Energy Expenditure, Body Composition, and Healthy Weight

energy balance should equal…

0 (to maintain weight)

energy balance > 0

indicates weight gain

energy balance < 0

indicates weight loss

basal metabolic rate (BMR)

energy needed for basic body functions (1200-1800 kcal/day)

thermic effect of food (TEF)

energy used to digest absorb and process food (100-250 kcal/day)

total daily energy expenditure (TDEE)

~ 1800-2500 kcal/day

how do we measure energy expenditure?

direct calorimetry

doubly labeled water (DLW)

gold standard method for measuring total energy expenditure (TEE)

Harris-benedict equations

formula used to calculate BMR

Mifflin-St. Joer equations

calculates the number of calories burned when the body is at rest

body weight assessment pros

• measurable outcome

• can increase awareness of weight trends

• prompt self-regulation behavior

• identifies weight change

• inexpensive, accessible

body weight assessment cons

• doesn’t measure body fat and body composition

• overreaction to individual measurement

• may increase preoccupation with weight

• don’t assess dietary quality

BMI formula

mass (kg) / height (m²)

skin fold thickness pros

• inexpensive

• quick and portable

• noninvasive and well tolerated

• useful for tracking change overtime

• can estimate body fat % using population-specific equations

• provide info about subcutaneous fat distribution

skinfold thickness cons/limitations

• technician dependent

• measurement error between technicians

• requires accurate landmarking and site selection

• less accurate at very high or very low body fat levels

• equations not generalized to individuals

• don’t directly measure visceral fat or total body fat

• less suitable when sites are hard to access or identify

bioelectrical impedance (BIA) pros

• quick, easy, inexpensive

• noninvasive

• portable

• estimates body fat and free-fat mass

bioelectrical impedance (BIA) cons

• affected by hydration status as well as food intake

• results vary among devices

• requires population-specific prediction equations

• less accurate at extremes of body size or body composition

underwater weighing pros

• noninvasive

• relatively accurate when done right

• useful for research and validation

• strong physiological basis for estimating body fat

underwater weighing cons

• special equipment

• proper technician

• lung volume

• not practical for field assessment

bod pod pros

• quick, noninvasive

• body volume using air displacement

• bone-density equation

• research and clinical assessment

bod pod cons

• expensive

• special training

• less accurate at extreme body sizes

DEXA pros

• accurate, quick

• provide regional data

• provide whole body assessment

DEXA cons

• expensive equipment

• small radiation exposure

• body size limitation

what is leptin’s role?

signal energy stores to hypothalamus; promote satiety and increased energy expenditure

what is insulin’s role?

released in response to food, promote glucose uptake, long term energy signal to brian

adiponectin’s role

enhance insulin sensitivity, promote fatty acid oxidation, anti-inflammatory effects

ghrelin’s role?

hunger promoter