Energy Requirements and Utilization

Discipline concerned with the biochemical and physiological processes by which components of Food (nutrients) are utilized to meet the organisms requirements for:
I. Growth
II. Maintenance and repair of tissues
III. Optimal metabolic function
Provides optimal support of patients with severe or chronic illness
Provides specific disease treatment
Used as an adjunct to other Rx
Disease Prevention

You need access and Ingestion, digestion and absorption and metabolic utilization.

I. Access / Ingestion
Poverty, immobility, disasters, famine, war
Cultural, ethnic, traditional food preference
Poor Dentition, eating disorders, anorexia
II. Digestion / Absorption
Swallowing disorders, esophageal disease
Intestinal Disease - Malabsorption
III. Utilization
Inadequate nutrients for physiologic state
Protein/calorie imbalance, vitamin deficiency

Glucose - from sugars, starches, and complex carbohydrates
Amino Acids - from protein
10 Essential amino acids
Non-essential amino acid Nitrogen
Fatty Acids - from fats
Linoleic (18:2) and -linolenic (18:3)fatty acids are essential

Physics: 1 calorie = heat needed to raise 1 gm water 1 °C

Clinical Nutrition: 1 Calorie = 1 Kcal = 1000 “physics” calories

Measures the heat released upon complete oxidation of food sample

CHO-4, Prot-4, Fat-9, EtOH-7

Fat has the highest content, the EtOH, the Carba and Prot.

Carbs-45%, Fat 35% and Protein 20%

in regards to glucose:

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TEE= Activity Energy Expendature + Thermic Efect of food+ Resting Energy Expendature

The sum of basal metabolic energy expenditure and sedentary activities
Organ contribution: liver 29%, brain 19%, muscle 18%, heart 10%, kidney 7%
REE is proportional to Fat Free Mass, (because fat is metabolically inert)
REE is affected by: age, gender, growth, hormones, smoking, disease, pregnancy

Higher % body fat = less REE

Incr= Growth, Pregnancy, Lactation, Lean body mass.
Decr= Aging and fasting

Trauma, burns, inflammation, fever, sepsis, hyperthyroidism all incr. Hypothermia and hypothyroidism all decr.

Dietary Fat to Body fat = 60 C
Dietary glu to glycogen = 140 C
Dietary Protein to muscle Protein= 480 C
TEE of "average" mixed meal 200

Energy Balance = Calorie Intake - TEE

Intake may be determined Indirectly by:
Dietary recall methods: 3-5 day diet recall, food frequency questionnaires
Food diaries
Intake may be determined Directly by:
Use of prepared, controlled portions
In a research ward (e.g. GCRC)

Double labeled water (2H18O2)
TEE calculated from isotopic clearance
Used in free living subjects, but expensive
Direct Calorimetry (Controlled Environment Chamber)
TEE determined directly as heat production
Accurate, but time consuming and expensive
Indirect Calorimetry (Respiratory Quotient)
TEE calculated from O2 used:CO2 produced
Most clinically useful method; bedside use

Resting Energy Expenditure (REE) can be estimated using a variety of formulas
The Harris Benedict Formula is one of the most commonly used methods

Cal(♀) = 655 + 9.5WKg + 1.9Hcm - 4.7A
Cal(♂) = 66 + 13.8WKg + 5.0Hcm - 6.8A

Example:

REE for a 182 lb, 5’10”, 28 year old male:

66+(13.8*82.6)+(5*178)-(6.8*28) = 1905