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
What is the role of the hypothalamus in appetite regulation
Arcuate nucleus in the hypothalamus - neruons that stimulate or inhibit food intake.
Gut hormones modulate digestion and absorption of nutrients and reach the hypothalamus via the vagus nerve
List 2 hormones/neurotransmitters that act to increase appetite
Neuropeptide Y (NPY)
Ghrelin
List hormones/neurotransmitters that promote satiety
Cholecystokinin (CCK)
Insulin
Glucaogon
Glucagon-like peptide 1 (GLP-1)
Bombesin (found in brain and GI tract)
Leptin
Cholecystokinin (CCK) - where is it secreted from, what promotes its secretion, and what are its key function
Released from the duodenum
Protein and fat stimulate its production
- stimulates gall bladder to release bile
- stimulates pancreas to release pancreatic juice
- delays gastric emptying
- acts on CCK receptors in CNS and in satiety centres in the brain stem
Insulin - what stimulates its release and where is it released from and what is its key function
released by beta cells of teh pancreas in response to elevated blood glucose.
Key function to lower blood glucose bu facilitating its storage in muscle tissue and the liver as glycogen
What role does insulin play in fat storage
Fat cannot be stored without insulin.
Insulin controls the storage and release of fatty acids in and out of adipose tissue via:
- regulation of several lipase enzymes
- activation of GLUT-4 (glucose transport protein-4) which transports glucose into fat cells
What are the metabolic actions of insulin
- Stimulate synthesis of triglycerides from free fatty acids
- inhibits release of free fatty acids from triglycerides
- increases synthesis of liver glycogen - thereby increasing glucose uptake and storage
- inhibits gluconeogenesis
- stimulates glucose uptake in skeletal muscle
Reduces hunger via hypothalamus
What can be a cause of insulin resistance
chronic excess energy intake (and sedentary lifestyle) leads to body producing excessive amounts of insulin.
What impact does insulin resistance have on metabolic function
- inhibits lipolysis (breakdown of fat from adipose tissue)
- This leads to visceral fat deposition/central adiposity
- As visceral fat increases, ADIPONECTIN production decreases
What is adiponectin and its role
an adipose-specific protein hormone that increases the oxidation of fatty acids, promotes the clearance of excess fat in tissues and improves insulin sensitivity - the higher it is the less inflamation
Adipose tissue acts as an endocrine organ - explain
it is capable of producing hormones and inflammatory cytokines such as TNF-a and interleukin-6. Raising systemic inflammation. Leading to further hormone resistance, obesity and chronic disease.
How does visceral fat and FFAs impact the liver - what is the process
Visceral fat supplies a constant source of excess free fatty acids (FFAs) because lipolysis isn’t working properly - additional FFAs pass into the blood and LIVER.
What signals does insulin normally send to the liver and what impact does insulin resistance have on this
Stop making glucose - inhibit gluconeogenesis
Store available blood glucose as glycogen - glycogenesis
In insulin resistance both these processes respond poorly to the insulin signal - potentially leading to elevated glucose levels.
How is fructose metabolised and what diseases is it linked to
when glycogen stores are full fructose is converted directly to liver fat.
Excess fructose intake is associated with NAFLD, obesity, hypertension, , excess uric acid (gout), accelerated ageing, diabetes complications
What is the role of ghrelin and where and when is it produced.
produced by stomach cells when it’s empty to stimulate hunger. Suppressed after a meal
What can impact the production of ghrelin (increase and decrease)
dysregulated sleep and elevated cortisol increase ghrelin section
Exercise decreases
What combination of macronutrients can support ghrelin production
high protein (35% of calories) with moderate carbs (45%)
What is leptin and what is its role
leptin is an adipokine produce by white adipose cells in proportion to adiposity (overall body fat)
Increased adiposity = increased leptin = suppressed appetite.
If the role of leptin is to suppress appetite, and it’s produced by adipose cells meaning that levels are therefore raised in obese people, why does it not stop them from eating?!
