Body Composition and Surgical of Obesity
Treatment
Effects of Weight Loss on Fluid Distribution
MANOLO MAZARIEGOS, M.D.,*t JOHN G. KRAL, M.D., PH.D.,t JACK WANG, M.S.,4 MASAKO WAKI, M.D.,4 STEVEN B. HEYMSFIELD, M.D.,4 RICHARD N. PIERSON, JR., M.D.,4 JOHN C. THORNTON, PH.D.,4 and SEIICHI YASUMURA, PH.D.§
Obesity is associated with absolute and relative expansion of the extracellular water compartment (ECW). The effects of substantial and prolonged weight reduction on body water distribution are unknown, however. The authors studied total body water (TBW) by tritiated water dilution, ECW by 35S04 dilution, exchangeable sodium (Nae) by 24Na, and total body potassium (TBK) by 4'K whole-body counting in 25 severely obese women (body mass index IBMIJ = 48 ± 7 kg . m-2, mean ± standard deviation) aged 36 ±8 years before and at intervals after gastric restrictive (GR; n = 12) and malabsorptive (MA; n = 13) operations for obesity. Results are compared with a control group of 26 healthy normal-weight women (BMI = 21 ± 2). Before operation, the obese patients had absolute elevations of all water compartments compared with controls, with significantly higher ratios of Nae to TBK (1.17 ± 0.13 versus 0.91 ± 0.10; p < 0.05) and ECW to intracellular water (ICW) (E/I = 0.82 ± 0.17 versus 0.63 ± 0.06; p < 0.05). After weight loss of 52 ± 20 kg in MA and 47 ± 19 kg in GR patients (nonsignificant between groups) to a stable level 22 ± 8 months after operation, there were statistically significant reductions in TBW, ICW, TBK, and Nae in both groups, but a significant reduction in ECW only after GR. Adjusting for preoperative weight, duration of follow-up, and rate of weight loss, E/I was greater after MA than GR (1.09 ± 0.25 versus 0.82 ± 0.14; p < 0.05). The elevated preoperative E/I ratio did not normalize with weight loss after surgery, and the response was related to the type of operation. The finding remains to be explained although the increased E/I after MA may reflect mild protein-calorie malnutrition not detectable in the blood. The persistence of elevated E/I with significant weight loss after GR might imply an intrinsic or irreversible imbalance of fluid distribution in obese patients. OB
From the Department of Surgery,t SUNY HSC Brooklyn, Body Composition Unit,f St. Luke's-Roosevelt Hospital Center, Columbia University, New York; and the Department of Physiology,§ SUNY HSC Brooklyn, New York
part to the high ratio of extracellular to intracellular water content (ICW) of adipose tissue found in obesity.2'3 The cause and possible physiologic significance of this finding is unknown. Although relative increases in ECW are commonly attributed to protein-calorie malnutrition,4'5 with edema and inability to retain crystalloid fluid in the intravascular space, this is an unlikely cause in untreated obesity. Studies of effects of therapeutic weight loss on the increased ECW in obesity might demonstrate whether this increase is reversible. Surgical treatment of obesity offers an opportunity to study changes in body composition associated with large and sustained weight loss, with a view to determining reversibility of the abnormal fluid distribution in obesity. Earlier studies with various techniques of the effects on body composition of two physiologically different operations: gastric restrictive (e.g., vertical banded gastroplasty6) and malabsorptive (e.g., jejunoileal bypass7) yielded equivocal results.8'6 Such studies rarely measured extracellular water directly, instead relying on assumptions about hydration of the lean body that have not been validated in obese patients.' Here for the first time, we present studies using independent, direct methods to determine ECW before and after gastroplasty and intestinal bypass in severely obese patients.
ESITY IS ACCOMPANIED by a variety of changes
in body composition. In addition to the obvious
increase in adipose tissue mass, there is a relative expansion of extracellular water (ECW),' which is due in
Methods
Address reprint requests to John G. Kral, M.D., Ph.D., Department of Surgery, Box 40, SUNY HSC at Brooklyn, 450 Clarkson Avenue, Brooklyn, NY 11203. Accepted for publication November 25, 1991. * Current address: Gerontology Group, Center for Studies of Sensory Impairments, Aging and Metabolism, Guatemala.
Subjects
Twenty-five obese women (aged 36 ± 8 years, mean ± standard deviation) were studied at baseline before anti-
69
Ann. Surg. . July 1992
MAZARIEGOS AND OTHERS
70
obesity surgery (Table 1) and at postoperative intervals. None of the patients had clinically significant heart failure or respiratory disease. Patients with diabetes, hypertension, or renal or hepatic disease were excluded. Patients had no history of malignancy or ofprior surgical treatment of obesity. They did not regularly take any medication known to affect body composition or nutritional state. A nonobese control group consisted of 26 healthy women matched for height and age (age, 38 ± 13 years).
measured in a 4-pi whole-body 40K counter, with an attenuation correction applied according to body weight.'8 Exchangeable sodium was measured from blood samples approximately 18 hours after oral administration of 24Na. Intracellular water (ICW) was obtained by subtracting ECW from TBW. The relative fluid distribution was expressed as the ECW/ICW ratio (E/I). Intracellular potassium, Ki, was calculated in mEq/L from: TBK - serum potassium X ECW/ICW.
