three to four days and may weaken in the succeeding days, although research suggests that hunger never disappears [6]. Hunger contractions are most intense in young, healthy people who have high degrees of gastrointestinal tonus. Periods between contractions increase with old age [3]. Appetite is the desire to eat food, sometimes due to hunger. Appealing foods can stimulate appetite even when hunger is absent [7]. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain [8]. Appetite has a relationship with every individual's behavior. Appetitive and consummatory behaviors are the only processes that involve energy intake, whereas all other behaviors affect the release of energy [9]. When stressed, appetite levels may