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Oct 1 - Obesity 2.doc

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Physical Education and Sport
Scott Forbes

Oct 1 – Obesity #2 Chakravarthy and Booth Eating, exercise and thrifty genotypes: 1.) Need for regular physical activity to maintain normal metabolic function 2.) Food abundance + sedentary lifestyle = metabolic derangement Feast or famine.. In hunter gatherer, we would have to do physical activity to get the food If there was an unsuccessful hunt or there was drought, there would be famine There was a rest – physical activity cycle Thrifty Gene Do some physical activity, get some food Then that’s followed by feast- then famine Then there is physical activity – rest Physical activity reduces skeletal muscle TG stores Blood insulin goes down when we do activity, increases when we eat Physical activity decreases insulin sensitivity People who survived more were the ones who could conserve muscle glycogen stores and replenish these stores. If you could replenish the stores, we could undergo more endurance tests Thrifty gene hypothesis • Our genome adapted to an environment lacking in predictable access to food • efficiently use and storage of energy Hunter – gatherer • Humans evolved during Palaeolithic period (2.6 million – 10,000 years ago) • Human genome remained same but our diet and lifestyle are very different • Industrial revolution • Agricultural revolution Daily physical activity required for hunting and foraging for food... survival • Men hunted 1-4 days/week • Women gathered food every 2-3 days • “feast-famine cycle combined with physical activity - rest cycle related to food procurement selected genes for an oscillating enzymatic regulation of fuel storage and usage”. Thrifty store –replenishing glucose and TG. More efficient storage of these and adipose tissues. With thrifty stores, you would have more energy and last through famine. More thrifty storage = more likely to survive through next famine/activity phase until next feast. Famine and activity (essentially simultaneous) – decrease glycogen and TG stores Contracting skeletal muscle increases GLUT4 and AMPK Feast (intake glucose and fat) – successful physical activity (hunt or gather) Then there relatively non physical activity and we start back at the thrifty storage GLUT4 helps transport glucose into the cell With exercise, GLUT4 increases AMPK is a energy marker in the cell If AMPK goes up, it signals that the muscles don't have much energy. AMPK increases the rate of fat oxidation If you have more glucose and essentials, you will be more successful with hunting Strong biological and environmental pressures that oppose food restriction There is a certain threshold of energy expenditure required to maintain healthy function Its isn’t necessarily how much we intake, but the balance of intake vs. Expenditure We need to know what is the minimum amount of physical activity required? Threshold of Physical Activity • Present sedentary lifestyle combined with constant food availability and abundance has led to disruption between gene- environmental interactions Fuel Storage and Metabolism • “thrifty” genes place a high priority on storing and conserving muscle glycogen (provide rapid energy for muscle work and survival) • Liver provides glucose for brain and RBC while skeletal muscle provides glucose for itself • Repletion rates differ for liver vs. Skeletal muscle (<50% @ 4 hours vs complete @1-2 hours in slow twitch) What have we learned from endurance training? Adaptations?
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