Energy Metabolism Flashcards
How many additional calories per day will lead to obesity?
25
Similarly will wither away if have -25
What are the three different forms of energy that can be converted to heat?
- Chemical
- Mechanical
- Electrical
MEC.
First Law of Thermodynamics?
- Energy cannot be created or destroyed
- Can be transformed from one form to another.
Plants depend on energy captured from the sun to synthesise proteins, carbohydrates and fats (macros via photosynethesis).
Animals meet their energy needs from chemical energy stored in plants and other animals ie food.
Three things chemical energy from food is used for?
- Chemical work (synthesis of new macromolecules).
- Mechanical work (muscular contraction).
- Electrical work (maintenance of ionic gradients across membranes eg sodium-potassium pump (SPP).
SPP regulates fluid balance in cells. Cells = negatively charged on inside to outside which enables cells to do neg-pos charges.
Metabolic syndrome symptoms?
Present with three of five things:
1. Elevated blood pressure
2. High blood sugar
3. High tryicglicerides
4. Abdominal adiposity
5. Low HDL cholesterol.
Sub-optimal energy metabolism or fuel mismanagement.
Energy metabolism?
Balance between energy in, energy out and energy stored.
What is energy balance?
Energy balance =
energy intake +
energy stores) -
energy expenditure.
What happens if energy intake and expenditure are not equal?
- Negative energy balance = body uses energy stores ie glycogen, fat, protein.
- Positive energy balance = increase in body energy stores, primarily as fat.
How can energy consumed as food/drink be stored?
- Glycogen in the liver and muscles.
- Fat (accounting for the majority of energy storage) in adopocytes.
When energy is in short supply the body can source energy from where?
- Glycogen in the liver (100g) and muscles (400g).
- Fat
- Protein (a last resort in cases of starvation or malnutrition – amino acids are taken from skeletal muscle).
NB Liver glycogen keeps us going overnight.
Which fuel does the body burn first and why?
Glucose as it is the easiest to burn.
Body likes to keep stored fat for emergencies.
Second Law of Thermodynamics?
Second Law of Thermodynamics: All energy used by the body degenerates as heat.
Whenever energy is transferred or transformed (eg during cellular metabolic reactions) there is loss of energy in the form of heat.
When food is utilised in the body (chemical, mechanical or electrical work), this is always accompanied by loss of some energy in the form of
heat ie thermal energy that is no longer available for work inside the body).
What is the heat-generating potential of a food better know as?
Caloric value
Or kcal (1,000 cal = 1kcal)
What is a calorie?
Calorie = amount of heat to raise temperature
of 1g of water by 1°C.
In food we refer to 3k calories really. Ie 1 kcal.
Aussies use kilojoules.
Society focusssed on number of calories rather than the nutrient density.
Caloric value of each macronutrient?
Per 1g:
1. Carbohydrate, proteins: 4 kcal
2. Fat: 9 kcal
3. Alcohol: 7 kcal (very fast burning carb). Can’t be converted to glycogen. either used immediately or stored as glycogen. Body burns alcohol before food in a meal.
4. Fibre: 2 kcal (yielded from bacterial fermentation)
What is the energy currency that all life relies on?
ATP (adenosine triphosphate)
Used to fuel all cell processes.
How is ATP produced?
Conversion of acetyl Co-A via the Krebs Cycle and the Electron Transport Chain.
Which organelle in body doesn’t have mitrochondria?
Red blood cells
Co-factors needed for Krebs cycle?
- Magnesium
- Manganese
- CoQ10
- Copper
- Vitamin B1, B2, B3, B5
- Alpha Lipoic acid
- Fe
- Sulphur
What can damage mitochondria?
- Nutrient deficiencies
- Toxins (inc poor liver detoxification and elimination pathways)
- Heavy metals (eg Mercury, Arsenic & Aluminium - oxidise very easily) can damage mitochondria and interfere with energy production
EIGHT factors that influence how much energy a person has? Clue, nutrition is only one factor!