Obesity promotes a number of inflammatory cellular processes that weaken leptin signalling - leading to leptin resistance.
What functions of the hypothalmic-pituitary axis does leptin effect and with what end result
modifies insulin sensitivity, tissue metabolism, stress responses, reproductive function.
Ultimately the changes in metabolism produce abdominal weight gain, thigh and hip weight gain in women, chronic fatigue, sleep problems, CV distress etc
Viscious cycle!
How can we increase leptin sensitivity - list 6 ways
Go gluten free - wheat gluten can stop leptin binding to leptin receptor
Reduce sugar consumption - especially fructose which induces leptin resistance
support gut flora with prebiotics which can improve sensitivity
Reduce inflammation - anti inflamm diet to restore sensitivity
Regular exercise - increase sensitivity
Sleep hygiene - improve sensitivity
Gut flora and obesity - what gut flora my be implicated in obesity
A higher ratio of FIRMICUTES v BACTEROIDETES PHYLA
What type of bacteria does a high fat diet cause an increase and reducition of
Increases gram negative bacteria
Reduces bifidobacteria
What role to SCFAs play in obesity
SCFAs liberated by the gut flora have been shown to INCREASE SECRETION OF APPETITE CURBING NEUROPEPTIDES AND GUT PEPTIDES which support integrity of intestinal lining.
What is metabolic endotoxemia
risk factor for obesity - it’s a low grade inflammatory response due to circulating endotoxins (LPS)
SCFAs increase secretion of gut peptides which support the integrity of the intestinal lining. Intestinal permeability is associated with metabolic endotoxemia which causes what
enhanced LPS absorption (LPS are a component of the the outer membranes of gram negative bacteria.)
low grade chronic inflammation
insulin resistance
How can the use of prebiotics aid in weight management
promote satiety
reduce hunger
reduce food ingestion
suppress ghrelin
increase peptide YY and GLP-1
What are prebiotics
non digestible carbs that promote the growth of beneficial gut bacteria
How have probiotics been shown to support weight management
trials have show probiotics with in combination with diet can lower blood glucose levels and improve insulin sensitivity
What role has dopamine been seen to have in obesity
obese people have been shown to have reduced numbers of dopamine receptors in their brains and get less of a reward response from foods. Increase risk of over eating
Name factors affecting food intake
cultural - eg religious traditions
sensory - appearance/smell/advertising
emotional - comfort eating
Hormonal/disease state, climate, meds
Why do sharp blood sugar spikes lead to cravings?
The drops in blood sugar increase activity in the nucleus accumbens - the area of the brain that produces the desire to eat.
How can we maintain stable blood sugar
protein with every meal
avoid refined sugar and carbs and include complex carbs, low GI GL food (beans, wholegrain, veg)
Choose organic foods
Eat mindfully
Strategies to regulate food intake - name 4
regulate blood sugar levels
Keep track of food - food diaries/monitor weight
mindful eating - listen to your body, use your senses, be still, sit, no electronics
Focus on adding rather than taking away - nutrient dense
List practical methods to support weight loss
reduce stress - herbs/Epsom bath/balance blood sugar/diaphragmatic breathing
good sleep hygiene - avoid coffee/alcohol/blue lights/no eat or exercise 3 hours before bed/routine
alternate day fasting
time restricted feeding eg 16:8
Low carb/high fat diet (eg ketogenic) - lack of glucose induces teh body to burn ketones and fat for energy
HIT - creates O2 debt which is repaid via EPOC - excess post exercise oxygen consumption. Increases metabolic rate 36 hours post exercise
What herbs could support stress and therefore aid weight loss
adaptogenic and nervine (relaxing) herbs - ashwagandha, chamomile, passionflower
When creating a nutritional plan, what factors should be evaluated
- does the plan address behavioural triggers or eating
- does the plan provide all necessary macronutrients and micro molecules
- is it a diet or lifestyle change
- what is the motivation
- does the plan offer education and support
- does the plan include exercise
