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Energy Balance (Not all calories are equal (Quantity v Quality, Desire for…
Energy Balance
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Energy expenditure
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more EE when you are trying to get warm, shivering and sweating to get cold.
Genetics
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340 genes implicated - prefer high fat sugary foods, greater number of fat cells, lower REE, decreased TEF, lower rates of fat oxidation etc.
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What is energy balance?
Merriam Webster - the relationship between the intake of food and the output of work - positive when the body stores energy and negative when the body draw on stored fat to provide energy for work.
First law of thermodynamics - energy cannot be created or destroyed - it is transferred from one to another.
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Basal Metabolic Rate - BMR - the energy requirement of all the cellular processes that are necessary to maintain life
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Resting Metabolic Rate - RMR - similar to BMR but with the additional EE associated with prior movement
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Hunger - physiological sensation that is triggered by the hypothalamus in response to cues about the stomach and intestinal distention, levels in blood and hormones.
Appetite - psychological desire to consume specific food, aroused by environmental cues.
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Stretch receptors in the stomach wall which increase or decrease the desire to eat via the hypothalamus
Blood nutrient levels can regulate body weight. The glucostatic theory - fall in blood glucose stimulate glucose sensitive neurones in brain to increase the drive for food whereas increased blood glucose may inhibit the neurones
Lipostatic theory suggests similar effects for blood glucose levels of lipids and the aminostatic theory is the same for amino acids.
Long term regulation - leptin circulates in blood in proportion of fat mass in the hypothalamus inhibits neuronal populations that increase or decrease EE.
Short term regulation - Cholecystokinin (CKK), peptide YY (PYY) secreted by small intestine in proportion to food digested
Maintaining weight loss - > third of lost weight re-gained it within 1 year, and most of the weight lost was regained within 3-5 years.
When over fat people lose weight adipocytes increase their levels of lipoprotein lipase which promotes fat storage
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Biochemical interaction should ensure energy balance. The reality is that psychological factors and presentation of energy dense foods can override those mechanisms and result in weight gain.