Energy, Starvation and Obesity Flashcards
(40 cards)
What is the Body Mass Index (BMI)?
BMI = weight in kg / (height in m)2
It is a measure of persons weight relative to their height
The BMI categories are:
- Underweight = <18.5
- Normal = 18.5 - 25
- Overweight = 25 - 30
- Obese = 30-40
- Morbidly Obese = 40+
BMI is an imperfect predictor of ideal weight:
- For age >35; BMI =27 adds little extra risk that a BMI = 20
- Mesomorphic athletes have high BMI without any inherent risk
Contrast the different fat profiles of males and female at the onset of puberty
At puberty, females gain fat while males lose fat.
Females gain fat to make them suitable for child rearing -> women with low fat often lose their menstrual cycle (amenorrhea)
How should the BMI be applied to children?
Although BMI = 25 is healthy in adults, this is obese for children.
When applying the BMI to children you must apply the BMI to a standardised curve due to the changing body proportions experienced in childhood.
How can body fat be measured?
- Caliper measurements of skinfold thickness
- Body density measurements by immersion in water (hydrodensity)
- Bioelectrical impedence (fat people are better insulators
What waist circumference sizes are associated with increased risk of metabolic complications?
Sex - increased risk - substantially increased risk
Male > 94cm / >102cm
Female >80 cm / >88cm
Explain the concept of protein sparing
Protein will be used structurally when enough energy is provided by carbohydrate and fat - allowing protein to be preferentially used structurally and not for gluconeogenesis
There are no storage proteins and a healthy body
The human body contains 12 kg of protein. It can
readily lose about 400g from muscle mass, but continued losses cause stress.
What happens to the gut lining during long term starvation?
Long term starvation leads to progressive intestinal villi atrophy
There is nothing to absorb during starvation so the gut cannibalises itself -> providing 60g of protein to use for energy production/day
The sloughing of the intestine complicates refeeding because the gut has poor resorbtive capacity. Milk is often used for refeeding because it has equal portions in energy of protein, carbohydrate and fat.
Lactase may need to given supplementary
Elicit the differences between Kwashikor and Marasmus conditions
Both conditions arise from protein-energy malnutrition states.
Kwashikor
- Moderate energy deficiency
- Severe protein deficit
- Oedema with some subcutaneous tissue
- These children have enlarged fatty
liver, low serum albumin and oedema (fluid
accumulation = pot belly - Aflatoxin, derived from aspergillus fungus on corn, contributes to the severity of
kwashiorkor by the formation of aflatoxin epoxides -> reacts with guanin in DNA -> cell death/cancer
Marasmus
- Severe energy deficit
- Severe protein deficit
- ‘skin and bones’ appearance with little or no subcutaneous tissue
Discuss the epidemiology of lactose intolerance
In humans, in non-dairy consuming societies, lactase production usually drops about 90% during the first four years of life.
Populations that have adapted to drink milk as adults have a range of mutations on chromosome 2 which reduce the shutdown in lactase production.
In reference to nitrogen balance, what factors may alter this nitrogen use
Positive Balance = nitrogen in > nitrogen out
- During growth more nitrogen is consumed than excreted to build proteins
Neutral Balance = nitrogen in = nitrogen out
- General basal state
Negative Balance = nitrogen in < nitrogen out
- More is excreted than consumed
- Occurs in starvation, burns victims, post-operative patients and AIDS patients
What is cachexia?
Cachexia is an extreme example of loss of muscular and adipose tissue in terminal illness (often cancer).
It is caused in part by high levels of TNF-alpha that mediate a negative nitrogen balance due tot he breakdown of tissues
What is bulimia nervosa?
** Bulimia nervosa** is a serious psychiatric illness
characterised by recurrent binge-eating followed by purging or overexercising
Behaviours include self-induced vomiting, fasting, overexercising and/or the misuse of laxatives, enemas or diuretics
health professionals incorrectly assume that a person must be underweight and thin if they have an eating disorder - they actually maintain a normalish body weight. A dentist is often the professional who picks up the problem -> acid of vomit rots the teeth.
What is annorexia nervosa
Annorexia is an eating disorder characterized by immoderate food restriction, inappropriate eating habits and a distorted body self-perception.
