Ch 10 Energy Balance - LOs

energy balance

the relationship between energy intake and energy expenditure

energy equilibrium

when calories consumed matches the amount of energy expended

positive energy balance

when energy exceeds energy expenditure = weight gain

negative energy balance

when energy intake is less than energy expenditure = weight loss

situations where positive energy balance is desired

pregnancy, childhood growth

calorie

heat required to raise 1 g of water by 1 degree C

kilocalorie

heat required to raise 1 kg of water by 1 degree C

• energy is lost as heat or used for digestion process

• calories in/out rule of weight regulation is true but oversimplified

why do humans not digest all the calories they eat?

obesity trends among US adults

rise over the past 30 years

basal metabolic rate (BMR)

• minimum amount of energy expended in fasting to keep a resting, awake body alive in a warm quiet environment

  • “cost of living” ~ heartbeat, respiration, etc.

resting metabolic rate

same as BMR, but not fasting

BMR for women

0.9 kcal/kg per hr

BMR for men

1.0 kcal/kg per hr

BMR amount of total energy expenditure

60-70%

how much does BMR vary?

25-30%

factors that contribute to variance in BMR

• muscle mass

• hormones

• body surface area

• etc.

how much BMR declines after age 30

1-2%

physical activity (exercise)

• calories burned from deliberate exercise

  • can range from 0 to several hundred per day

thermic effect of food

• energy used to digest, absorb, transport, store and metabolize

percentage thermic effect of food in energy consumed

5-10% (100-300 calories)

TEF for protein rich meal

20-30%

TEF for carbohydrate rich meal

5-10%

TEF for fat rich meal

0-3%

non-exercise activity thermogenesis (NEAT)

• varies greatly, but accounts for hundreds of calories burned per day

• includes non-deliberate physical activity

  • fidgeting, shivering, posture, stairs, housework

brown adipose tissue

• source of NEAT, mainly in infants

  • small amount in adults

  • heat generating tissue that is 5% of infant body weight

direct calorimetry

person in a sealed chamber where you measure heat

indirect calorimetry

measure gases ~ O2 in and CO2 out

hunger

physiological drive to find and eat food

appetite

psychological drive to eat

hypothalamus

• communicates with endocrine and nervous system

• integrates internal clues of blood glucose levels, hormone secretions, and sympathetic nervous system

signals stimulate satiety center

stop eating

signals stimulate feeding centers

eat more

satiety process

1. flavor of food

2. knowing a meal was just eaten

3. influence of stomach and intestinal expansion and activity

4. influence of nutrient use in the liver and related communication with hypothalamus and other brain regions

5. conscious thinking takes place in the brain’s cortex and can overcome hunger and satiety signals

factors that contribute to satiety (fullness)

• sensory aspects of food

• knowledge that food was eaten

• chewing

• expansion of stomach and intestines

• effects of digestion, absorption, and metabolism

• hormones

leptin

• hormone produced by adipose

• helps monitor stored energy

hunger response

empty fat cells » no leptin » appetite

satiety response

full fat cells » leptin increase » no appetite

body mass index (BMI)

• weight for height standard

• convenient

• used for males and females

• body weight (kg)/height² (m) OR body weight (lb) *703/height² (in)

underweight

BMI <18.5

healthy weight

BMI 18.5 to <25

overweight

BMI 25 to <30

• health risks may be seen

• not necessarily a marker of excess fat

obese

> 30

limitations of BMI

does not account for many factors:

• sex

• age

• bone/muscle density and mass

• genetics

• ethnicity

body roundness index

uses height and waist circumference

pros of the body roundness index

• might be better at assessing risk in different body types

• visceral adipose tissue is strongly associated with disease risk (diabetes, CVD, etc.)

cons of body roundness index

• measuring waist is harder than you think

• needs more validation (recent findings)

desirable amount of body fat in men

8-24%

desirable amount of body fat in women

21-35% = need more fat to support pregnancy/lactation

body fat content measurement methods

• dual energy x-ray absorptiometry (DEXA) - most accurate

• water or air displacement

• skin folds

• bioelectric impedance

obesity risk for children with no obese parents

10%

obesity risk for children with one obese parent

40%

obesity risk for children with two obese parents

80%

role of genetics in weight gain

• genes account for 40-70% of weight differences

  • body type, metabolic rate, factors that affect hunger and satiety

• even when identical twins are raised apart, they show similar weight gain patterns

“thrifty metabolism”

some people may use energy more frugally; store fat more readily

set point theory

• the body appears to have a genetically predetermined body weight or fat content that is closely regulated

• when energy intake is reduced:

  • thyroid hormone secretions fall, slowing metabolism

  • body becomes more efficient at storing fat

• body is somewhat resistant to weight gain, but is weaker mechanism

percentage of people who go on a diet and maintain weight loss for 3-5 years after the diet ends

5%

roles of the environment on weight

• couples and friends tend toward similar weights

• many factors play a role in food intake (cultural, economic, etc.)

  • genes and environment both matter

amount of time that commercial diets leave lasting weight loss

5%

how quickly people return to original weight after a commercial diet

3-5 years

characteristics of a successful diet

• 1-2 lbs a week

• normal food and activity levels

• reasonable and sustainable

500 kcal/day

energy intake decrease required to lose 1 pound a week

can be done through calorie restriction, physical activity or combination

3500 calories

deficit required to lose one pound

low energy density foods

most successful long-term diets

regular physical activity

• does not need to be high intensity

• good to add some resistance/higher impact exercise

behaviors of people who maintain a healthy weight

• eat a low-fat, high-carb diet

  • 25% fat intake

  • 56% carb intake from fruits, vegetables, and grains

• eat a healthy breakfast

  • may cause body to burn more fat

  • less tendency to overeat due to hunger

• self monitor

  • regularly weigh yourself

  • keep a food jurnal

• physical activity: 1hr/day

fat diet signs

1. promises a quick fix

2. dire warnings of danger from single product or regimen

3. claims that sound too good to be true

4. simplistic conclusions drawn from a complex study

5. recommendations based on a single study

6. dramatic statements refuted by reputable scientific organizations

7. list of “good” and “bad” foods

8. recommendations made to help sell a product

9. recommendations based on studies without peer review

10. recommendations that ignore differences among individuals or groups

lorcaserin (Belviq)

• acts on a specific type of serotonin receptor in the hypothalamus

• thought to activate satiety pathways

• weight loss in clinical trials was modest (half lost 5% body weight)

• controlled substance because very high doses can cause hallucinations

orlistat

• MECHANISM: inhibits lipase » lowers fat digestion

• BENFITS: 65% of participants lose 5% of weight; placebo 50%

• SIDE EFFECTS: GI issues, steatorrhea

GLP -1

• treatment for T2 diabetes

• semaglutide (Ozempic, Wegovy)

• Tirzepatide (Mounjaro, Zepbound)

• produce 20% weight loss

• nausea, vomiting, diarrhea are common

• can cause hypoglycemia

• warning about thyroid cancer

gastroplasty

• can be very effective 75% of patients lose 50% of body weight

• requires significant lifestyle changes

• carries risks of major surgery

anorexia nervosa

• restriction of energy intake to create low body weight

• fear of gaining weight and persistent behaviors that interfere with gaining weight

• disturbance in a person’s weight or shape, lack of recognition of risks of low body weight

bulimia nervosa

• recurrent episodes of binge eating with purging following

• lack of control over an eating episode

• recurrent compensatory behavior to prevent weight gain