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March 6 ch11 body weight.doc

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Sabina Valentine

March 6 – Ch11 body weight Thermic Effect of Food (TEF) • Energy expended to process food Energy expended in physical activity • Energy cost of movement above basal • Affected by body size, intensity of exercise, and how long activities are performed Genetic Factors Genetic factors account for about 25% of a persons body fat Different ideas have been suggested to explain the impact of genetics on body fat • Thrifty gene theory • Set-point theory • Leptin theory Thrifty Gene Theory • Proposes that a gene (or genes) causes people to be energetically thrifty • Proposes that people with this gene expend less energy than other people and therefore gain weight when food is plentiful • A “thrifty gene” hasn’t been identified Set- Point Theory • Proposes that each person’s weight stays within a small range (set point) • The body compensates for changes in energy balance and keeps a person’s weight at their set point • Explains why dieting may not work. Energy conservation contributes to rebound weight gain Leptin theory • Leptin is a hormone produced by fat cells that causes reduced food intake, reduced weight, decreases body fat • Leptin is controlled by the ob gene • Mutation of the ob gene causes reduced levels of leptin leading to increased food intake and reduced energy output Childhood Factors Environmental factors in childhood can influence: • Food choices • Activity levels • Later adult behaviours Childhood overweight increases the risk of heart disease and premature death as an adult Behavioural Factors • Food choices: the composition of a person diet should remain balanced • Hunger vs. Appetite: appetite, a psychological desire to eat, can cause people to overeat Social Factors Social factors influencing our diet include: • Family or cultural traditions • Holidays and celebrations • Easy access to high-fat foods • Less physically active lifestyles • Societal expectations of the “perfect” body Determining Kilocalories Needs The most accurate ways to determine your energy needs:
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