Energy Balance and Body Composition Flashcards
Anabolism
- the build up of body compounds
- anabolic reactions include the making of glycogen, triglycerides, and protein; these reactions require differing amounts of energy
Catabolism
- the break down of body compounds
- Catabolic reactions include the breakdown of glycogen, triglycerides, and protein; the further catabolism of glucose, glycerol, fatty acids, and amino acids releases differing amounts of energy. Much of the energy released is captured in the bonds of ATP
Energy is released when…
a high-energy phosphate bond in ATP is broken. This energy is used to do the body’s work. The loss of a phosphate group from ATP results in the formation of ADP.
Energy is required for ATP synthesis. This enery comes from…
the breakdown of carbohydrate, fat and protein
The Body’s Energy Metabolism
Glycolysis, Pyruvate, Acetyl CoA = ENERGY
Glucose Breakdown - making energy from glucose
- glucose broken down to pyruvate and most often converted to acetyl CoA
- Pyruvate can be reconverted to glucose but acetyl CoA cannot
- Any compound that can be converted to pyruvate can be used to make glucose; any compound converted to acetyl CoA cannot be used to make glucose
- Acetyl CoA (from the breakdown of CHO) enters the TCA cycle, which ultimately makes energy along with the Electron Transport Chain
Glycolysis:
metabolic breakdown of glucose to pyruvate
Krebs Cycle (TCA cycyle)
where stored energy from CHO, fats, and protein is released. This happens when acetyl CoA is oxidized into ATP and Co2
Fat Breakdown
- Triglycerides become: 3 Fatty Acids (many carbons-long chains) & Glycerol “backbone”
- Acetyl CoA (2 carbon units) break off from Fatty Acids to yield energy
- Glycerol is left to become (a little) new glucose OR yield more energy
- Fat is inefficient source of glucose –> about 95% cannot be converted to glucose at all
Protein Breakdown
- protein is ideally used to maintain supplies of needed body proteins & will not be used for energy
- Deamination (loss of the amino NH2 group), if needed for energy or consumed in excess
- Most amino acids can be converted to pyruvate & glucose -> glucogenic
- some converted to acetyl CoA -> ketogenic
- Some enter TCA cycle directly
Energy Imbalance: Feasting
More energy consumed than expected
- excess is stored as fat
Exces carbohydrate
first stored as glycogen (limited capacity)
when stores are full, used for energy, displacing use of fat so fat is stored
excess fat
immediately routed to adipose tissue
stored until needed for energy
excess protein
the body possesses enzymes to convert excess protein to body fat, but this is very inefficient
research into the degree to which this occurs under normal conditions is ongoing
Food component: Carbohydrate
Is broken down in the body to:
And then contributes to:
Glucose
liver and muscle glycogen stores
Food component: Fat
Is broken down in the body to:
And then contributes to:
Fatty acids
Body fat stores
Food component: Protein
Is broken down in the body to:
And then contributes to:
Amino acids (first used to help replace body fuel; can also be converted to glucose or fat)
Nitrogen lost in urine
Energy Imbalance: Fasting
- Glycogen used first
- Glucose from glycogen stores; fatty acids from adipose tissue
- Liver glycogen exhausted within one day
- Glucose needed for the brain
- Brain, nerves, and RBC cannot metabolize fatty acids
Energy Imbalance: Fasting
- Protein breakdown and ketosis
- Protein breakdown provides glucose to fuel the brain
- Ketone body production increases as fast continues
- Lean tissue wasting slows but continues
Energy Imbalance: Fasting
- Slowed metabolism
- conserves fat and lean tissue
Ketone Bodies
acidic, water-soluble compounds produced by the liver from fatty acid fragments
Fasting: 12-15 hours
Glycogen stores run out
Fasting: 12/15-48 hours
Protein is main source of energy(90%)
- muscle breakdown (75-100g/d)
> 48 hours
- body shifts to energy most from ketone bodies
- basal metabolic rate declines
- slow steady muscle loss
Storage component: liver and muscle glycogen stores
Is broken down in the body to:
And then used for:
Glucose
Energy for the brain, nervous system, and red blood cells
Storage component: body fat stores
Is broken down in the body to:
And then used for:
fatty acids
energy for other cells
Body component (glycogen depleted): body protein
Is broken down in the body to:
And then converted to:
And then used for:
Amino acids
glucose
energy for the brain, nervous system, and RBC
Body component (glycogen depleted): body fat
Is broken down in the body to:
And then converted to:
And then used for:
fatty acids
ketone bodies
energy for other cells
hazards of fasting
- wasting of lean tissues
- impairment of disease resistance
- lowering the body’s temperature
- disruption of body’s fluid and electrolyte balances
Energy Balance: Change in energy stores =
energy in (kcalories) - energy out (kcalories)
Energy out - three factors to consider:
- Basal metabolism
- Energy for physical activities: factors influencing kcalories spend
- Energy to manage food
Basal Metabolism
- 2/3 of a sedentary person’s expenditure
- measurements: basal metabolic rate (BMR) and resting metabolic rate (RMR)
Energy for physical activities: factors influencing kcalories spent
- muscle mass
- body weight
- activity: duration, frequency, and intensity
Components of Energy Expenditure
30-50% Physical Activities
10% Thermic effect of food
50-65% Basal metabolism
Factors influencing energy expenditure
- Gender: higher BMR with growth
- Growth: increased BMR with growth
- Age: BMR declines during adulthood
- Physical activity: energy needs vary by activity
- Body composition and body size: higher BMR for taller or heavier persons
Estimating energy requirements
- Equations for estimated energy requirements
- Dependent upon age, gender, weight, height, and physical activity
Eating Disorders
- Estimated to affect 6 percent of females and 3% of males
Anorexia nervosa
Bulimia nervosa
Binge eating disorder - characteristics of disordered eating (restraining or binge eating, purging, fear of fatness and distortion of body image)
Causes of eating disorders
- Sociocultural (pressure to be thin, view of healthy body weight as overweight)
- Psychological (use of unhealthy actions to lost weight, energy restriction followed by binging, pattern of weight cycling)
- neurochemical
Eating Disorders - Vulnerable Groups
- athletes and dancers at greater risk
- risk factors for athletes:
Young age, pressure to excel in a sport, focus on achieving “ideal” body weight, sports that focus on aesthetic appeal (gymnastics, dance, figure skating), unhealthy weight loss dieting at a young age
Anorexia Nervosa
- female, middle-or upper-class, perfectionist
- sees self as too fat regardless of weight
- treatment aspects (deal with food and weight, deal with relationships with self and others)
Bulimia Nervosa
Binging and purging
- binging done in secret
- purging methods include cathartic or emetic (bother have serious physical consequences)
- person feels guilt (aware of consequences of behaviour)
- binge eating disorder without purging
- treatment involves helping client gain control of behaviour
