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DEPARTMENTS: NUTRITION Q&A

Obesity and Wound Healing

Collins, Nancy PhD, RD, LD/N

Author Information

Q: I understand that a patient with a wound requires additional calories and protein for healing. Is this true for an overweight patient as well?

A: What a patient weighs on a scale does not adequately represent his or her health or ability to heal a wound. Several nutritional issues must be assessed to prescribe an appropriate dietary regimen for an overweight patient with a wound.

Defining Obesity

A patient is considered obese if he or she weighs more than 120% of his or her desirable body weight. 1 The Hamwi formula is often used by professionals to calculate ideal body weight (IBW) (Table 1). IBW, however, has limited clinical utility and simply provides a starting point for nutrition assessment. Obtaining a patient’s usual body weight (UBW), which depends on patient recall, or a patient’s adjusted body weight (AdjBW) can be more clinically useful (Table 2). AdjBW provides a more realistic picture of an overweight patient and should be used for nutritional assessment rather than IBW when a client is obese. 2

Table 1
Table 1:
HAMWI FORMULA
Table 2
Table 2:
ADJUSTED BODY WEIGHT FORMULAS

Over the past several years, the concept of IBW has slowly been replaced by body mass index (BMI). 3 BMI assesses body weight relative to height and classifies the result as underweight, healthy, or progressively worsening levels of obesity (Table 3). Obtaining a patient’s BMI has come to the forefront as an assessment parameter because it brings the concept of body composition to nutritional assessment. Clinical judgment must still be used because BMI may not be a reliable indicator of body composition for patients with edema, muscular patients, or very short or very tall patients.

Table 3
Table 3:
BODY MASS INDEX

Body Composition

Body composition is the amount of lean tissue compared with fat. When there is an imbalance between caloric intake and energy expenditure, the excess is stored as fat. Overweight and obese patients weigh more due to this excess fat storage.

Typically, body composition analysis consists of determining values for 3 body compartments plus water: (1) the fat mass, or energy storage compartment; (2) the extracellular mass, or support compartment; and (3) the body cell mass, or functional compartment. The fat mass is metabolically inactive and acts as a reserve if caloric intake drops, as in cases of starvation. The extracellular mass consists of extracellular fluids and solids, such as bone and cartilage. It is metabolically inactive and has the primary function of support and transport. 4 The body cell mass is where the functions of the body occur, such as oxygen consumption, carbon dioxide production, glucose oxidation, protein synthesis, and other metabolic work. It is the total mass of all the cellular elements in the body and, therefore, represents the metabolically active component of the body. 4 Although technically different, the term body cell mass is often used interchangeably with lean body mass.

The most convenient and cost-effective way to measure the 3 body compartments is through bioelectrical impedance analysis (BIA), a quick, painless procedure that sends a low electrical current through the body. The current is used to obtain electrical and resistance measurements that are fed into mathematical equations calculated by a computer. The technique is based on the principle that lean tissue has a higher electrical conductivity and a lower impedance rate than fat. The results are affected by hydration status so, ideally, the subject should be fully hydrated to obtain the most accurate results. BIA is not routinely performed in wound care centers. However, as the importance of maintaining proper body composition becomes more closely implicated with good wound healing, this type of analysis may become more readily available.

Hypermetabolism and Catabolism

Wound healing depends on adequate protein intake and protein stores because protein is needed at every step of the healing process. 5 Protein stores may be eroded due to the increased demand of the wound healing process. Many patients with wounds are hypermetabolic due to the body working harder and faster to regain homeostasis and heal. This may lead to a catabolic state whereby the body breaks down lean tissue to quickly release fuel and keep up with demand. Therefore, it is possible for an overweight or obese patient to have depleted his or her lean body mass and protein stores while maintaining a considerable amount of extra fat mass. Herein lies the problem with relying on scale weight to determine the nutritional requirements for an overweight patient. The total weight is irrelevant; the weight of the body’s functional compartment is what is crucial.

Laboratory Data

Biochemical data provide a readily available tool to evaluate the protein stores of a patient with a wound. Albumin and prealbumin levels should be drawn to determine a patient’s visceral protein status. Because prealbumin has a short half-life of approximately 2 days, this test may be performed weekly to track protein status. 6 In addition, serial measurements are necessary to ascertain that protein is not being catabolized for fuel. Ideally, the diet prescription for a patient with a wound consists of adequate protein to maintain a positive nitrogen balance and is monitored by the measurement of serial prealbumin levels.

