Nutrition BS911

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NutritionBS911

• Body composition, weight regulation and the
  female athlete triad
• Week 7

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Why assess body composition?

• Body mass does not provide an indication of
  composition and distribution
• Overweight and over fat are not synonymous
• Height/weight ratios have obvious problems e.g.
  derived on reference man

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Why Are We Obsessed With Body Composition?

• For reasons of health, aesthetics and performance
• Heavily influenced by societal aspects
• Monitor childrens growth and identify early link
  to CHD risk factors
• Weight categories and making weight
• Often leads to severe dehydration and
  deterioration in performance
• Athletes often use acute weight loss techniques

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Composition of the Human Body

• Two Compartment Model

• Four Compartment Model

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The Relationship Between Lean Body Mass, Fat Free
Mass and Minimal Body Mass
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What Is Normal Body Fat?

• Men Women
• At risk ?5 ?8
• Below Average 6-14 9-22
• Average 15 23
• Above average 16-24 24-31
• At risk ?25 ?32
• Lohman, 1992

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Assessing Body Composition

• The human body may be analysed in many ways the
  best way will depend on the end sought and the
  practical measurement Keys and Brozek 1953
• Difficult to measure composition in vivo
• Two methods are direct (chemical analysis) and
  indirect (skinfolds etc.)
• Most of the following methods have been validated
  using cadavers

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Height - Weight Tables

• Consulting room instrument.
• Actuarial data re insurance risk.
• Overweight over-fat? or over muscled?
• 17 of 25 All-American football players rejected
  for military service
• Body density, not height-related mass, is the
  best measure of fatness (Welham and Behnke,
  1942).

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Body Mass Index (BMI)

• BMI Body mass (Kg) / Stature2 (m)
• Higher correlation with body fat than height
  weight tables.
• Correlates with relative risk of all cause
  mortality.
• Desirable BMI range
• 21.3 to 22.1 kg.m-2 for women.
• 21.9 to 22.4 kg.m-2 for men.
• Overweight is 25-29.9
• Obese is gt30
• Underweight lt 18.5.

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Hydrostatic Weighing (HSW)

• Gold standard developed by Behnke and Pace in
  the 1940s
• Determine the density of fat and muscle
• Density MASS / VOLUME
• Archimedes principle of water displacement
• Weight in air - weight in water mass of water
  displaced.

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Hydrostatic Weighing cont...

• Density of water is 1g.cm-3
• Density of muscle is greater than water 1.1g.cm-3
• Density of fat is lower than water 0.91g.cm-3
• Therefore fatter people float weigh less
  underwater larger volume smaller density
• Lean people sink more!

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Sources of Error in HSW

• Residual lung volume
• Intestinal gas
• Water density/ water temperature
• Individual variability in density of lean tissue
• Variation in bone mineral density
• Time to fill the tank
• Problems with subject panicking

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Skinfold Method

• The distribution of fat subcutaneously and
  internally is similar for all individuals within
  each gender
• SKF prediction equations are either
• linear (population specific)
• quadratic (generalized) regression models

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Skinfold Method cont..

• Common 4 -sites
• Cheap, easy to use, portable, all age groups,
  large numbers
• Errors occur selection of the site but single
  observer can produce reliable results
• Skin compressibility varies in individuals
• Excess fluid if repeated too many times
• Undress to get to certain sites

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Girth Measurements

• Useful in ranking groups
• Average error in BF between 2.5 and 4.0
• Can be used to target body fat changes from
  changes in abdominal girth
• 11 girths used to provide a muscular and
  non-muscular body profile
• Used to show differences in physique between
  athletes in different sports

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Bioelectrical Impedance Analysis(BIA)

• Examines impedance/opposition to electrical flow
  through tissues
• Greater flow through fat free mass and water
• Flow is low through fat tissue due to electrolyte
  content

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Factors affecting BIA values

• Maintenance of normal levels of hydration
• Affects the levels of electrolytes in the body
• Must fast for 4 hours! Eating, drinking and
  exercising will all affect the bodys hydration
  level
• Skin temperature affects whole body resistance
• Affected by ambient temperature (e.g. lower fat
  in warmer environments)
• Suggested that is worse than skinfolds

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Near Infrared Interactance

• Irradiating tissues with a beam of infrared
  radiation
• Measures the optical density of reflected
  radiation
• This is influenced by specific absorption of
  underlying tissue
• Specific equipment required (1500)
• Based on prediction equations include weight,
  height, age and sex
• Only possible to examine single sites
• Must be well shielded from extraneous light

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The Bodpod

• Same principle of whole body densiometry
• Computerised sensors determine the amount of air
  displaced
• Problems are calculated in the software (e.g.
  lung residual volume)
• Problems if you have a large bouffant hair style
  or hairy chest!