There is a prevalence rate of 1-2% among schoolgirls and university students (males have one tenth of this rate). Higher rate in higher social classes.
Tend to be precipitated by:
- Stressful life events
- Genetics
- Turbulent family relationships
As a result of annorexia, menses may cease, the patient may develop low blood pressure, slow heart rate, and become very sensitive to the cold.
Discuss the positives and benefits of a vegetarian lifestyle
Lacto-Ovo vegetarians
Eat milk and eggs and generally do not exhibit
deficiency syndromes. Women may become Iron deficient and anaemic (recall that plants do not have blood).
Vegans
Eat no animal products. Vegans risk deficiencies in Vitamin B12 (peripheral neuritis and pernicious anaemia), Vitamin D, riboflavin, Iron, Calcium
and Zinc.
Positives of vegetarian lifestyles
- lower bodyweight, diabetes, blood pressure, arteriosclerosis, constipation and cancer
Negative of vegetarian lifestyles
- children filling up before eating
enough protein for growth, women providing inadequately for foetal development and breast milk and women developing irregular menstruation
Given the malnourishment in the world, do we need to be producing more food for the earth’s population?
No
One in seven people in the world are malnourished but the solution isn’t more food production but getting food to the right places
30-50% of the 4 billion metric tonnes of food produced globally each year becomes waste
Americans waste 40% of their food
How much energy is required to be uptaken by the human adults?
For human adults the need for energy is
around 10MJ per day.
Less than this and we risk starvation, wasting and high rates of infection.
More than this and we risk obesity and a different set of disease conditions
What does bomb calorimetry measure?
Bomb calorimetry gives a direct measure of the energy of combustion in food
It uses electrical ignition to produce the reaction:
Food + O2 -> H2O + CO2 + NxOx + heat
The relative heat efficiencies / Atwater factors of common compounds:
Discuss the energy content of alcohol and its usefulness as a fuel
Alcohol is an energy dense fuel -> 30 kJ of energy per gram of alcohol
Humans and cars carry out the same chemistry (by different means obviously) to get the exact same amount of energy from alcohol compounds:
alcohol + O2 -> CO2 + H20
Alcohol is converted to acetate in the human body. This acetate is capable of taking either of two pathways:
- Burn it -> produce energy
- Store it when have sufficient energy -> fat deposition
What components of energy expenditure contribute to the 10 MJ energy requirement of the human diet?
- Physical Activity = 20-40%
- Temperature regulation / other = 2-4%
- Specific Dynamic Effect (SDE) = 8-10%
- Basal Metabolic Rate = 60%
What is Specific Dynamic Effects (SDE)?
SDE is the energy expended in the absorption and transport of nutrient, digestive enzyme synthesis, gut mobility and gut replacement.
it is the energy involved in obtaining nutrients from food
8-10% of daily energy turnover
Also known as postprandial thermogenesis or heat increment of feeding
What is the basal metabolic rate (BMR)?
BMR is the energy to pump blood, sustain cellular processes and the minimal metabolic activity to maintain 37 degrees.
It is the largest component of normal activity
It is measured strictly in subjects:
- at rest
- 12 hours after last meal
- in a thermoneutral environment of 25-30 degrees
Is exercise an efficient consumer of daily energy?
Exercise is generally NOT a great a consumer of daily energy.
As a multiple of BMR sitting approximates to 1.2, Walking 3.2 and vigorous digging =6. Vigorous exercise is rarely sustained
Compared to the daily metabolic rate, exercise has relatively little effect on daily energy turnover
However, exercise is critical to health and weight regulation. Regular moderate exercise
of only 30 minutes a day protects against a range of diseases
What benefits does exercise confer to the health of people?
Exercise improves:
- Health
- Cardiovascular fitness
- Cancer protection
- Bone strength
- Muscle strength
- Lung capacity
- Weight control
While also improving the immune system, nervous system, endocrine system and protection against cancers.
How does BMR confer with body shape?
The BMR of humans and other mammals is dependent on body size and shape as a determinant of thermal efficiency
Surface area / Volume ratio is a determinant of BMR -> higher ratio is proportional to higher BMR
Compact bodies are more efficient – tall and skinny has a higher BMR and utilise more energy.
Large, sphereoid bodies shapes display greater conservation of energy due to less surface area.