Caloric Needs

A patient with a wound must be provided with adequate calories and protein in order to promote wound healing. Caloric needs are typically determined using the Harris-Benedict equation or by estimating calories per kilogram of body weight. However, these types of estimates may not be accurate for obese patients; results can vary greatly, depending on whether a clinician uses a patient’s IBW, UBW, actual body weight, or AdjBW as the basis for the formula. AdjBW is thought to be an estimate of lean body mass, although there are no large-scale studies to validate this in the obese population. 7 Until further information becomes available, however, it is recommended to use AdjBW in the Harris-Benedict equation.

The ideal way to determine caloric needs is by indirect calorimetry, which can be measured by a metabolic cart, a bedside monitor (S5 Critical Care Monitor; Datex-Ohmeda, Tewksbury, MA), or a portable, handheld indirect calorimeter that measures oxygen consumption and determines resting metabolic rate (MedGem; Healthetech, Golden, CO). 8 Information obtained from indirect calorimetry can be used to determine the necessary calories, without underfeeding or overfeeding the patient. The patient should be weighed weekly and lose only approximately 1 pound per week.

A good way to provide additional protein without adding extra calories is by using a protein powder. Protein powders may be mixed with a beverage or other food to raise the protein content of the patient’s diet without serving extra food.

In addition, many overweight patients have diabetes, making it important to monitor and control blood glucose levels. Elevated blood glucose levels can be an impediment to wound healing.

Recommendations

Obesity is a long-term medical problem and treatment requires patient motivation and behavioral changes. When a patient is being treated for a wound, the types of changes necessary to treat obesity are usually not a top priority. It is prudent to heal the wound first, then address the patient’s weight.

Baseline albumin and prealbumin levels should be obtained at periodic intervals to monitor protein status. If body composition analysis is available, it should be utilized and evaluated in conjunction with laboratory data. For difficult cases, obtain referral for or consultation with a registered dietitian.

References

1. Mahan LK, Escott-Stump S. Krause’s Food, Nutrition & Diet Therapy. 10th ed. Philadelphia, PA: WB Saunders Company; 2000. p 486.
2. Florida Dietetic Association. Handbook of Medical Nutrition Therapy: The Florida Diet Manual. 2000 ed. Tallahassee, FL: Florida Dietetic Association; 2000. p I1.5.
3. St. Jeor ST, Brownell KD, Atkinson RL. New Multidisciplinary Strategies in Obesity Management. Monograph. Health Learning Systems. 1997.
4. RJLSystems. Why is body composition important? [on-line] Available at http://www.rjlsystems.com/research/bcimportance.html. Accessed July 29, 2002.
5. Demling RH, Stasik L, Zagoren AJ. Protein-energy malnutrition and wounds: nutritional intervention. Treatment of Chronic Wounds Number 10. Hauppauge, NY: Curative Health Services; 2000.
6. Collins N. The difference between albumin and prealbumin. Adv Skin Wound Care 2001; 5:235–6.
7. Trombley LE, Reinhard T, Klurfield D. Energy expenditure in the critically ill obese patient. Support Line 2001; 2:18–24.
8. Healthetech. MedGem product literature. Golden, CO; 2002. Available at: http://www.healthetech.com. Accessed July 29, 2002.

SUMMARY OF RECOMMENDATIONS

  • Provide adequate calories and protein to halt catabolism.
  • Recognize that scale weight reflects increased fat stores and not lean body mass.
  • Analyze and monitor body composition, if possible.
  • Estimate caloric needs using a handheld calorimeter, if possible.
  • Determine caloric needs; if calorimetry is not possible, use adjusted body weight in Harris-Benedict equation.
  • Determine baseline protein status with albumin and prealbumin levels.
  • Monitor protein status using serial prealbumin levels weekly or bimonthly; adjust protein intake accordingly.
  • Consider a nitrogen balance study if prealbumin levels do not improve. This requires careful collection of a 24-hour urine sample and a complete dietary intake record for the corresponding 24-hour period.
  • Provide additional protein with protein powders.
  • Weigh patient weekly to ensure no more than approximately 1 pound of weight is lost per week; adjust caloric intake accordingly.
  • Monitor blood glucose and provide reduced-carbohydrate diet and sugar-free supplements, if necessary.
  • Consult a registered dietitian.
  • Refer patient for long-term weight loss plan after critical illness has been treated and resolved.
© 2003 Lippincott Williams & Wilkins, Inc.