- Good nutrition: sufficient intake (fuel). Crucial for cell respiration (Krebs cycle).
- Digestion & absorption: crucial for liberation of nutrients from food. Good GI health vital for nutrient absorption.
- Respiratory (iie lung) health: Oxygen intake. Consider lung diseases, smoking, chronic hyperventilation.
- Heart & circulation health. Key in nutrient (‘fuel’) delivery to cells.
- Antioxidants to protect against mitochondrial damage, as well as minimal toxic load.
- Thyroid health: upregulates metabolism.
- Adrenal health Adr and NorAdr increase energy delivery ie get us up in morning (stimulate glycolysis, increase HR and BP, dilating airways).
- Healthy detoxification: to prevent mitochondrial damage, optimise liver detoxification and routes of elimination (bowel, kidneys, skin, lungs) and minimise toxic exposure. If liver busy detoxing won’t be creating energy.
- Sleep hygiene: promote melatonin production (a potent antioxidant).
- Stress:: having a goal; acts of kindness; being in love – all these things can create energy.
Grief, a lack of sense of purpose and unresolved problems can reduce one’s energy
In terms of nutrition what can affect energy production?
- Glycemic load - refined v. unrefined
- Micronutrient content - how much how quality?
- Fats: n-3, EVOO or damaged fats?
- Fresh fruit and veg v. boxed foods
- Hydration
What three factors does energy expenditure depend on? NB not food!
- Basal Metabolic Rate (BMR) - 65-75% energy depends on this. Includes everything non-physical, body temp, CV system, CNS, ANS, breathing. Keeping the lights on.
- Physical Activity (20%) - excercise but also NEAT (non-exercise activity thermogenesis) eg walking around the house, typing, brushing teeth, restless legs, fidgeting.
- Thermic Effect of Food (10%) different foods require different energy requirements to digest
What is Basal Metabolic Rate (BMR)
Minimum level of energy required to sustain life ie energy used to maintain basic physiological functions such as cardiac contractions, ventilation and cell growth.
How much does BMR account for as pc of energy expenditure?
BMR accounts for 60-75% of total energy expenditure, mostly from the metabolic activity of lean tissue (i.e. non-adipose tissue) collectively referred to as fat-free mass (FFM).
What FIVE factors can impact BMR?
- BMR varies between individuals, mostly due to muscle mass. BMR will increase with more lean muscle.
- Physical activity can also impact BMR: exercise can elevate metabolic rate for up to 48 hours and can also increase fat free mass (FFM) which further elevates BMR.
- Other factors that can affect BMR include stress, caffeine, nicotine, medications, fever, injury,etc.
- Genetics
- Thyroid hormones (endocrine organ) - command centre for energy metabolism. Literally responsible for turning up the heat. All body cells have thryroid receptors.
What is thyroid gland responsible for?
Regulating energy metabolism
By secreting hormones that control metabolic rate of cells.
Where is TSH produced?
Anterior pituitary gland
What hormones does TSH trigger release of?
- Thyroxine (T4)
- Triiodothyronine (T3)
From thyroid gland.
T4 = primary thyroid hormone; less potent than T3.
Co-factors for T3 and T4 production?
ITSZI
- Iodine
- tyrosine
- Zinc
- Selenium
- Iron
Where is T4 converted to T3?
Liver and kidneys.
Sub-clinical thyroidism symptoms?
Found in 8-10% of the population (60% are unaware) – more common in women.
- Can present as low energy
- Reduced appetite
- Weight gain
- Feeling cold
- Dry skin
- Thinning hair
- Constipation
- Irregular periods
- Depression
- Goitre
What nutrient deficiences cause sub-clinical hypothyroidism?
- Iodine
- Selenium
- Zinc
- vitamin D
What non-nutrient factors contribute to sub-clinical hypothyroidism?