Blood Chemistry Routine serum analyses were made of electrolytes, including magnesium and calcium, albumin, globulin, total protein, iron, and iron-binding capacity.
Surgical Procedures
Body Composition Tests Tests were made in the morning after overnight fasting. Height was measured to ±5 mm and weight to ±0.1 kg in patients wearing a hospital gown without shoes. Total body water (TBW), extracellular water (ECW), total body potassium (TBK), and exchangeable sodium (Nae) were measured before the weight-reduction surgery and periodically at 6- to 12-month intervals after surgery. All subjects gave written consent, approved by the institutional review board. The methods included in this protocol have been described in detail elsewhere.'7",8 Total body water was determined from the 3-hour dilution of 200 uCi tritium (3H20), with a precision of ± 1.2%. Extracellular water was measured as the volume distribution of 50 ACi Na235SO4 by zero-time extrapolation from samples at 120, 140, 160, and 180 minutes.'7 Total body potassium was TABLE 1. Body Composition in 25 Obese Women and 26 Nonobese Control Women
Group
Age (yr) Height (cm) Weight (kg) BMI (kg/mr2) TBW (L) ECW (L) ICW (L) TBK (mEq) Nae (mEq)
E/I Nae/TBK TBK/TBW
Obese
Control
p
36.5 ± 8.3 162.3 ± 6.0 127.0 ± 18.8 48.8 ± 6.8 44.7 ± 6.7 19.9 ± 3.8 24.8 ± 4.2 3096 ± 508 (24) 3455 ± 422 (20) 0.82 ± 0.17 1.17 ±0.13(18)
37.9 ± 13 164 ± 7 56.6 ± 4.6 21 ± 2 31.4 ± 2.8 12.1 ± 1.0 19.3 ± 2.1 2568 ± 257 (25) 2334 ± 243 0.63 ± 0.06 0.91 ±0.10(25) 82 ± 6 (25)
NS NS
Treatment
Effects of Weight Loss on Fluid Distribution
MANOLO MAZARIEGOS, M.D.,*t JOHN G. KRAL, M.D., PH.D.,t JACK WANG, M.S.,4 MASAKO WAKI, M.D.,4 STEVEN B. HEYMSFIELD, M.D.,4 RICHARD N. PIERSON, JR., M.D.,4 JOHN C. THORNTON, PH.D.,4 and SEIICHI YASUMURA, PH.D.§
Obesity is associated with absolute and relative expansion of the extracellular water compartment (ECW). The effects of substantial and prolonged weight reduction on body water distribution are unknown, however. The authors studied total body water (TBW) by tritiated water dilution, ECW by 35S04 dilution, exchangeable sodium (Nae) by 24Na, and total body potassium (TBK) by 4'K whole-body counting in 25 severely obese women (body mass index IBMIJ = 48 ± 7 kg . m-2, mean ± standard deviation) aged 36 ±8 years before and at intervals after gastric restrictive (GR; n = 12) and malabsorptive (MA; n = 13) operations for obesity. Results are compared with a control group of 26 healthy normal-weight women (BMI = 21 ± 2). Before operation, the obese patients had absolute elevations of all water compartments compared with controls, with significantly higher ratios of Nae to TBK (1.17 ± 0.13 versus 0.91 ± 0.10; p < 0.05) and ECW to intracellular water (ICW) (E/I = 0.82 ± 0.17 versus 0.63 ± 0.06; p < 0.05). After weight loss of 52 ± 20 kg in MA and 47 ± 19 kg in GR patients (nonsignificant between groups) to a stable level 22 ± 8 months after operation, there were statistically significant reductions in TBW, ICW, TBK, and Nae in both groups, but a significant reduction in ECW only after GR. Adjusting for preoperative weight, duration of follow-up, and rate of weight loss, E/I was greater after MA than GR (1.09 ± 0.25 versus 0.82 ± 0.14; p < 0.05). The elevated preoperative E/I ratio did not normalize with weight loss after surgery, and the response was related to the type of operation. The finding remains to be explained although the increased E/I after MA may reflect mild protein-calorie malnutrition not detectable in the blood. The persistence of elevated E/I with significant weight loss after GR might imply an intrinsic or irreversible imbalance of fluid distribution in obese patients. OB
From the Department of Surgery,t SUNY HSC Brooklyn, Body Composition Unit,f St. Luke's-Roosevelt Hospital Center, Columbia University, New York; and the Department of Physiology,§ SUNY HSC Brooklyn, New York
part to the high ratio of extracellular to intracellular water content (ICW) of adipose tissue found in obesity.2'3 The cause and possible physiologic significance of this finding is unknown. Although relative increases in ECW are commonly attributed to protein-calorie malnutrition,4'5 with edema and inability to retain crystalloid fluid in the intravascular space, this is an unlikely cause in untreated obesity. Studies of effects of therapeutic weight loss on the increased ECW in obesity might demonstrate whether this increase is reversible. Surgical treatment of obesity offers an opportunity to study changes in body composition associated with large and sustained weight loss, with a view to determining reversibility of the abnormal fluid distribution in obesity. Earlier studies with various techniques of the effects on body composition of two physiologically different operations: gastric restrictive (e.g., vertical banded gastroplasty6) and malabsorptive (e.g., jejunoileal bypass7) yielded equivocal results.8'6 Such studies rarely measured extracellular water directly, instead relying on assumptions about hydration of the lean body that have not been validated in obese patients.' Here for the first time, we present studies using independent, direct methods to determine ECW before and after gastroplasty and intestinal bypass in severely obese patients.
