Body Composition and Weight Control

• These are study notes about Body Composition and Weight Control

Body Composition Models

• Two-compartment models partition the body into fat and fat-free mass
• Three-compartment models partition the body into fat mass, total body water, and fat-free solid
• Four-compartment models partition the body into fat mass, total body water, bone mineral, and residual mass
• Fat-free weight is 55-96% of total body weight
• Fat is approximately 4-45% of total body weight
• The body is composed of 48% muscle, 16% bone, 14% skin, 9% blood, and 13% organs
• Water makes us 72-74% of the fat-free weight with protein coming in second at 19-21%

Key Terms

• Body composition is the partitioning of body mass into FFM (weight or percentage) and fat mass (weight or percentage)
• Fat-free weight is the weight of body tissue excluding extractable fat
• Densitometry is the measurement of mass per unit volume

Methods for Measurement of Body Composition

• Underwater weighing involves water being equal to the volume of the object entering the water
• Volume is proportional to mass
• Archimedes reasoned that the loss of weight in water is the weight of the water displaced
• Archimedes' principle states that a submerged object experiences an upward buoyant force equal to the weight of the fluid displaced by the object
• Based on this principle, the volume of any object, including the human body, can be measured by determining the weight lost by complete submersion underwater
• A more lean, muscular individual tends to sink with underwater weighing, while people with more fat will tend to float
• Air Displacement Plethysmography (Bod Pod) measures body volume, which is directly related to air displaced from the chamber
• Boyles Law states that the relationship between pressure and volume is inverse
• The Bod Pod calculates total body density as a produce of body mass per unit of volume
• The Bod Pod is known for comfort, ease of use, and efficiency
• Dual-Energy X-Ray Absorptiometry (DEXA) measures uses an x-ray to measure three compartments
  • Fat mass
  • Lean soft tissue, also called lean body mass
  • Bone mineral density
  • Each component has a characteristic ability to absorb energy
• DEXA is considered the gold standard
• Skinfolds are a measure of the double thickness of the skin plus the adipose tissue between parallel layers of the skin
• Skin thickness varies slightly among individuals indicating the thickness of subcutaneous fat
• Skinfold calculations are also based on age and gender, since older populations have less subcutaneous fat
• Skinfold measurements tend to slightly underpredict %BF by 3-5%
• The greatest error using skinfolds is improper location of the skinfold site

Body Mass Index

• Body Mass Index or BMI is calculated by taking weight in kilograms and dividing it by height in meters squared, (WT ÷ HT2 (kg-m-2))
• Below are some cut off points for BMI
  • Under 18 years acceptable Male/Female is 5-84th percentile, Male/Female Overweight is 85-94th percentile, and Obesity is when it is greater than the 95th percentile, or BMI greater than 30
  • Equal to or Over 18 years, Acceptable Male/Female is 18.5-24.9 BMI, Male/Female Overweight is 25.0-29.9 BMI
• Below are some Obesity ranges for adults
  • Class I = 30-34.9 BMI
  • Class II = 35-39.9 BMI
  • Class III = ≥40 BMI
• Waist circumference is measured with a tape measure, to the nearest centimeter
• Hip circumference is measured at the largest site
• Both measures should be taken while the individual is standing and without clothes
• The W/H ratio is stronger a predictor for diabetes, coronary artery disease, and overall death risk than body weight, BMI, or %BF in adults
• The average value for females aged 17-39 years is 0.80, this increases with age to above 0.90
• Comparable averages for males range from 0.90 to 0.98
• Values equal to or greater than 0.84 for females and ≥0.99 for males 20-60 years and, ≥0.90 and ≥1.03 for females and males, respectively, 60–69 years signal a high risk for metabolic disease
• Bioelectrical Impedance measures total body water so estimates can be made of body density and FFW
• The ability to conduct the electrical current is directly related to the amount of water and electrolytes in the various body tissues
• Electrical current flows more easily in fat-free tissue (less resistance) than in fat tissue (impedance) since the fat-free tissue has a higher percentage of water and electrolytes
• Individuals with more fat-free weight (FFW) have lower resistance values, and those with more fat weight have higher resistance values

Body Fat Percentages

• Recommended body fat range for women over 56 years is 25-38% and is classified as obese
• Recommended body fat range for women 35-55 years is 23-38% and is classified as obese
• Recommended body fat range for women 34 years and younger is 20-35% and is classified as obese
• Athletic women generally range from 12-22%
• Essential fat in women is 8-12%
• Minimal body fat for women is 10-12%
• Recommended body fat range for men over 56 years is 10-25% and is classified as obese
• Recommended body fat range for men 35-55 years is 10-25% and is classified as obese
• Recommended body fat range for men 34 years and younger is 8-22% and is classified as obese
• Athletic men generally range from 5-13%
• Essential fat in men is 3-5%
• Minimal body fat for males is 5%

