Ideal Body Weight: Expected weight of a healthy normal individual based on age, sex, and height. Thus, a malnourished person would weigh less than their ideal body weight.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Obesity, Morbid: The condition of weighing two, three, or more times the ideal weight, so called because it is associated with many serious and life-threatening disorders. In the BODY MASS INDEX, morbid obesity is defined as having a BMI greater than 40.0 kg/m2.Anorexia Nervosa: An eating disorder that is characterized by the lack or loss of APPETITE, known as ANOREXIA. Other features include excess fear of becoming OVERWEIGHT; BODY IMAGE disturbance; significant WEIGHT LOSS; refusal to maintain minimal normal weight; and AMENORRHEA. This disorder occurs most frequently in adolescent females. (APA, Thesaurus of Psychological Index Terms, 1994)Body Surface Area: The two dimensional measure of the outer layer of the body.Obesity: A status with BODY WEIGHT that is grossly above the acceptable or desirable weight, usually due to accumulation of excess FATS in the body. The standards may vary with age, sex, genetic or cultural background. In the BODY MASS INDEX, a BMI greater than 30.0 kg/m2 is considered obese, and a BMI greater than 40.0 kg/m2 is considered morbidly obese (MORBID OBESITY).Atracurium: A non-depolarizing neuromuscular blocking agent with short duration of action. Its lack of significant cardiovascular effects and its lack of dependence on good kidney function for elimination provide clinical advantage over alternate non-depolarizing neuromuscular blocking agents.Body Mass Index: An indicator of body density as determined by the relationship of BODY WEIGHT to BODY HEIGHT. BMI=weight (kg)/height squared (m2). BMI correlates with body fat (ADIPOSE TISSUE). Their relationship varies with age and gender. For adults, BMI falls into these categories: below 18.5 (underweight); 18.5-24.9 (normal); 25.0-29.9 (overweight); 30.0 and above (obese). (National Center for Health Statistics, Centers for Disease Control and Prevention)Energy Intake: Total number of calories taken in daily whether ingested or by parenteral routes.Body Composition: The relative amounts of various components in the body, such as percentage of body fat.Energy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Weight Perception: Recognition and discrimination of the heaviness of a lifted object.Body Image: Individuals' concept of their own bodies.Weight Loss: Decrease in existing BODY WEIGHT.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Weight Gain: Increase in BODY WEIGHT over existing weight.Diet, Reducing: A diet designed to cause an individual to lose weight.Body Size: The physical measurements of a body.Birth Weight: The mass or quantity of heaviness of an individual at BIRTH. It is expressed by units of pounds or kilograms.Molecular Weight: The sum of the weight of all the atoms in a molecule.Nitrogen: An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.Nutritional Status: State of the body in relation to the consumption and utilization of nutrients.Organ Size: The measurement of an organ in volume, mass, or heaviness.Eating: The consumption of edible substances.Fetal Weight: The weight of the FETUS in utero. It is usually estimated by various formulas based on measurements made during PRENATAL ULTRASONOGRAPHY.Diet: Regular course of eating and drinking adopted by a person or animal.Infant, Low Birth Weight: An infant having a birth weight of 2500 gm. (5.5 lb.) or less but INFANT, VERY LOW BIRTH WEIGHT is available for infants having a birth weight of 1500 grams (3.3 lb.) or less.Adipose Tissue: Specialized connective tissue composed of fat cells (ADIPOCYTES). It is the site of stored FATS, usually in the form of TRIGLYCERIDES. In mammals, there are two types of adipose tissue, the WHITE FAT and the BROWN FAT. Their relative distributions vary in different species with most adipose tissue being white.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.