Energy metabolism and weight loss Flashcards
What are the first and second laws of thermodynamics
First law of thermodynamics: energy cannot be created or destroyed, but can be transformed from one form into another
Second law of thermodynamics: all energy used by the body degenerates as heat (whenever energy is transferred there is a loss of energy in the form of heat)
How do plants and animals capture their energy
plants from the sun to synthesise proteins, carbs and fats
Animals from chemical energy stored in plants and other animals
The chemical energy obtained from food is used to perform three main functions
Chemical work - synthesis of new macoromolecules
Mechanical work - muscular contraction
Electrical work - maintenance of ionci gradients across membranes
Energy consumed in the form of food and drink is stored as what in the body
Glycogen in the liver and muscles
Fat - majority of energy storage
When energy is in short supply, where can the body source energy from
Glycogen in the liver and muscles
Fat
Protein (last resort in case of starvation)
What are calories
the heat-generating potential of food
How many calories (kcal) are in 1 g of macronutrients
Carbohydrates
Protein
Fat
Alcohol
Fibre
Carbohydrates - 4
Protein - 4
Fat - 9
Alcohol - 7
Fibre - 2
What key nutrients are needed for ATP synthesis / cellular respiration
Mg, Mn, Fe, Su, CoQ10, Cu, B1,2,3,5 and alpha lipoic acid
What factors might impair ATP production resulting in deficiency (eg fatigue)
Sufficient nutrient intake - co factors
Digestion and absorption - liberation and absorption
Respiratory health - O2 (eg lung disease/smoking)
Heart and circulation (delivery of nutrients)
Mitochondrial health - needs antioxidants and minimal toxic load
Thyroid health - upregulates metabolism
Adrenal health - adr and NorAdr increase energy delivery
Healthy detoxification - prevent mitochondrial damage
Sleep hygiene - melatonin as antioxidant
What three variables does a persons daily total energy expenditure depend on
- Basal Metabolic Rate (BMR)
the minimum level of energy required to sustain life
Accounts for 60-75% of total energy expenditure, mostly from metabolic activity of lean tissue AKA fat free mass FFM - Physical activity
Impacts BMR as raises metabolic rate for up to 48 hours, increases the FFM - Thermic effect of food (TEF) / thermogenesis
The amount of energy required to digest and processed food eaten
What additional factors might effect the basal metabolic rate
caffeine, stress, smoking, meds, fever, genetics, thyroid
What role does the thyroid play in regulating energy metabolism and name the hormones and glands involved in the process.
the thyroid secretes hormones that control the metabolic rate of cells.
TSH produced by anterior pituitary gland, triggers release of thyroxine T4 and triiodothyronine T3 from thyroid gland
Which is more potent - T4 or T3 - and what nutrients are required to support the production of T4 and T3
T3 is more potent.
Iodine, tyrosine, Zn, Se, Fe are needed for T4 and T3 production
What percentage of the population have subclinical hypothyroidism and how is it categorised
8-10% of the population have hypothyroidism
It is categorised as TSH above range but normal levels of T4 and T3
What are the signs of hypothyroidism
low energy, reduced appetite, weight gain, feeling cold, dry skin, thinning hair, constipation, irregular periods, depression
What nutrient deficiencies may be indicated in hypothyroidism
iodine, selenium zinc Vit D
Exposure to BPA
What % of total daily energy expenditure is spent on thermogenesis (energy to digest and process food), and what is the Thermic Effect of:
Fats
Carbs
Proteins
10%
Fats: 0-3%
Carbs: 5-10%
Proteins: 20-30%
Therefore leveraging the thermic effects of proteins can be helpful to weight loss.
What is de novo lipogenesis (DNL) and what disease state is it a key driver of
the metabolic pathway that synthesises fatty acids from excess carbohydrates
DNL is.a key driver of metabolic syndrome.
Over eating - what happens when excess calories are consumed, specifically what happens with excess CHO, Fructose and Fats
Carbohydrates (CHOs) are preferentially used for immediate energy. Excess results in DNL
Fructose - liver converts it into faty acids. High fructose = high levels of DNL
Fats - excess stored in adiposst tissue
What is the consequence of excessive CHO consumption
especially when they’re refined, they force metabolism into DNL (de novo lipogenesis… synthesis of fatty acids from carbs)
Under-eating - what can chronic calorie restriction lead to
whilst it can force teh body to use stored fat for energy, chronic restriction can slow down metabolism and make it difficult to continue losing weight.
Eat more food but right type to re-establish healthy metabolism
What is nutrigenomic testing
provides personalised macronutrient profiles based on genes and how well you metabolise fats and carbs
Ketosis - when glucose is insufficient to maintain glycogen stores in the liver and muscles, the brain experiences this as stress - what does this result in (what hormones are increased and decreased) and what does this lead to the release of
increase of cortisol and sharp drop in insulin production
Leads to release of excess supply of fatty acids from adipose tissue, leading to a partially incomplete metabolism in which ketones are produced which the brain can use as fuel
What are the key mechanisms that control satiety
Presence of food in stomach - Gastrointestinal distention
Presence of food in duodenum - CCK released from duodenum
Liver signals presence of nutrients to the brain via the vagus nerve