Body Composition and Nutritional Assessment
Bioimpedance Analysis
Bioimpedance is used to evaluate the amount of body fat. It is based on the principle that, compared to adipose tissue, lean body mass has higher electrical conductivity and lower impedance with respect to water.
Physical Signs of Nutritional Deficiencies
- Hair:
- Alopecia: Essential fatty acid deficiency.
- Brittle hair, depigmentation: Protein deficiency.
- Lips: Red, swollen, cracked, and ulcerations (cheilosis). Advanced stages can lead to lip retraction. The main cause is riboflavin deficiency.
- Gums: Spongy, bleeding gums indicate vitamin C deficiency.
- Eyes:
- Photophobia, redness of the conjunctiva with corneal circulation: Associated with riboflavin deficiency.
- Xerophthalmia: Vitamin A deficiency.
- Pale conjunctiva: Anemia.
- Skin:
- Dryness, peeling, and pigmentation: Niacin, riboflavin, and biotin deficiency.
- Perifollicular hyperkeratosis: Vitamin A deficiency.
- Dermatitis: Niacin deficiency.
- Edema: Protein deficiency.
- Pale skin: Anemia.
- Transverse grooves and depressed areas: Protein deficiency.
- Concave (spoon-shaped) nails: Iron deficiency.
- Liver: Hepatomegaly (fat infiltration) in protein malnutrition.
- Thyroid: Goiter indicates iodine deficiency.
- Skeleton:
- Cranial deformation and softening of the dome, hypertrophy of the costochondral joints, and deformities of the legs with lateral curvature of the bones: Vitamin D deficiency.
Laboratory Tests for Nutritional Assessment
Skeletal Muscle Mass
Creatinine is formed from creatine, a compound found almost exclusively in muscle. Its excretion rate is related to muscle mass. Skeletal muscle mass (kg) = 4.1 + 18.9 x urinary creatinine excretion in 24 hours (g/day).
Visceral Protein Indicators
Albumin and other plasma proteins are synthesized in the liver and provide a functional index of the body’s protein status. Normal: 3.5 – 5.2 g/dL in adults. May be altered in relation to electrolyte imbalance, liver failure, and sepsis.
Malnutrition
Malnutrition is a syndrome characterized by deterioration of body composition resulting from a negative energy and/or protein balance. These changes are associated with physiological, biochemical, and immune alterations, leading to an increased risk of morbidity and mortality.
- Calorie Malnutrition: Prolonged evolution, predominantly caused by an energy deficit. It is called Marasmus.
- Protein Malnutrition or cachexia: Develops rapidly, is secondary to hypermetabolism and hypercatabolism. It is called Kwashiorkor or hypoalbuminemia.
Preliminary Basic Concepts of Energy
Energy: Typically, energy is defined as the ability to carry out work.
Work: The application of a force through a distance (Force x distance) is known as work.
Forms of Energy: Energy can be found in the following states: chemical, heat, electrical, mechanical, radiant, and nuclear. The body uses the energy contained in the chemical bonds of food constituents.
Energy is neither created nor destroyed; it changes. This is called the first law of thermodynamics (Energy conservation). The energy that food potentially has and can be freed by biochemical processes is measured in terms of calorie intake.
Units: A calorie is the amount of energy required to raise 1 ml of water 1°C at a temperature of 15°C. 1 kcal = 1000 cal; 1 kcal = 4184 J.