Biomedical subjects

M D Schluter

Publications and source records attributed to M D Schluter.

At least 19 recordsLinked to original sources

PubMed2002

Branched-chain amino acid supplementation during bed rest: effect on recovery.

Bed rest is associated with a loss of protein from the weight-bearing muscle. The objectives of this study are to determine whether increasing dietary branched-chain amino acids (BCAAs) during bed rest improves the anabolic response after bed rest. The study consisted of a 1-day ambulatory period, 14 days of bed rest, and a 4-day recovery period. During bed rest, dietary intake was supplemented with either 30 mmol/day each of glycine, serine, and alanine (group 1) or with 30 mmol/day each of the three BCAAs (group 2). Whole body protein synthesis was determined with U-(15)N-labeled amino acids, muscle, and selected plasma protein synthesis with l-[(2)H(5)]phenylalanine. Total glucose production and gluconeogenesis from alanine were determined with l-[U-(13)C(3)]alanine and [6,6-(2)H(2)]glucose. During bed rest, nitrogen (N) retention was greater with BCAA feeding (56 +/- 6 vs. 26 +/- 12 mg N. kg(-1). day(-1), P < 0.05). There was no effect of BCAA supplementation on either whole body, muscle, or plasma protein synthesis or the rate of 3-MeH excretion. Muscle tissue free amino acid concentrations were increased during bed rest with BCAA (0.214 +/- 0.066 vs. 0.088 +/- 0.12 nmol/mg protein, P < 0.05). Total glucose production and gluconeogenesis from alanine were unchanged with bed rest but were significantly reduced (P < 0.05) with the BCAA group in the recovery phase. In conclusion, the improved N retention during bed rest is due, at least in part, to accretion of amino acids in the tissue free amino acid pools. The amount accreted is not enough to impact protein kinetics in the recovery phase but does improve N retention by providing additional essential amino acids in the early recovery phase.

Adult↗

PubMed2002

Rate controlling steps in fatty acid oxidation by unloaded rodent soleus muscle.

In response to decreased usage skeletal muscle undergoes an adaptive reductive remodeling due to the decrease in tension on the weight bearing components of the musculo-skeletal system. Accompanying a shift in fiber type is an increased reliance of carbohydrate metabolism and decreased reliance on fat for energy. These responses have been found with both space flight and ground based models of disuse atrophy including the chronically adapted rodent hind limb suspended (HLS) rat (1, 4-7, 10, 11). In addition, after space flight, the ability of soleus muscle homogenates to oxidize palmitate is decreased. We have previously shown that expression of the mRNA of enzymes involved in beta-oxidation is reduced in the soleus muscle of HLS rats. At the same time mRNA expression of enzymes involved in glycolysis was increased. This study extends these observations to address the question of whether the decrease in beta-oxidation is caused by a reduction in the capacity of the pathway to oxidize fat or the regulation is effected before fatty acids enter the mitochondria, i.e. the reduced capacity of the fatty acid oxidation pathway is because less fat is available for oxidation. The two key steps involved in fatty acid uptake into the cells are lipoprotein lipase and the transport of the free fatty acids produced by lipoprotein lipase into the cell via the carnitine acyltransferase system.

NASA Discipline Regulatory Physiology↗

PubMed2000

[Protein turnover during and after extended space flight].

A 15N-glycine tracer technique was used to study protein turnover in four Russian cosmonauts and two U.S. astronauts who had spent long time aboard the Russian orbital station MIR. As was shown, in space flight protein synthesis falls by 46% on the average, which substantially exceeds estimations made on the basis of data about bed-rested human subjects. Reduction in protein synthesis during space flight is connected with the negative energy balance; therefore, it appears imperative to keep balance between energy intake (foodstuffs) and expenditure by cosmonauts on long-term mission.

Circadian Rhythm↗

PubMed1999

Attenuation of the protein wasting associated with bed rest by branched-chain amino acids.

