Unit 1; Nutrition & Energy Balance Flashcards
What are the two sides of the scale for energy balance?
Energy input vs energy output
If energy output > energy input, what happens to weight?
Weight Loss (Negative balance)
If energy input > energy output, what happens to weight?
Weight Gain (Positive balance)
What other aspects, other than energy input & energy output, can add to the complexity of energy balance? Give 4 examples.
Genetics, psycho social, food availability, environmental factors
Define Energy Input
The calories that our body needs that come from the food we eat.
List the 3 types of macronutrients that are sources of energy.
Carbohydrates, proteins, fats.
What other substance can also be an energy source and how many kcal/g does it contribute?
Alcohol = 7 kcal/g
How many kcal/g do carbohydrates have?
4 kcal/g
How many kcal/g do proteins have?
4 kcal/g
How many kcal/g do fats have?
9 kcal/g
How many calories per day is recommended for adults?
2000-3000
What are 4 factors that can affect energy input?
Neuro-endocrine factors (neurotransmitters, hormones, etc), filling/distention of stomach (effects of dietary fibre), social/psychological factors (anxiety, depression), food availability & appeal
Define Satiation/Satiety
Neural state that leads one to decrease or stop eating (loss of drive/desire to eat) [Occurs between meals]
Define Hunger
Physiological drive to get food & eat
Define Appetite
Psychological desire to eat (more conditional than hunger)
How do neuro-endocrine factors influence energy intake?
Feeding behaviour, energy balance, & the production/secretion of hormones
What hormones promote increased food intake?
Ghrelin, Neuropeptide Y (NPY/ NYP)
What hormones promote decreased food intake?
Leptin, Peptide YY (PYY), Cholecystokinin (CCK), Apolioprotein A4 (apoA IV)
What is the role of the hypothalamus in eating?
Central integrator of circulatory signals (hormones) & neural signals from other brain areas
What is the role of leptin & where is it produced?
It is a satiety signal which is produced by the adypocytes (fat cells) & signals brain which in turn lowers NPY signals.
What is the role of NPY & where is it produced?
Signals neurons to be more active which increases hunger signals and is produced in the brain.
What is the role of Ghrelin & where is it produced?
Activates NPY system in turn increasing hunger and produced in stomach.
What is the role of PYY & where is it produced?
Produced in the Gi tract in response to meal.
What is the role of CCK & where is it produced?
Produced in Gi tract in response to meal.
What is the role of apoA IV & where is it produced?
Produced in Gi tract in response to meal.
What do the hormones do when food is consumed and digested?
When food is consumed & digested the gut is stimulated to produce PYY & CKK which contribute to satiety signals in the brain leading to decreased activity of NPY
On the hormone level, what happens a couple hours after a meal?
Nutrients become stored in the fat cells (adipocytes), which increase secretion of leptin. Leptin signals to the hypothalamus to decrease activity of NPY reinforcing satiety.
What happens in the body on a hormonal level when one is feeling hungry?
Ghrelin is secreted by the empty stomach (gastric & duodenal cells) which signals the hypothalamus to increase activity of NPY. After a long time without food consumption, the adipocytes greatly decrease their secretion of leptin.
List the 3 ways that energy is used in the body (energy output).
Resting energy expenditure (REE), thermic effect of food (TEF), physical activity (PA).
What is the approximate % total energy output for basal/resting energy expenditure?
65%
Give examples of when your body uses a minimal amount of calories?
Awake, resting, fasting, & in warm, quiet low-stress environments
Is REE or BEE easier to measure and why?
Resting energy expenditure (Only need to fast for 4 hours instead of 12hrs)
What does BMR stand for?
Basal metabolic rate
What does RMR stand for?
Resting metabolic rate
What is the unit for BMR & RMR?
kcal/ kg body weight/ hour
What period of time is BEE & REE measured over?
24hr period
How does a greater body size affect REE?
Increases REE
How does a greater proportion of lean body mass (more muscle) affect REE?
Increases REE
How does older age affect REE?
Decreases REE
How does gender affect REE?
Increased REE in men
How does having higher thyroxine levels (thyroid hormone) affect REE?
Increased REE
How does fasting affect REE?
Decreased REE
How does a fever affect REE?
Increased REE
How does pregnancy/lactation affect REE?
Increased REE
How is % REE for each body system change for infants compared to adults?
Adults have an even % contribution to each body system (20% brain, 20% kidney & heart & adipose, 20% muscle, 20% liver, 20% other) compared to infants where the brain contributes a larger amount (44% brain, 15% kidney & heart & muscle, 15% liver, 25% other)
What is the approximate % total energy output for thermic effect of food?
10%
When is there an acute increase in energy expenditure due to the TEF?
After a meal
What can influence the TEF energy expenditure?
Meal size, macronutrient composition, spices (mustard/peppers increase TEF of a meal by 10-30%)
What is the relative ratio of TEF energy expenditure for each macronutrient?
1 fat: 1.5 carb: 3 protein
What factor is associated w/ a lower TEF & why?
Obesity due to lower insulin sensitivity
What is the approximate % total energy output for physical activity?
25% (Highly variable among individuals)
What other things can diet influence & how?
Disease risk through chromatin modifications
What are 3 methods to assess body mass and fat?
BMI, skin-fold thickness, underwater weight
What contributes to Lean Body Mass?
Body muscle
What contributes to Fat-Free Mass?
Lean body mass + water & minerals
What contributes to Body Weight?
Fat-free mass + fat mass
Define the ideal body weight
The weight range that maximizes health (minimizes risk of diseases that affect lifespan & quality of life)
At which BMI range does the least risk for mortality occur?
18.5 - 24.9
What are some reasons that obesity has increased in the past few decades?
Increased availability of high energy foods, decreased physical activity. Both in combination with genetic predisposition.
What is the statistic for how many Canadians are overweight?
~1:3
What is the statistic for how many Canadians aren’t getting enough exercise?
~8:10
What is the statistic for how many people maintain weight loss over a 5 year period?
~1:20
What BMI has weight-associated health risks, especially in males?
> 25
What BMI is considered obese?
> 30
What body fat % indicates obesity in each gender?
25% for men, 35% for women
What measure is a good indicator of obesity & co-morbidites?
Waist to Hip Ratio
Define metabolic syndrome
The condition in which a person has a combination of 3+ metabolic problems (often associated w/ obesity)
What are the 3 conditions included in metabolic syndrome?
Atherogenic dyslipidemia (ex. high serum cholesterol), hypertension, abnormally high serum glucose
What waist circumference indicates obesity in each gender?
> 100cm male, >90cm female
What are the 2 types of fat?
Essential fat, & fat storage