Energy Balance Flashcards
How Is Body Composition Measured?
Body = Fat + fat free mass
- Body density (More fat=more dense)
- Body water
- Total body K (potassium)
- Methyl histidine or creatinine excretion
Skinfold measurements - Biceps, triceps, supra iliac, sub scapular
- can get rough estimate of percentage of body fat
- Mid-arm circumference
- leg may hhave edema so arm used
How is body composition measured with Bioelectrical Impedance?
- electrical signal is sent through the body
- travels quickly through lean tissue (high % water, therefore good conductor of electricity
- more slowly through fat lower % water , poor conductor of electricity.
Bioelectrical Impedance devices use the information from this signal to work out body fat percentage.
How is body compostition measured with The bod pod?
**Air Displacement Plethysmography **
* Measure volume of chamber with and without subject
* From subject wieght and volume can calculate body density and fat and fat free mass
How do we get energy from food?
Total energy : Heat of combustion
Digestible energy : Absorbed
Metabolisable: Digestible minus energy that lost in urine sweat and skin
50% lost as heat. Less than 50% used for ‘work’
What are our energy requirements?
**Energy requirement = energy expenditure **
Oxygen consumption proportional to Energy expenditure
1 litre oxygen : 20 kjoules
What does the Energy requirements depend on?
-
Basal metabolic rate
- kj/hour/kg body weight
- when doing nothing -
Diet induced thermogenesis
- when eat, heat relased in metabolism
- different for everyone -
Physical Activity
sitting = 1.7BMR
football = 7BMR -
Environmental temperature
- eat less
- but dont include this when calculating -
Growth, pregnancy, lactation
-0.8 MJ or 200 kcal/day in trimester 3
-2 MJ or 500 kcal /day in lactation
infant year one, requirement 2x adult /kg bw -
Age
decrease in BMR and activity
How does Intake v Expenditure of energy have significance?
If balanced = maintain weight
Most people maintain relatively constant body weight.
Regulation of Energy Intake
Hypothalamus
1. hunger centre
2. satiety centre
Regulation of Energy Intake with satiety (full)?
Long term signals: SATIETY
Leptin and insulin - Reducing apatite
- leptin signals the state of the fat stores
- plasma concentration reflects size of fat stores
- insulin signals the fullness of carbohydrate stores
- act in the hypothalamus through variety of neurotransmitters and neuropeptides.Both
* Inhibit hunger pathways
stimulate satiety pathways*
Regulation of Energy Intake with Hunger?
leptin and insulin low
- signal need for energy
BOTH
hunger pathways stimulated
satiety pathways suppressed
Neuropeptide Y (NPY) is hunger signal
Ghrelin (stomach and hypothalamus) hunger signal - it means gut is empty and u need to eat
Pro-opiomelanocortin (POMC) related peptides, PYY 3-36 suppresses appetite
Regulation of Energy Intake with Hunger and satiety?
Integration of hunger and satiety signals by the hypothalamus
Signaling molecules are released by:
* stomach, intestine, adipocytes, pancreas.
* signals integrated in the arcuate nucleus of the brain generating the feeling of hunger or satiety
Appetite control via hypothalamic neurons?
- Stomach empty - ghrelin produced
- ghrelin strimulates NPY/AgRP producing neurons
- And NPY and AgRP stimulate hunger
- PYY3-36 (from intestine) inhibits NPY/AgRP producing neurons
- Inhibits feeling of hunger
- Leptin and insulin produced
- stimulates pomc neurons
- inhinit hunger and give stimulate feeling of satiaty
Where do short term signals come from?
- the GI tract
- the hepatic portal vein
- the liver
They bring about the feeling of satiety through vagus nerve and circulation
long term - better
short term - bad
Trend of obesity?
- about two-thirds (66 per cent) of adults are now overweight or obese.
- obesity has tripled in the past 20 years and is still rising.
Causes for obesity?
- Genetic
- Socio-economic, cultural
- Endocrinological
- Physical activity
Genetic causes for obesity
Rare
1. leptin
very few cases of severe obesity due to leptin deficiency or MC receptor deficiency or other single gene defect (and they act through increased appetite)
Leptin concentrations usually higher in obese people and they do not lose weight with leptin injections
Usually Leptin is proportial but obese people develop Leptin resistance
Metabolic Rate in obese people
Basal Metabolic Rate is usually higher in obese as you are increasing both body fat mass as well as lean muscle mass
What is the socio-economic, cultural cause of obesity?
- obesity higher in lower socio-economic class in the UK and the Western world
- in affluent classes in poorer areas of the world - lifestyle and eating habits and different perception of desirable size and status
What is the Endocrinological cause of obesity?
- rarely
- adrenal hyperactivity (hypothroritism)
- hypothyroidism
- type 2 diabetes is a result of, not a cause of obesity
How is Physical activity a cause of obesity?
Physical activity
- children spend** 65% less energy **than 25 years ago.
- food intake has not decreased proportionally
Link between Microbota and obesity?
Evidence that GI tract of lean subjects has more diverse microbiota than obese
Faecal transplants from obese to lean have resulted in obesity and vice versa (e.g sterile gut from antibiotic treatment)
- Some gut microbes digest components of fibre
- Produce butyrate , colonic cell proliferation and maintenance of healthy gut barrier
- Produce propionate, stimulates PYY production by colonic cells and decrease appetite
FTO gene link to obesity?
FTO gene codes for 2 oxoglutarate dependent dioxygenase
Subjects with 1 copy of the FTO gene - 1.5 kg heavier
2 copies of the genes - 3 kg heavier
NIH
People with “high-risk” FTO genotypes exhibit preference for high-fat foods, reduced satiety responsiveness, andgreater food intake consistent with impaired satiety.
Risk factors for obesity?
- low level of education
- chronic disease
- little physical activity
- heavy alcohol consumption
- getting married
- giving up smoking
Conditions caused by or associated with obesity?
Cardiovascular disease
* relative risk MI x1.9 as likely tp develop with obesity
- angina x2.5
- stroke x3.1
- venous thrombosis x1.5
- Diabetes mellitus type 2 . Insulin resistance (2.9)
- Hypertension (2.9)
- respiratory problems
- gall bladder stones (2)
- osteoarthritis in weight bearing joints (11.8)
- reduced fertility in men (decreased androgens)
- polycystic ovary syndrome
- breast, endometrial, colon & prostate cancers