- Autoimmunity,
- Fluoride / chlorine (halogens) displace iodine
- Mercury (amalgams, tuna) so displaces iodine and therefore disables T4.
- Exposure to endocrine disruptors such as BPA.
- Gluten
NB Often an AI issue ie Hashimotos - antiobidies can be tested on a full thyroid panel. If elevated know they are being attacked. Big connection between gluten and hypothyroidism. Antiobidies remain for six months.
Why is a full thyroid panel beneficial?
We need to know root cause why the thyroid isn’t performing ie:
1. Iodine deficiency? Seaweed… govt fortification eg livestock feed so it hits us indirectly.
2. Selenium deficiency? (Brazil or South America only) deficiency? Depleted soils.
GPs do same test with same action ie thyroxin… blunt instrument
3. AI?
Full panel = TSH, T4, T3 and thyroid antibodies. Docs only do TSH.
What kinds of diseases and traumas can affect energy metabolism upwards or downwards?
- Infection and fever (thermogenesis in action!) raises one’s metabolic rate. Trying to make body inhospitable. Starve a fever and feed a cold… body’s metabolic rate increases. Need to provide more energy.
- Surgery: Increase requirements to aid recovery (amino acids, vit C to make collagen) or an injury.
- BMR of patient with severe burns can more than double during recovery. Immune system and tissue repair.
- Anorexia Nervosa patients need energy intake up to 2.5 times their BMR during re-feeding.
- Cancer patients energy requirements may reach 145% of BMR.
What is the thermic effect of food?
Amount of energy required to digest and process the food you eat (done in lab). Also referred to as thermogenesis.
TEF accounts for approx. 10% of the total daily energy expenditure in an average diet.
What are the thermic rates for macros?
Different foods have different thermic dffects (TEF):
Fats = 0-3%
Carbohydrates = 5-10%
Proteins = 20-30%
While proteins take more energy to digest and be absorbed, fats barely take any. Proteins better for weight loss programmes.
Wholefoods have a higher thermic TEF (thermic effect of food) than processed foods.
Caloric guidelines for men and women?
Women: 2000kcal/day
Men: 2500kcal/day for men.
What do govt caloric guidelines ignore?
- Body size
- Muscle mass
- Current state of metabolic health
- Sedentary v. active lifestyle.
What is DNL?
de novo lipogenesis (DNL) = metabolic pathway that synthesises fatty acids from excess carbohydrates ie new fat generation
What happens metabolically when we eat each macro?
-
Carbs:
a) Immediate energy conversion under normal conditions (preferential).
b) Excessive carbs, especially when refined (combined with a sedentary lifestyle), will force metabolism into DNL - a key driver of ‘Metabolic Syndrome’. - Fructose = carb exception. Unlike glucose, which can be metabolized by most cells in the body, fructose is mainly metabolized in the liver. Liver easily converts fructose into fatty acids. High amounts of fructose result in high levels of de novo lipogenesis.
- Fats in excess stored in adipose tissue under normal metabolic conditions.
Think: we burn the easy stuff and store the precious stuff.
When you consume fructose, it’s absorbed in the small intestine and transported to the liver. Enters the glycolytic pathway, where they can be further metabolized for energy production or converted into fat. Excess fructose consumption can lead to adverse metabolic effects, including increased fat synthesis and insulin resistance.
What happens metabolically if undereat?
Negative energy balance forces body to use stored fat for energy - weight loss.
Chronic calorie restriction may lead to:
- slowing down of metabolism
- micronutrient deficiencies.
Can make it more difficult to continue losing weight. Thyroid kicks in. Slows us down. Won’t fidget ie NEAT activities, will get colder.
Nutrient dense food necc to help re-establish healthy metabolism for weight loss to continue.
Biology always wins. 5/6 people who calorie restrict will put weight back on. Survival instinct… body wants us to get back to previous levels.