Adipose Cells

• Fat cells do not go away, 30-50 million is normal while 75+ million signifies obesity
• Adipose cells can be white, beige, and brown
• The mitochondria use fat droplets to HEAT the body
• Females have approximately 50% more fat cells than males
• Hypertrophy causes bulging in fibrous tissue creating cellulite
• Hyperplasia occurs once hypertrophy reaches its limit, the adipocyte stimulates cell division and maturation in precursor cells, increasing the amount

Metabolic Changes From Fat

• Diabetes mellitus type 2
• Insulin resistance
• Gallbladder disease
• Hypertension
• Coronary heart disease
• Stroke
• Certain cancers like breast and colon
• Dyslipidemia/hyperlipidemia
  • Elevated LDL-C
  • Elevated TG
  • Decreased HDL-C
• Impaired fertility
• Other reproductive problems
• Gout
• Digestive diseases

Changes From Mass Fat

• Osteoarthritis
• Sleep apnea
• Breathlessness/respiratory problems
• Low back pain
• Skin stretch marks
• Congestive heart failure

Calories in vs Calories out

• Caloric balance includes food ingestion
• A certain amount of caloric balance goes toward basal or resting metabolic rate
• Calories are used for thermogenesis, work or exercise and are excreted in waste
• If food and drink exceeds energy expenditure, weight is gained
• Episodic Appetite Signals include appetite stimulating and inhibiting hormones with influence by gastrointestinal tract
• Tonic Appetite Signals includes energy demand, drive to eat, intake, and leptin/adipokines

Impact of Exercise

• One workout per day is no impact on weight loss and appetite
• An activity induced negative balance is tolerated for 1-2 weeks
• Food intake increases 30-60% of energy expended during exercise after 1-2 weeks of consistent workouts
• Appetite response is not sex specific to exercise

Exercise Training

• Exercise trained males experience appetite suppression by exercise
• There is not enough information and data to determine similar result in women
• If training creates fat free mass, then there will be more hunger
• If training creates less fat mass, there will be a decrease in leptin resulting in increased satiety

Basal Metabolic Rate

• Basal metabolic rate (BMR) and resting metabolic rate (RMR), is the energy required to sustain body's vital functions
• Difference between BMR and RMR is purely technical depending on the source
• 29-32% of BMR comes from the liver
• 19-21% of BMR comes from the brain
• 10% of BMR comes from the heart
• 9% of BMR comes from the lungs
• 7% of BMR comes from the kidneys

Basal Resting Metabolic Rate Equations for Men and Women

• Below is the equation for males
  • RMR = 88.362 + (4.799 × HT) + (13.397 × WT) – (5.677 × AGE)
• Below is the equation for females
  • RMR = 447.593 + (3.098 × HT) + (9.247 × WT) – (4.330 × AGE)
  • *Eighty-five percent of all normal subjects have estimated RMR values within 10% of their measured values
• When an individual has severe caloric restrictions, BMR can decrease as much as 10-20% after several weeks
• Researchers speculate that the decline in BMR is the body's protective response
• EPOC increases metabolism by exercise
  • 35 kcal after 1 hour of resistance training
  • 20-30 kcal after continuous exercise

Factors Leading to Weight Loss

• Four things to target in weight loss plan
  • Lose body fat with consideration to visceral abdominal fat
  • Preserve fat free mass
  • Maintain/improve health
  • Maintain/improve athletic performance
• To get the most of your weight loss
  • Focus on dynamic aerobic endurance, weight-bearing, or non-weight bearing dynamic resistance training

Diet and Weight Loss

• Very low caloric intake (400-800kcal) helps lose weight by 50% fat and 50% fat-free mass
• Low caloric intake (800-1200kcal) helps lose weight by 75% fat and 25% fat-free mass
• Somewhat Low caloric intake (1200-1500kcal) helps lose weight by 90% fat and 10% fat-free mass
• Little evidence suggests that exercise produces weight loss equivalent to what can be achieved with dietary modification
• You cannot outwork a bad diet
• DIet is 87% of the battle
• Resistance Training increases total weight loss with maintaining lean mass

Weight Loss Guidelines

• Diets should provide 500-1000kcal below normal pre-diet intake. Should not be lower than RMR
• 45-65% carbohydrate
• 10-35% protein
• 20-35% total fat (as low as possible)
• 45-60 minutes of exercise is needed to prevent weight gain