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Dual-energy X-ray Absorptiometry (DEXA)

• Measures differential attenuation of 2 x-rays as
  they pass through the body
• Distinguishes bone, FFM and FM
• Problems with DEXA
• Cost of machine
• Scanning area is small (190 x 60 cm)
• Clothes are important (e.g. cotton has an
  attenuation similar to fat)
• Edge differentiation is very difficult

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Scanning Techniques

• Good for estimation of a particular body
  compartment
• Methods include
• X-rays,
• Ultrasonography
• Computerised Tomography (CT)
• Magnetic Resonance Imaging (MRI)
• X-ray radiation poor image quality, inadequat
  precision
• CT good images, poor at extremities, VERY high
  radiation dose

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The Female Athlete Triad

• Who is affected by the condition?
• Aetiology of the condition
• Treatment of the condition
• Particular risks to exercising females

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What is the female athlete triad?

• A syndrome of medical conditions that can occur
  in females who are physically active
• Disordered Eating
• Amenorrhea
• Osteoporosis

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Disordered Eating

• Refers to ineffective eating behaviours that
  result in the in the altered consumption or
  absorption of food and that significantly
  impairs physical health or psychosocial
  functioning

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Disordered Eating cont.

• Fasting ? Decrease in BMR and LBM
• Diet pills ? Weight regain
• Diuretics ? Dehydration and decrease in
  electrolytes
• Laxatives ? Dehydration
• Sauna ? Dehydration
• Fat-free diets ? Lack of vitamins
• Exercise ? Risk of injury and dehydration
• Enemas ? Dehydration and GI problems
• Vomiting ? Dehydration, decrease in
  electrolytes, GI bleeds and dental problems

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Anorexia Nervosa

• Diagnostic criteria
• behaviour that is designed to produce marked
  weight loss
• the characteristic psychopathology of a morbid
  fear of becoming fat
• evidence of an endocrine disorder (amenorrhea)
• Physiology of the condition
• endocrine abnormalities
• cardiovascular abnormalities
• electrolyte and metabolic abnormalities
• haematological abnormalities
• GI disturbances

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Bulimia Nervosa

• Diagnostic criteria
• powerful and intractable urges to overeat
• avoidance of the fattening effects of food by
  inducing vomiting, abusing purgatives or both
• a morbid fear of becoming fat
• Physiology of the condition
• Electrolyte imbalance
• Tooth enamel
• Edema

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Amenorrhea

• Primary ammenorrhoea
• delayed onset of first menstrual period in girls
  with secondary sexual characteristics who are
  aged 16 yr
• Secondary ammenorrhoea
• absence of 3 or more consecutive menstrual cycles
• pregnancy and menopause must be ruled out
• decreased energy intake and excessive exercise

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Amenorrhea cont.

• Cause - large negative energy balance causes
  hypothalmic ammenorrhoea resulting in a decreased
  production of gonadotrophic releasing hormone
  (GnRH)
• Many athletes do not regard it as abnormal
• Reversal of amenorrhea is unpredictable
• Linked to loss of BMD

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Amenorrhea cont.
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Osteoporosis

• Disease characterised by a low bone mass and
  microarchitecural deterioration of bone tissue
• Normal BMD ? 1SD of normal
• Osteopenia BMD between -1 - 2.5 SD of Normal
• Osteoporosis BMD between -2.5 SD of normal

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Osteoporosis cont.
3D architecture normal bone
3D architecture osteoporotic bone
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Osteoporosis

• The principle cause of premenopausal
  osteoporosis in active women is decreased ovarian
  hormone production and hypoestrogenemia as a
  result of hypothalmic ammenorrhea (pi, ACSM,
  1997)

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Osteoporosis cont.

• Low bone mineral density throughout skeleton
• Not all amenorrheic athletes have low BMD
• Some studies report an increase in BMD in
  amenhorreic athletes resuming normal menses

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Treatment

• Increase energy intake by 250-350 kcal/day
• Decrease training by 10-20
• Hormone replacement therapy
• Oral contraceptives
• Calcium supplementation of 1500 mg/day
• Treatment may take several months to be
  successful and requires the compliance of the
  patient

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Who is at risk?

• Sports in which performance is subjectively
  scored
• Endurance sports emphasising low body weights
• Sports requiring body contour revealing clothing
  for competition
• Sports using weight categories
• Sports emphasising a preadolescent body build for
  success
• (ACSM, 1997)

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What can you do?

