Week 11: Energy Needs - Body Composition and Weight

body composition

• amount of fat tissue to lean mass

• usually expressed as percent

• some fat absolutely necessary for health

lean mass

muscle, bone, organs

subcutaneous fat

adipose tissue located under the skin

visceral fat

adipose tissue stored around the organs and in the abdominal area

• insulates body from cold temperatures

• protects and cushions internal organs

brown fat

adipose tissue with function to generate heat

central (android) obesity

• more visceral fat in the abdomen

• associated with increased risk for heart disease, hypertension, diabetes, increased LDL, decreased HDL

• visceral fat release fatty acids that travel to tissues → insulin resistance

gynoid obesity

• fat distribution more around thighs and buttocks

• more common in F than M

tools for assessing body composition (DIRECT)

1. hydrostatic weighing

2. bod pod (air displacement)

3. DEXA (dual-energy X-ray absorptiometry)

4. BIA (bioelectrical impedance analysis)

hydrostatic weighing

• assess body volume via underwater weighing

• accurate tool with 2-3% margin of error

air displacement (Bod Pod)

• measures air displacement rather than water displacement

• accurate within 3%

DEXA (duel-energy X-ray absorptiometry)

MOST ACCURATE MEASURE: 1-2% margin of error

• uses low-energy X-ray beams to measure bone density and body mass

BIA (bioelectrical impedance analysis)

• measures resistance to low-energy current

• current travels through body fat and muscle

• influenced by hydration status

• not as accurate as body density tests

INDIRECT assessments

1. weight circumference 

2. BMI (body mass index)

weight circumference

• quick indicator of health risk

• indication of fat location, not % body fat

• increased health risk with normal BMI if >35 inches in women, >40 inches in men

body mass index (BMI)

• calculates body weight in relation to height

• population-level measure of adiposity

• potential screening tool on an individual level

• NOT a direct measure of body fat %

• not accurate for everyone

underweight BMI

<18.5

normal weight BMI

18.5-24.9

overweight BMI

25.0-29.0

obesity BMI

30 or higher

class 1 obesity BMI

30.0-34.9

class 2 obesity

35.0-39.9

class 3 (severe) obesity

40.0+

underweight health risks

• symptomatic of malnutrition/disease

• higher risk of anemia, osteoporosis/bone fractures, heart irregularities, amenorrhea

• correlated with poor mental health, inability to fight infection, trouble regulating body temp, decreased muscle strength, risk of premature death

• may be unintentional due to disease-induced malabsorption or certain medications and smoking

excess adiposity health risks

• increased risk of heart disease, hypertension, stroke, gallstones, hyperlipidemia, sleep apnea, reproductive problems, risk of certain cancers

• metabolic syndrome associated with central adiposity

appetite

desire to eat food with/without the presence of hunger 

• includes cravings, reactions to cues like sight and smell

hunger

sensation indicating physiological need for food

satiety

sensation of fullness after eating

leptin

stimulates satiety

• produced by adipocytes

ghrelin

stimulates hunder

• produced by stomach

• levels higher during fasting windows (ie; between meals, during sleep)

GLP-1

hormone stimulating satiety; released by gut after eating

• produced by small intestine

• decreases glucagon secretion

• supports insulin secretion

• slows gastric emptying

• inhibits food intake by promoting satiety

stimulate satiety

insulin, leptin, peptide YY, cholecystokinin (CKK), GLP-1

stimulate hunger

ghrelin, neuropeptide Y

processes regulating satiety

1. physiological cues prompt release of hormones → stomach distension (stretch receptors triggered) → detecting entrance of macronutrients into SI → hormones communicate signal for satiety to hypothalamus

2. leptin quantity influenced by quantity of fat stores (inhibits neuropeptie Y)

3. ghrelin stimulates neuropeptide Y’s impact on hypothalamus

hypertrophy

fat cells grow in size; number of fat cells does not decrease but individual cells can shrink

hyperplasia

cell devision to increase number of fat cells

hormones involved in adipocyte fat storage

lipoprotein lipase, hormone-sensitive lipase

non-modifiable factors impacting BMR

age genes, sex (F tend to have higher proportions of fat mass), hormones (thyroid hormones, menstrual cycles)

modifiable factors impacting BMR

lean body mass (more metabolically active), body size, stress, fasting and starvation (48 hours +), drugs (including caffeine and nicotine)

obesity trends over time

• increasing globally → 3x increase in 30 years

• 30-40% of Americans in obese BMI range

theories of weight change and obesity

• energy balance (calories in, calories out)

• set-point theory (body defends a set body weight)

• carbohydrate-insulin model

energy balance theory

• energy out: basal metabolism, thermic effect of food, thermic effect of exercise

• energy IN: protein, carbohydrate, fat, alcohol found in foods and beverages

set point theory

rooted in homeostasis: body thought to have predetermined weight or fat-mass range

• maintained by physiological mechanisms that resist deviation and maintain set point

• possible explanation of why weight is regained

physiological mechanisms that resist deviation and maintain set point

• ghrelin increases when on low kcal diet (people feel hungrier)

• weight loss → increased appetite, reduced metabolism (adipocytes shrink, leptin drops)

• weight gain triggers weaker mechanisms

• asymmetrical defense favors weight gain

life events/stages that change set point

• childbirth

• menopause

• aging

• disease

carbohydrate-insulin model

• higher intake of CHO raises BG levels → pancreas responds by increasing insulin secretion

