Week 2: Energy balance, body composition, disease Flashcards
Energy IN
Food consumption
Energy OUT
- Basal metabolic rate (BMR)
- Exercise activity thermogenesis (EAT)
- Non-exercise activity thermogenesis (NEAT)
- Thermic effect of food (TEF)
% of total daily energy expenditure from BMR
65
% of total daily energy expenditure from NEAT
20
% of total daily energy expenditure from EAT
10
% of total daily energy expenditure from TEF
5
Resting energy expenditure (RER)
Amount of energy required by the body in the resting condition (less accurate)
Basal metabolic rate
Amount of energy needed to maintain basic life metabolic processes at rest (more accurate)
Factors that affect BMR
- Sex
- Diet
- Pregnancy
- Age
- Fat free mass
Sex and BMR
Females have lower BMR
Age and BMR
Lower BMR as you age
Fat free mass and BMR
More muscle you burn more calories
Thermic effect of food
Energy cost during food digestion, absorption and storage
Non-exercise activity thermogenesis (NEAT)
Portion of daily energy expenditure resulting from spontaneous physical activity that is NOT the result of voluntary exercise ex. fidgeting
Exercise activity thermogenesis (EAT)
Calories burned when engaging in purposeful physical activity
Metabolic equivalent of task (MET)
Ratio of the rate of energy expended during an activity to the rate of energy expended at rest
What is 1 MET?
Amount of O2 consumed while sitting at rest
Measuring energy expenditure
Indirect and direct calorimetry
Indirect calorimetry
Wear a mask that measures ratio of consumption of O2 and release of CO2
Direct calorimetry
Measures heat dissipation
Calorie
Energy required to increase temp of 1 g of water by 1 degree celcius
Obesity
Progressive chronic disease characterized by abnormal or excessive fat accumulation that impairs health
Body mass index (BMI)
Universal definition of overweight and obesity
BMI equation
Mass (kg)/height (m2)
BMI- underweight
<18.5
BMI- normal weight
18.5-24.9
Overweight
25.0-29.9
BMI- obese class I
30-34.9
BMI- obese class II
35.0-39.9
BMI- obese class III
> 40
BMI limitations
- Body composition
- Fat distribution
- Ethnic groups and age
Direct methods of measuring BMI
MRI, CT, DXA
Indirect methods of measuring BMI
Lab based: hydrostatic weighing, BodPod
Field methods: Skin folds, BIA
Subcutaneous adipose tissue
Makes up 80% of total body fat
Energy storage, adrenergic stimulation and endocrine regulation
Visceral adipose tissue
Makes up 5-20% of total body fat
Protects organs
Negative impacts of visceral body fat
Secretes proinflammatory cytokines
Increased risk of metabolic and cardiovascular disease
Theories regarding how visceral adipocytes mediate insulin resistance
- Pro-inflammatory cytokines
- Spillover hypothesis
- Portal hypothesis
Pro-inflammatory cytokines
Alter hepatic function, insulin sensitivity, cytokine production
Spillover hypothesis
When SAT reaches its limit for expansion, excess energy is stored as VAT resulting in the overdevelopment of ectopic fat stores and metabolic perturbations
Ectopic fat
Storage of fat in tissues other than adipose tissue such as the liver, heart, muscle and pancreas
Interferes with organ function and is associated with insulin resistance
Portal hypothesis
Liver is directly exposed to FFA and cytokines released from visceral fat tissue leading to development of hepatic insulin resistance and T2D
Waist circumference of men
More likely to accumulate visceral fat leading to a greater risk of CVD (android obesity)
>102cm =increased risk
Waist circumference of women
Gynoid obesity
>88cm = increased risk
Why has obesity increased?
Energy in increased
NEAT has decreased
Why has energy in increased ?
Bigger portion sizes
Easier access
Why has NEAT decreased?
Occupations involving less PA and more sitting
Set point theory
Human body has a predetermined weight or fat mass set point range; there are compensatory physiological mechanisms that resist deviation from set point
Factors that alter set point
- Genetics
- Epigenetics
- Obesogens
- Diet and PA
- Disease
Unregulated zone
When we are sedentary there is a mismatch btwn energy intake and energy expenditure resulting in high body weight
Regulated zone
When we increase energy expenditure our energy intake can increase while our body weight actually declines
Obligatory thermogenesis
Necessary accompaniment of all metabolic processes involved in maintenance of body in living state
- decreased metabolically active tissue
- reduced energy cost of movement
- decreased postprandial response
Adaptive thermogenesis
Physiologicial mechanisms employed to maintain weight
Underfeeding associated fall in resting and and non-resting energy expenditure independent of changes in FFM and FM
Spendthrift phenotype (compensators)
Subjects who respond to overfeeding with increased spontaneous PA
(less susceptible to obesity)
Thrifty phenotype (non-compensators)
Subjects who do not respond to overfeeding with increased NEAT
(more susceptible to weight gain)
Hard gainers
People who can eat whatever they want and not gain weight bc when they overeat their NEAT increases (ex. fidgeting can burn an extra 600kcals a day)
Why is protein important for maintaining weight?
Thermogenic effects
Promotes fat loss
Nutrient dense
Poor lipogenic substance
Preserves lean tissue
Increased satiety
Roles of insulin
- Stimulates glucose uptake from blood into tissues (lowers blood glucose)
- Stimulates glycogen formation
- Suppresses release of fatty acids from adipose tissue
- Inhibits production of ketones in liver
Glucagon
Promotes an increase in blood glucose levels and stimulates glycogen breakdown
Carbs effect on insulin secretion
Potent effect
Protein effect on insulin and glucagon
Elevates both
Fat effect on insulin
NO effect
Carbohydrate insulin model- a calorie is not just a calorie
Dietary quality can change hormonal responses to shift partitioning of calories consumed in meal toward deposition of fat tissue, causing few calories to remain available in the blood stream for the rest of the body, driving hunger and overeating
Study 1- Insulin secretion
Only decreased in RC diet
Study 1- fat oxidation
Only increased w RC diet
Study 1- body fat loss
More cumulative body fat loss with RF diet
Study 1- energy expenditure
Only decreased in RC diet
Final conclusion of study 1
The effects of the RC and RF diet are statistically insignificant and therefore a calorie is just a calorie
Study 2- conclusions
Ultra-processes diet caused increased ad libitum (eat whatever) energy intake and weight and fat mass gain
Summary of the two studies
Both increased carbs and fats increase weight
Refined carb intake may accelerate weight gain
When is a calorie just a calorie
When it comes to weight loss