• Advocate health and well-being
• De-emphasise weight - discourage weighing
• Use normal weight role models
• Be aware of the signs of the Triad
• Dispel myths
• that thinner is better
• that ammenorrhoea is a normal sign of athletic
  training

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Nutrition and the Female Population

• Eating Attitudes Test
• Amenorrhoeic females consume 11 fat
• Eumenorrhoeic females consume 17 fat
• Vitamin B6 intake of less than 2/3 RDA
• Antioxidant vitamins to reduce exercise induced
  oxidative stress
• Minerals Calcium and Iron

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Calcium Requirement

• Adolescents and young adults require 1200 mg of
  calcium daily
• Adults past the age of 24 require 800 mg of
  calcium daily
• Osteoporosis
• Natural sources of calcium

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Nutrition and the Female Population

• Inadequate iron intake
• Females require a supplement of 5 mg of iron per
  day (extra 150 mg per month)
• 30-50 of women have significant dietary iron
  insufficiencies
• Source of Iron is Important

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Exercise-Induced Anaemia

• Sports anaemia is the reduction in Hb to levels
  approaching clinical anaemia that are believed to
  be due to intense training
• Heavy training causes???
• Increased iron demand
• Occurrence of gastrointestinal bleeding following
  long-distance running

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Weight Regulation (Obesity)

• Prevalence and costs of obesity
• Causes
• Health Risks
• Treatment and prevention

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Definition of Obesity

• W.H.O. (1998) defined obesity as a BMI ? 30
• (an excess accumulation of body fat)
• BMI Obesity Class
• Under weight lt 18.5
• Normal 18.5 - 24.9
• Overweight 25 - 29.9
• Obese 30 - 34.9 I
• 35 - 39.9 II
• ? 40 III

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Waist Measurements

• Waist measure taken at the level of the narrowest
  part of the torso, abdomen relaxed.
• Hip measure taken from maximum circumference of
  the hips/buttocks region.

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Prevalence of obesity by age and sex England 2002
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Prevalence of obesity, adults aged 16-24,
1986/87-2002, England
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Cost of obesity by related diseases
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Initial consequences of obesity

• increased incidence of hypertension
• increased incidence of hypercholesterolaemia
• increased incidence of NIDDM
• Excess weight is not considered a risk factor
  for CHD, but it is associated with an increased
  incidence of the above risk factors

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Diseases, illnesses, and other problems related
to obesity

• Hypertension
• Diabetes 80 of type II
• Osteoarthritis of knee
• Certain cancers
• Pulmonary dysfunction, gall bladder disease, and
  gout
• increased risk of CHD heart failure
• social discrimination
• problems with anaesthesia and surgery
• menstrual problems in women

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Causes of Obesity

• 1. Genetics
• 2. Eating behaviour and food intake
• 3. Energy expenditure
• 4. Hormones
• 5. Psychological influences
• 6. Smoking cessation
• 7. Metabolism

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Genetics

• Genetic makeup does not cause obesity, but may
  lower the threshold for the development of the
  disease
• Genetics contribute significantly to the
  variability in weight gain
• 25 of variation among people in BF and total
  fat mass determined by genetics
• 30 determined by cultural (transmissible) effect

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Genetics

• Research in mice shows that some people are
  genetically destined to become obese
• Mutation of a gene called obese or ob
• Gene disrupts signals that regulate metabolism,
  fat storage and appetite

Gene inside fat cell
Hormone enters blood stream
Hormone signals to hypothalmus
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Contribution of smoking and alcohol to obesity

• Many people, particularly women continue to smoke
  to control weight.
• There is no clear relationship between alcohol
  consumption and obesity, however, a lifestyle
  encouraging alcohol consumption may include a
  diet which promotes obesity.

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Psychological problems and obesity

• Obese patients rate themselves as more depressed
  (not clinical)
• Studies do suggest a relationship between size
  and depression
• This could be because depressed obese people are
  more likely to seek treatment

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Tackling obesity whose job?

• Government
• NHS
• Food industry
• Media
• Commercial weight loss groups

• Fitness/leisure industry
• Employers
• Schools
• Parents
• Individuals

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Beliefs about obesity

• Researchers asked a group of physicians and
  medical students to rate their overweight
  patients for a set of personal characteristics.
  They found that
• 97 judged them to be stupid
• 90 unsuccessful
• 90 weak
• 86 lazy
• 69 not nice
• 65 unhappy
• 60 weak-willed
• 54 ugly
• 55 awkward

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Weight Control Strategies

• Next week
• Dietary treatment
• Good nutritional practices
• Exercise and physical activity
• Surgical intervention
• Behavioural management
• Drug therapy
• Childhood obesity