Bed rest is generally accepted as being an appropriate ground-based model for human spaceflight. The objectives of this study were to test the hypothesis that increasing the amount of branched-chain amino acids (BCAAs) in the diet could attenuate the protein loss associated with bed rest. Nineteen healthy subjects were randomized into two groups according to diet. During the 6 d of bed rest, the diets were supplemented with either 30 mmol/d each of three non-essential amino acids, glycine, serine, and alanine (control group), or with 30 mmol/d each of the BCAAs, leucine, isoleucine, and valine (BCAA group). Nutrition was supplied as a commercially available defined formula diet at a rate of 1.3 x REE. Nitrogen (N) balance and urinary 3-MeH excretion were determined for the 6 d. In our results, the urine-based estimate of N balance was 22.2 +/- 14.4 (n = 9) mg N.kg-1.d-1 and 60.5 +/- 10.1 mg (n = 8) N.kg-1.d-1 for the control and BCAA-supplemented groups, respectively (P < 0.05). Urinary 3-MeH excretion was unchanged in both groups with bed rest. We conclude that BCAA supplementation attenuates the N loss during short-term bed rest.

Adult↗

PubMed1999

Endocrine relationships during human spaceflight.

Human spaceflight is associated with a chronic loss of protein from muscle. The objective of this study was to determine whether changes in urinary hormone excretion could identify a hormonal role for this loss. Urine samples were collected from the crews of two Life Sciences Space Shuttle missions before and during spaceflight. Data are means +/- SE with the number of subjects in parentheses. The first value is the mean preflight measurement, and the second value is the mean inflight measurement. Adrenocorticotropic hormone (ACTH) [27.7 +/- 4.4 (9) vs. 25.1 +/- 3.4 (9) ng/day], growth hormone [724 +/- 251 (9) vs. 710 +/- 206 (9) ng/day], insulin-like growth factor I [6.81 +/- 0.62 vs. 6.04 +/- 0.51 (8) nM/day], and C-peptide [44.9 +/- 8.3 (9) vs. 50.7 +/- 10.3 (9) micrograms/day] were unchanged with spaceflight. In contrast, free 3,5,3'-triiodothyronine [791 +/- 159 (9) vs. 371 +/- 41 (9) pg/day, P < 0.05], prostaglandin E2 (PGE2) [1, 064 +/- 391 (8) vs. 465 +/- 146 (8) ng/day, P < 0.05], and its metabolite PGE-M [1,015 +/- 98 (9) vs. 678 +/- 105 (9) ng/day, P < 0. 05] were decreased inflight. The urinary excretion of most hormones returned to their preflight levels during the postflight period, with the exception of ACTH [47.5 +/- 10.3 (9) ng/day], PGE2 [1,433 +/- 327 (8) ng/day], PGF2alpha, [2,786 +/- 313 (8) ng/day], and its metabolite PGF-M [4,814 +/- 402 (9) ng/day], which were all increased compared with the preflight measurement (P < 0.05). There was a trend for urinary cortisol to be elevated inflight [55.3 +/- 5. 9 (9) vs. 72.5 +/- 11.1 micrograms/day, P = 0.27] and postflight [82.7 +/- 8.6 (8) micrograms/day, P = 0.13]. The inflight human data support ground-based in vitro work showing that prostaglandins have a major role in modulating the changes in muscle protein content in response to tension or the lack thereof.

Adrenocorticotropic Hormone↗

PubMed1999

Protein kinetics during and after long-duration spaceflight on MIR.

Human spaceflight is associated with a loss of body protein. Bed rest studies suggest that the reduction in the whole body protein synthesis (PS) rate should be approximately 15%. The objectives of this experiment were to test two hypotheses on astronauts and cosmonauts during long-duration (>3 mo) flights on MIR: that 1) the whole body PS rate will be reduced and 2) dietary intake and the PS rate should be increased postflight because protein accretion is occurring. The 15N glycine method was used for measuring whole body PS rate before, during, and after long-duration spaceflight on the Russian space station MIR. Dietary intake was measured together with the protein kinetics. Results show that subjects lost weight during flight (4.64 +/- 1.0 kg, P < 0.05). Energy intake was decreased inflight (2,854 +/- 268 vs. 2,145 +/- 190 kcal/day, n = 6, P < 0.05), as was the PS rate (226 +/- 24 vs. 97 +/- 11 g protein/day, n = 6, P < 0.01). The reduction in PS correlated with the reduction in energy intake (r2 = 0.86, P < 0.01, n = 6). Postflight energy intake and PS returned to, but were not increased over, the preflight levels. We conclude that the reduction in PS found was greater than predicted from ground-based bed rest experiments because of the shortfall in dietary intake. The expected postflight anabolic state with increases in dietary intake and PS did not occur during the first 2 wk after landing.