• insulin drives uptake of glucose by cells → glucose either used or stored

  • primarily driven by high glycemic index/high refined CHO intake

glycogenesis

glucose storage in liver and muscle

glycolysis

use of glucose for ATP

lipogenesis

glucose converted to triglycerides for storage

associated with improved health outcomes

5-10% of body weight loss

weight loss challenges

• not difficult to achieve initially, but people can be disappointed with small % of total body weight lost (due to body/self image)

• difficult to maintain

• diet changes difficult to sustain

• people feel frustrated/ashamed with challenges → healthcare avoidance

weight loss medications

1. GLP-1 receptor agonists: ozempic, victoza, trulicity, etc

2. GLP-1/GIP receptor agonists: mounjaro 

bariatric surgery

• stomach is closed off → small pouch left that can hold ¼ cup of food at a time

• post-surgery intake limited

• requires supplementation of iron, vitamin B12, calcium, vitamin C

principles of healthy eating

1. adequacy

2. balance

3. variety

4. moderation

5. nourishment and enjoyment

social determinants of health

1. access to healthcare

2. education

3. economic stability

4. social community and context

5. neighborhood and built environment

allostasis

ability to achieve stability through change

allostatic load

• cumulative health costs of exposure to stressors

• sustained or fluctuating

• physiological impact: neural, endocrine

• impact of resulting behaviors (circadian rhythms, sleep disruption, lack of exercise, etc)

social ecological model

• public policy, community, organizational, interpersonal, individual

• systems-level considerations (levels’ interactions, too)

  • changes over time

• influences on health behavior

• good to combine with social determinants of health

life course models

interactions of exposure

1. critical periods (exposure → disease; latency)

2. accumulation models

3. chains of risk (exposure influences disease and future exposures)

iron-deficiency anemia

• most common type of anemia; may be asymptomatic

• Sx = fatigue, pale skin, cold hands and feet, dizziness

• diagnosis via monitoring blood levels (CBC = complete blood cell count) → hemoglobin, hematocrit, mean corpuscular volume → iron panel (serum Fe, ferritin, transferrin)

macrocytic anemias

• can be caused by vitB12 or folate deficiency (adequate B12 needed to activate folate for RBC division)

• slowed DNA synthesis

pernicious anemia

macrocytic anemia caused by vitamin B12 deficiency

• reduced B12 absorption → B12 deficiency → megaloblastic anemia 

• secondary to intrinsic factor deficiency (IF needed to bind B12)

• Sx = fatigue, weight loss, anorexia, neurological symptoms (confusion, concentration and cognitive decline)

osteoporosis

disease characterized by low bone mineral density

• increased risk of fractures

• common among older adults, but peak BMD achieved in young adulthood

• exercise and diet through lifecourse matter for prevention

• screening via DEXA scan

osteopenia

lower BMD but not reaching osteoporosis diagnostic criteria

eating disorders

definitions come from DSM5; criteria and definitions will continue over time

anorexia nervosa diagnostic criteria

restriction of energy intake relative to requirements → significant low body weight in CONTEXT of age, sex, developmental trajectory, physical health

• intense fear of gaining weight/becoming fat

• persistent behaviors interfering with weight gain

• disturbed by body weight/shape → self-worth influenced by body weight/shape 

• persistent lack of recognition of seriousness of current low body weight

• restricting or binge-eating/purging type

bulimia nervosa diagnostic criteria

characterized by purging (recurrent inappropriate compensatory behavior to prevent weight gain ie; laxatives, diuretics, self-induced vomiting)

• recurrent episodes of binge eating

• binge eating and compensatory behaviors both occur at least 1x/week for 3 months (on average)

• self-evaluation unduly influenced by body shape and weight

• disturbance does not occur exclusively during episodes of AN

binge eating disorder diagnostic criteria

• recurrent episodes of binge eating with loss of control

• marked distress regarding binge eating

• binge eating occurs at least 1 day/week for 3 months

• not associated with regular use of inappropriate compensatory behavior

• does not occur exclusively in setting of AN or BN

OSFED (other specified feeding or eating disorders)

• atypical AN, BN/BED of low frequency/duration, purging disorder, night eating syndrome

consequences of malnutrition

bradycardia, hormonal disruptions, nutrient deficiencies, psychological impairment, low quality of life

atypical anorexia nervosa

• all criteria for AN met EXCEPT weight is within/above normal range

• often present for treatment after longer duration, may not have access to higher levels of care

• physiologic complications of malnutrition/starvation can be/are just as serious

biopsychosocial model

1. social risk factors

2. psychological risk factors

3. biological risk factors

social risk factors for ED development

• thin ideal

• family dynamics and food modeling

• culture, comments

psychological risk factors for ED development

• mental health and coping skills

• trauma

• comorbid disorders

• traits (ie; perfectionism)

biological risk factors for ED development

• genetics

• microbiome

first nutrition principles

1. adequate, consistent meals (not starting with caloric deficit, avoid meal skipping, incorporate snacks, identify/shift from “overly virtuous” patterns)

2. balance of macronutrients

3. variety (education and strategies to interrupt black and white thinking)

4. “moderation” (learning portions, permission, and feedback; introduction of challenging foods)

5. enjoyment