F. CAUSES & THEORIES OF OBESITY Many different types with many different causes1. Energy Imbalancea.)b.)2. Genetics Imbalancea.) Gene defects are starting to be found ( Example: Leptin)b.)Could account for 70% of an individual’s propensity to gain weight ~ both parents obese, 80% chance for child ~one parent obese, 60% chance for child ~ neither parent obese, 10% chance for childc.) Identical twins raised apart tend to have similar weight gain patterns and to accumulate weight at similar sitesd.)Thrifty Gene Theory: e.) Body Shape ( Somatype) is a heritable trait: -Ectomorph-Mesomorph-Endomorph3. Metabolic Influences (Theories)a.) Set-Point Theory> Each person is “Programmed” to WEIGH a certain amount or to have a particular level of body fat.> If individuals weigh less or more than their “set point”, their body makes adjustments in food intake or BMR.> People become obese because they gave a high “set-point” (Genetic?) b.)Enzyme Theory> The enzyme lipoprotein Lipase (LPL) takes TG from blood to make it available for cell uptake> LPL gets more active when fat cells are “starved”> Obese people have more LPL in adipose than non-obesec.) Energy Regulating Hormones#1. Leptin#2. Ghrelind.) Fat Cell Theory1. Body fat = number of fat cells time the amount of fat in the fat cell2. Childhood overeating causes more fat cells Obese child may have same number as lean adult Obese adult has more fat cells than lean adult -Don’t grow many new fat cells when mature3. Obese who lose weight have same number of fat cells Very “hungry” fat cells May be the reason why gaining weight back is so easye.) Thermogenesis “Brown Fat” Theory Brown fat makes heat from fat, NOT ATP energy Newborns and try hibernators (bears) have a lot of brown fat Obese may have less brown fatf.) Other Metabolic Factors4. Environmental Influences a. f. b. g. c. h.d i.e.
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