Body Weight↗

PubMed1999

Energy expenditure and balance during spaceflight on the space shuttle.

The objectives of this study were as follows: 1) to measure human energy expenditure (EE) during spaceflight on a shuttle mission by using the doubly labeled water (DLW) method; 2) to determine whether the astronauts were in negative energy balance during spaceflight; 3) to use the comparison of change in body fat as measured by the intake DLW EE, 18O dilution, and dual energy X-ray absorptiometry (DEXA) to validate the DLW method for spaceflight; and 4) to compare EE during spaceflight against that found with bed rest. Two experiments were conducted: a flight experiment (n = 4) on the 16-day 1996 life and microgravity sciences shuttle mission and a 6 degrees head-down tilt bed rest study with controlled dietary intake (n = 8). The bed rest study was designed to simulate the flight experiment and included exercise. Two EE determinations were done before flight (bed rest), during flight (bed rest), and after flight (recovery). Energy intake and N balance were monitored for the entire period. Results were that body weight, water, fat, and energy balance were unchanged with bed rest. For the flight experiment, decreases in weight (2.6 +/- 0.4 kg, P < 0.05) and N retention (-2. 37 +/- 0.45 g N/day, P < 0.05) were found. Dietary intake for the four astronauts was reduced in flight (3,025 +/- 180 vs. 1,943 +/- 179 kcal/day, P < 0.05). EE in flight was 3,320 +/- 155 kcal/day, resulting in a negative energy balance of 1,355 +/- 80 kcal/day (-15. 7 +/- 1.0 kcal. kg-1. day-1, P < 0.05). This corresponded to a loss of 2.1 +/- 0.4 kg body fat, which was within experimental error of the fat loss determined by 18O dilution (-1.4 +/- 0.5 kg) and DEXA (-2.4 +/- 0.4 kg). All three methods showed no change in body fat with bed rest. In conclusion, 1) the DLW method for measuring EE during spaceflight is valid, 2) the astronauts were in severe negative energy balance and oxidized body fat, and 3) in-flight energy (E) requirements can be predicted from the equation: E = 1.40 x resting metabolic rate + exercise.

Adipose Tissue↗

PubMed1999

Plasma amino acids during human spaceflight.

BACKGROUND: The plasma amino acid distribution patterns were measured before, during and after flight on the Space Shuttle. The plasma samples were collected from the four payload crewmembers of the 1993 SLS-2 Columbia Shuttle mission. Samples were taken 45, 15 and 8 d before flight; inflight on days 2, 8 and 12 after launch; post-flight on the day of landing; and again 6, 14 and 45 d after landing. RESULTS: Most of the changes found pertained to the essential amino acids, particularly the branched chain amino acids (BCAA). The principle findings were: a) The plasma aminograms for inflight days 8 and 12 were very similar and both aminograms were very different from that of flight day 2. Flight day 2 was not different from the preflight ground control. b) With increasing time in space, there was an increase in the concentration of leucine and isoleucine in the plasma (p < 0.05). This increase occurred even though dietary BCAA intake was not increased inflight. c) The concentrations of the total essential amino acids and the branched chain amino acids (BCAA) in particular were decreased on the day of landing (p < 0.05).

Amino Acids↗

PubMed1999

Cortisol, insulin and leptin during space flight and bed rest.

Most ground based models for studying muscle atrophy and bone loss show reasonable fidelity to the space flight situation. However there are some differences. Investigation of the reasons for these differences can provide useful information about humans during space flight and aid in the refinement of ground based models. This report discusses three such differences, the relationships between: (i) cortisol and the protein loss, (ii) cortisol and ACTH and (iii) leptin, insulin and food intake.

