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.