Adult Nutrition Lecture 22

Adult Nutrition Lecture 22

• Learning Objectives: Describe and discuss physiological changes in adults, key components determining energy needs and expenditure, methodologies to determine energy needs, and methods to adjust energy needs for weight loss.

Definition of Adult Stages

• Early Adulthood: 20-39 years
• Middle Adulthood: 40s
• "Sandwich" Generation (50s): Often multigenerational caregivers, frequently concerned with diet, physical activity, smoking, and body weight.
• Later Adulthood (65+): This stage is not defined as a specific age range
• Health concerns (diet, physical activity, smoking, body weight) are frequently prevalent

Nutritional Factors Influencing Disease

• Cancer: Low fruit and vegetable intake, low antioxidant intake (especially vitamins A & C), low whole grains and fiber, high dietary fat intake, nitrosamines (burnt/charred food), pickled/fermented food, alcohol.
• Heart Disease: High saturated fat (>10% calories), trans-fatty acid intake, dietary cholesterol (>300 mg), low fruit/vegetable intake, low antioxidants, low whole grains, no or excess alcohol intake, high sodium intake, low potassium, low dairy intake, high waist circumference (men >40 in, women >35 in)
• Obesity: Caloric intake exceeding needs, unstructured eating, frequent fast-food consumption, high fat intake, sugar-sweetened beverages, energy-dense, low-nutrient food choices.
• Diabetes: Atherogenic and obesogenic diets. Obesity (BMI >30) and physical inactivity are also risk factors. Moderate alcohol intake may reduce risk in middle-aged adults (men >45, women >55).

Physiological Changes - Bone Mass

• Bone growth stops in the 20s.
• Bone density continues to increase until 30.
• Bone loss begins around 40.

Physiological Changes - Body Composition

• Positive energy balance leads to increased weight and adiposity.
• Fat redistribution, with central and intra-abdominal fat increasing, while subcutaneous fat decreases.
• Dexterity and flexibility decline with age.

Physiological Changes - Hormones (Women)

• Decline of estrogen (menopause).
• Increased abdominal fat.
• Increased risk of cardiovascular disease and accelerated bone loss.

Physiological Changes - Physical Capacity

• Physical working capacity declines 5-10% per decade in older adults, particularly non-linearly with musculoskeletal disease, obesity, and other conditions affecting capacity.

Physiological Changes - Gut Microbiome

• Gut dysbiosis is a common change in aging, with a shift between microbial components.
• The aging process is characterized by altered microbial composition.

How is Energy Need Determined?

• Basal Metabolic Rate (BMR): Daily energy expenditure for involuntary processes, often measured as REE or RMR. Largely the largest component of energy expenditure.
• Thermic Effect of Food (TEF): Energy expenditure attributed to food metabolism.
• Physical Activity Energy Expenditure (PAEE): Energy expenditure related to exercise thermogenesis and non-exercise activity thermogenesis (NEAT).

Factors Affecting Energy Needs

• Lean body mass
• Health status
• Age
• Gender/body size
• Activity levels
• Hormones
• Individual variation

Determining Energy Needs – Equations

• Mifflin-St. Jeor Equation: A more accurate formula for REE than the Harris-Benedict equation, particularly for overweight and obese adults. Specific equations are provided for males and females. Activity factors for different activity levels are provided.

Determining Energy Needs - Calorimetry

• Direct Calorimetry: Measures heat production in a chamber to determine energy expenditure. Accurate but expensive and confines the subject to the chamber environment.
• Indirect Calorimetry: Calculates heat produced based on gas exchange (O2 and CO2), determining REE (resting energy expenditure), nearly equal to BMR. Relatively inexpensive but depends on metabolic rate being at a steady state and confined to a metabolic cart.
• Doubly Labeled Water: A gold standard for measuring free-living total energy expenditure. Involves giving subjects "tagged" water, and collecting excretion of isotopes in saliva and urine. Expensive.

Adjusting Energy For Weight Change

• Weight loss composition is not all fat.
• Calorie restriction and exercise affect fat mass and fat-free mass composition differently.
• Greater adiposity = larger expected weight loss for the same change in energy intake.

Is There a Set Calorie Restriction Rule for Weight Loss?

• 3500 kcal/week for 1 lb weight loss is an often cited rule of thumb but is unrealistic.
• Weight loss occurs more gradually than assumed and is influenced by physiological variations over time.

Mathematical Simulation Models For Weight Change

• The body needs time to adjust to changes.
• Mathematical models account for the dynamic nature of weight change.
• Factors such as initial weight, weight composition, and metabolic adaptations are considered to provide more accurate estimations for calorie requirements.

Acceptable Macronutrient Distribution Ranges

• Fat: 20-35% of calories
• ** Carbohydrate:** 45-65% of calories
• ** Protein:** 10-35% of calories
• Specific recommendations (in kcal and grams) for a 2000 kcal daily diet are provided.

Summary

• With aging, physiological variables decline.
• Energy expenditure is the sum of BMR, TEF, and physical activity.
• Several methods exist to estimate energy expenditure.
• Energy needs must be adjusted if planning weight loss.
• Mathematical models offer more effective estimations of calorie requirements accounting for dynamic weight loss.