Energy Balance And Control Of Body Weight Flashcards
Body mass
Body=fat+fat free mass
How is body composition measured
Body density
Body water (measure of lean body mass)
Total body mass
Methyl histidine/creatinine excretion (proportion of muscle)
Skinfold measurements (biceps, triceps, supra iliac, sub scapular)
Mid arm circumference
Use of bio electrical impendance
Electrical signal is sent through the body
Travels quickly through lean tissue (higher % of water, good electrical conductor)
Travels slowly through fat (lower % of water, poor electrical conductor)
Device used info from this signal to work out body fat %
How is air displacement plethysmography used to work out body composition
Measure volume of chamber with and without subject
From subject weight and volume, can calculate body density, fat and fat free mass
Out of carbohydrates, fat, protein and alcohol, which is the most and least energy dense
Fat 9kcal/g
Alcohol 7kcal/g
Protein, Carbohydrate 4kcal/g
How is the energy from food used
Largest proportion of energy lost as heat (50%)
Less than 50% used for work
Energy used in metabolism = digestable - urine and sweat loss
What is the ideal energy requirement
Energy requirement = energy expenditure
Oxygen consumption proportional to energy expenditure
1l of O2 = 20 kJ
What does energy requirement depend on
Basal metabolic rate (kJ/hour/kg) Diet induced thermogenesis Physical activity Environmental temperature Growth, pregnancy, lactation Age
How is appetite controlled via the hypothalamic neurones
What 3 neurones are involved
What 4 long term signals are they stimulated by
Ghrelin
- from stomach
- stimulates NPY/AgRP => stimulate hunger
PYY3-36
- from intestines
- inhibit NPY/AgRP producing neurone, inhibit hunger
Leptin
- from adipose
- inhibit NPY/AgRP producing neurone, inhibit hunger
- stimulate POMC producing hormone, inhibit hunger
Insulin
- from pancreas
- inhibit NPY/AgRP producing neurone, inhibit hunger
- stimulate POMC producing neurones, inhibit hunger
Where do short term hunger and satiety signals come from
Via vagus and circulation
- GI tract
- Hepatic portal vein
- Liver
Causes of obesity, genetic
Very few cases of severe obesity due to leptin deficiency or MC receptor deficiency or other single gene defect
[leptin] usually higher in obese people, do not lose weight with leptin injections due to leptin resistance
Causes of obesity, energy expenditure and metabolic rate
The total metabolic rate, higher in obese
Causes of obesity, socio economic, cultural
Obesity in lower socio economic classes 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
Causes of obesity, endocrinological
Rarely due to adrenal hyperactivity,
hypothyroidism
T2D, result of obesity
Causes of obesity, physical activity
Children spend 65% less energy than 25 years ago
Food intake has not decreased proportionally
