Adult Nutrition Lecture 22 PDF

ADULT NUTRITION LECTURE 22 Learning Objectives  Describe and discuss the physiological changes in this age group.  Discuss key components that determine energy needs and expenditure.  List and discuss methodologies to determine energy needs.  Discuss methods to adjust energy needs for w...

ADULT NUTRITION LECTURE 22 Learning Objectives  Describe and discuss the physiological changes in this age group.  Discuss key components that determine energy needs and expenditure.  List and discuss methodologies to determine energy needs.  Discuss methods to adjust energy needs for weight loss Definition of this stage  Early adulthood = 20-39 yrs  Middle adulthood = 40s  “Sandwich” generation = the 50’s - Many are multigenerational caregivers - Health concerns are frequently added Diet, Physical activity, Smoking, Body weight  Later adulthood—age 65+ Nutritional Factors that Influence Disease Physiological Changes – Bone mass  Growing stops by the 20’s  Bone density continues until 30  Bone loss begins around 40  Physiological Changes- Body Composition  Positive energy balance  ↑ weight and adiposity  ↓ muscle mass  Fat redistribution- ↑ central & intra-abdominal space, ↓ subcutaneous fat ↓ Dexterity and flexibility decline 100 Muscle Area (mm 1010090 0 2) Muscle size (cm2) 90980 0 80870 0 70760 0 60650 0 50540 0 40430 0 3030 220 020 0 1010 202030304040 50506060 7070 80809090 00 10 20 30 40 50 60 70 80 90 Age(years) (years) Age Age (years) Physiological Changes - Hormones Women  Decline of estrogen  menopause  Increase in abdominal fat  Increase in risk of cardiovascular disease & accelerated loss of bone mass Men  Gradual decline in testosterone level & muscle mass Physiological Changes- Physical capacity Physical working capacity declines 5-10% per decade in older adults - Nonlinear - Declines accelerated with musculoskeletal disease, obesity and other conditions Fleg J L et al. Circulation 2005 Physiological Changes- Gut Microbiome Gut Dysbiosis  How is Energy Need Determined? Based on Energy Expenditure 1) Basal metabolic rate - Daily BMR expenditure-involuntary processes - Often measure as REE or RMR, used interchangeably - Largest part of energy expenditure 2) Thermic effect of food (TEF) - Metabolism of food 3) Physical activity energy expenditure - Exercise thermogenesis - Non-exercise activity thermogenesis (NEAT) What Factors Impact Energy Needs?  Lean body mass  Health status  Age  Gender/body size  Activity levels  Hormones  Individual variation  Determining Energy Needs Estimate with equations- Mifflin-St. Jeor Energy Estimation Formula Validated and more accurate than old Harris-Benedict equation for overweight and obese adults Males: REE = (10 x wt in kg) + (6.25 x ht in cm) – (5 x age) + 5 Females: REE = (10 x wt in kg) + (6.25 x ht in cm) – (5 x age) – 161 Multiply by appropriate activity factor Determining Energy Needs Calorimetry Derived from the Latin word calor, meaning heat and the Greek word μέτρον (metron), meaning measure Calorie : amount of energy needed to raise the temp of 1kg of water by 1 degree c Measure or estimate heat production to determine energy expenditure, and thus, energy needs Determining Energy Needs- Direct Calorimetry  Measurement of heat production in chamber  Heat generated by body transferred to air and walls  Record temperature change in the air and water Strengths: Accurate Limitations: Expensive to build/maintain Confined to chamber Determining Energy Needs- Indirect Calorimetry Calculates heat produced based on gas exchange Amount of O2 and CO2 exchanged in lungs normally equals that used and released by body tissues Glucose and fat metabolism depend on O2 availability and produce CO2  Determine REE (Resting Energy Expenditure) which is nearly = to BMR Strengths: relatively inexpensive and easy to measure Limitations : based on assumption of steady-state confined to metabolic cart Determining Energy Needs- Doubly Labeled Water  Gold standard for measuring “free-living” total energy expenditure  Subjects are given a dose of “tagged” water - Hydrogen and oxygen labeled with a stable isotope - Water labeled with elements deuterium and oxygen-18 (D2 18O)  Excretion of isotopes in saliva and urine is used to calculate average energy utilization over several days Limitations: expensive How do you Adjust Energy for Weight Change? Composition of weight lost – not all fat Fat mass Fat-free mass Calorie restriction 75% 25% CR + exercise 88% 12% Is the weight loss going to be same for normal weight and obese ? Greater adiposity = larger expected weight loss for the same change of energy intake Is there a set calorie restriction rule for weight loss? Standard rule = -3500 kcal/week for 1 lb weight loss energy in = energy out? Not as simple!! Dynamic changes – not static ↓ body weight = ↓ REE and energy requirements Dynamic mathematical models of human energy regulation and weight change developed Takes into account: Composition of weight lost, initial weight/adiposity Metabolic adaptations/Changes in energy needs (REE) 1 yr 100 kg man -480 kcal/d Predicted weight change using dynamic modeling 15 vs 25 kg X ‘rule’ at 1y NIDDK -480 kcal/d Body weight simulator http://bwsimulator.niddk.nih.gov Time (years) Hall KD et al. Lancet. 2011 NIDDK weight simulator: -26 lb in 6 months How many calorie intake per day with -500 kcal/d rule? Dynamic mathematical models of human energy regulation and weight change  Challenges traditional dogma  Energy balance is complex – dynamic Take home: - 3500 rule = unrealistic expectation - Undermine people’s efforts to lose weight - Weight loss occurs more gradually than thought -10 kcal/d  loss of 1 pound over 3 years -250 kcal/d  loss of 25 lb but will take 3 years for most overweight or obese adults to get 95% of the way Half of weight will be lost in first year, weight loss slows thereafter It takes time for new findings to be accepted by health organizations and practitioners Nutrient Recommendations Acceptable Macronutrient Distribution Ranges Fat 20-35% of calories Carbohydrate 45-65% of calories Protein 10-35% of calories 2000 kcal/d Fat: 400-700 kcal (44-78 g) Carbohydrate: 900-1300 kcal (225-325 g) Protein: 200-700 kcal (50-175 g) Summary  With aging the physiological variables start declining  Energy expenditure is composed of there major components - BMR, TEF, and physical activity  There are multiple methods to estimate energy expenditure (to calculate energy requirement)  Energy needs will need to adjusted if planning weight loss  Mathematical simulation models take into account the dynamic nature of weight loss, and can be used to estimate calorie requirement