ESITY IS ACCOMPANIED by a variety of changes
in body composition. In addition to the obvious
increase in adipose tissue mass, there is a relative expansion of extracellular water (ECW),' which is due in
Methods
Address reprint requests to John G. Kral, M.D., Ph.D., Department of Surgery, Box 40, SUNY HSC at Brooklyn, 450 Clarkson Avenue, Brooklyn, NY 11203. Accepted for publication November 25, 1991. * Current address: Gerontology Group, Center for Studies of Sensory Impairments, Aging and Metabolism, Guatemala.
Subjects
Twenty-five obese women (aged 36 ± 8 years, mean ± standard deviation) were studied at baseline before anti-
69
Ann. Surg. . July 1992
MAZARIEGOS AND OTHERS
70
obesity surgery (Table 1) and at postoperative intervals. None of the patients had clinically significant heart failure or respiratory disease. Patients with diabetes, hypertension, or renal or hepatic disease were excluded. Patients had no history of malignancy or ofprior surgical treatment of obesity. They did not regularly take any medication known to affect body composition or nutritional state. A nonobese control group consisted of 26 healthy women matched for height and age (age, 38 ± 13 years).
measured in a 4-pi whole-body 40K counter, with an attenuation correction applied according to body weight.'8 Exchangeable sodium was measured from blood samples approximately 18 hours after oral administration of 24Na. Intracellular water (ICW) was obtained by subtracting ECW from TBW. The relative fluid distribution was expressed as the ECW/ICW ratio (E/I). Intracellular potassium, Ki, was calculated in mEq/L from: TBK - serum potassium X ECW/ICW.
Blood Chemistry Routine serum analyses were made of electrolytes, including magnesium and calcium, albumin, globulin, total protein, iron, and iron-binding capacity.
Surgical Procedures
Body Composition Tests Tests were made in the morning after overnight fasting. Height was measured to ±5 mm and weight to ±0.1 kg in patients wearing a hospital gown without shoes. Total body water (TBW), extracellular water (ECW), total body potassium (TBK), and exchangeable sodium (Nae) were measured before the weight-reduction surgery and periodically at 6- to 12-month intervals after surgery. All subjects gave written consent, approved by the institutional review board. The methods included in this protocol have been described in detail elsewhere.'7",8 Total body water was determined from the 3-hour dilution of 200 uCi tritium (3H20), with a precision of ± 1.2%. Extracellular water was measured as the volume distribution of 50 ACi Na235SO4 by zero-time extrapolation from samples at 120, 140, 160, and 180 minutes.'7 Total body potassium was TABLE 1. Body Composition in 25 Obese Women and 26 Nonobese Control Women
Group
Age (yr) Height (cm) Weight (kg) BMI (kg/mr2) TBW (L) ECW (L) ICW (L) TBK (mEq) Nae (mEq)
E/I Nae/TBK TBK/TBW
Obese
Control
p
36.5 ± 8.3 162.3 ± 6.0 127.0 ± 18.8 48.8 ± 6.8 44.7 ± 6.7 19.9 ± 3.8 24.8 ± 4.2 3096 ± 508 (24) 3455 ± 422 (20) 0.82 ± 0.17 1.17 ±0.13(18)
37.9 ± 13 164 ± 7 56.6 ± 4.6 21 ± 2 31.4 ± 2.8 12.1 ± 1.0 19.3 ± 2.1 2568 ± 257 (25) 2334 ± 243 0.63 ± 0.06 0.91 ±0.10(25) 82 ± 6 (25)
NS NS
