NUTR 315 CH10: Energy Balance and Weight Management

energy balance

the relationship between energy intake and energy expenditure

when is positive energy balance desired?

during growth stages such as pregnancy, childhood, or when body weight needs to be restored after disease or injury

when is negative energy balance desired?

when energy stored in the body is used to make up for shortfall in energy intake; desired in adults when body fat exceeds healthy levels

what is body weight?

results from a dynamic equilibrium between energy intake and energy expenditure

how can calorie content be directly measured?

bomb calorimetry

how does a bomb calorimeter measure calorie content?

by burning food to raise the temperature of water, 1kcal= the amount of heat needed to raise the temperature of 1kg of water by 1 Celsius

heat of combustion

heat obtained from the sample is compared with the heat obtained from the combustion of a similar amount of standardizing material whose calorific value is known

what does bomb calorimetry not take into account?

digestibility, nitrogen combusted

how do you calculate physiological fuel value?

net heat of combustion x coefficient of digestibility

how are calories calculated?

multiply each gram of nutrient by its physiological fuel value

proximate analysis

says that energy value is an estimate because different foods have different digestibility (ex. fiber is a carbohydrate but does not provide the same amount of usable energy as digestible carbohydrates)

main purposes for energy expenditures

basal metabolism (BMR), physical activity, digestion, absorption, and processing of ingested nutrients

what is a minor component of energy balance?

non-exercise activity thermogenesis (NEAT: heat production in response to non-voluntary activities) ex. shivering, maintaining muscle tone

what is basal metabolism?

energy required at rest to maintain life, accounts for 60-70% of total EE and is regulated by thyroid hormones

what are some factors influencing BMR?

body size, body composition, gender, age, hormones, and sleep

Physical activity increases energy expenditure above basal energy needs by what percentage range?

25-40%

what is the thermic effect?

heat generated as the result of a meal that accounts for 5-10% of daily energy

obligatory thermogenesis

unavoidable losses due to absorption, transport, storage, and synthesis of protein and fat

is TEF higher in protein-rich meals or carbohydrate/fat- rich meals?

TEF is higher for protein-rich meals because it takes more energy to metabolize amino acids into fat than to convert glucose into glycogen or absorbed fat into adipose tissue

NEAT (non-exercise activity thermogenesis)

stimulated by cold environment (ex. shivering/ posture), uses brown adipose tissue to to generate heat for body instead of creating ATP (adults have little brown adipose)

what is direct calorimetry?

estimates EE by measuring the amount of body heat a person releases in an insulated chamber surrounded by water

what is indirect calorimetry?

the most common method of measuring EE that uses the link between the body’s use of energy and the amount of O2 consumed and CO2 produced by collecting expired air from an individual during a specific amount of time

what is obesity?

defined as >120% of ideal body weight

what are some factors of obesity?

family history of chronic disease, pattern of fat distribution, and current health status

what is the calculation for body mass index (BMI)?

body weight (kg)/ height (m)²

what is an acceptable BMI vs overweight?

acceptable range= 18.5-24.9 and obese= 30-39.9

what are some problems associated with obesity?

increased risk for chronic diseases (ex., diabetes, gallstones, hypertension), economic (health care), psychological health (discrimination/negative self-image)

what are some causes of obesity?

genetics (body type and EE), and behavior 9energy intake and output balance)

appetite

physiological drive to eat

hunger

the sensations that initiate food-seeking behavior (energy based)

desire to eat

cognitive or sensory-based motivation to initiate an eating event

fullness

motivation to terminate an eating event

what is the purpose of appetite?

to match EI with EE and maintain a predetermined body-weight

what is cholecystokinin (CCK)

released by the duodenum in response to food intake, particularly fat and protein

ghrelin

‘hunger hormone’ that is secreted by endocrine cells in the gut as a peripheral stimulant of food intake, concentration rises leading up to a meal

leptin

‘satiety hormone’, secreted by fat cells and suppresses your appetite

underweight

less than or equal to 15% below desired weight or 18.5 BMI caused by eating disorders, cancer, infectious disease, excessive physical activity, or digestive tract disorders

anorexia nervosa

fear of gaining weight and refusal to maintain normal body weight

bulimia nervosa

recurrent episodes of binge eating 2x/wk for 3 months

binge eating disorder

recurrent episodes of binge eating 2x/wk for 6 months

OSFED/UFED

patients meet some, but not all criteria for diagnosis of AN, BN, or BED