Adrenocorticotropic Hormone↗

PubMed1998

Plasma leptin influences gestational weight gain and postpartum weight retention.

BACKGROUND: Leptin, a product of the obese (ob) gene, is released from adipocytes. At the same body mass index, women have higher concentrations than men. Thus, during pregnancy, leptin may influence gestational weight gain and retention of a portion of that gain postpartum. OBJECTIVE: We examined the relation between plasma leptin at entry to prenatal care and subsequent changes in weight from entry to prenatal care (at 17 wk gestation, baseline) until 6 mo postpartum. DESIGN: This was an observational study of leptin, gestational weight gain, and postpartum weight retention (at 6 wk and 6 mo postpartum) in 103 low-income pregnant women from Camden, NJ, with a pregravid body mass index (in kg/m2) in the normal range (19.8-26). RESULTS: After potential confounding variables were controlled for, leptin at entry significantly (P < 0.05) predicted weight gain in pregnancy, including measured rate of weight gain (x +/- SEE: 0.25 +/- 0.13 kg x unit log leptin(-1) x wk(-1)), measured rate of third-trimester weight gain (0.37 +/- 0.15 kg x unit log leptin(-1) x wk(-1)), rate of weight gain from recalled pregravid weight (0.23 +/- 0.09 kg x unit log leptin(-1) x wk(-1)), and net rate of gestational weight gain (0.22 +/- 0.09 kg x unit log leptin(-1) x wk(-1)). The leptin concentration at entry also significantly predicted retained weight in the postpartum period (at 6 mo: 7.29 +/- 3.33 kg/unit log leptin at entry) and marginally predicted changes in the sum of skinfold thicknesses (at 6 mo: 14.7 +/- 7.5 mm/unit log leptin at entry). CONCLUSION: These results suggest that a high leptin concentration at entry to prenatal care may predict an increased risk of overweight and obesity in vulnerable women.

Adolescent↗

PubMed1997

Weight loss, the gut and the inflammatory response in aids patients.

UNLABELLED: The objective of this study was to test the hypothesis that the integrity of the large bowel wall in AIDS patients is compromised in a manner that favours the chronic translocation of bacteria and/or products of bacterial metabolism into the bloodstream. When such translocation occurs, it induces a characteristic stress/inflammatory response in the body. Urinary butyrate, a unique product of colonic microbial metabolism, was used to assess gut wall permeability. Excretion of the pro-inflammatory cytokine IL-6 in the urine was used as a marker for the stress/inflammatory response. Four groups of subjects were studied, controls (n = 12), HIV + (n = 35) and AIDS patients with (n = 14) and without (n = 17) weight loss. RESULTS: measurable amounts of interleukin 6 (IL-6) and butyrate were found in the urine of all subjects. There were no significant differences in IL-6 excretion between the controls (0.68 +/- 0.64 pg/ml), asymptomatic HIV + subjects (0.59 +/- 0.37 pg/ml) and AIDS patients without weight loss (1.18 +/- 0.33 pg/ml) but IL-6 levels were significantly higher in the AIDS group with weight loss (4.02 +/- 1.26 pg/ml, P < 0.05). A similar pattern of results was found with interleukin 1 receptor antagonist (IL-1ra). Like IL-6 and (IL-1ra), urinary butyrate levels were increased in the AIDS patients with weight loss (2.83 +/- 0.67 mumol/l) relative to the controls (1.31 +/- 0.13 mumol/l, P < 0.05), with the HIV + patients (1.65 +/- 0.18 mumol/l) and AIDS patients without weight loss (1.90 +/- 0.22 mumol/l) falling in between. The data are consistent with a low, but chronic rate of bacteria and/or bacterial products seeping across a compromised colonic wall causing a chronic low stress response in AIDS patients.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Human skeletal muscle protein breakdown during spaceflight.

Human spaceflight is associated with a loss of body protein. Excretion of 3-methylhistidine (3-MH) in the urine is a useful measurement of myofibrillar protein breakdown. Bed rest, particularly with 6 degrees head-down tilt, is an accepted ground-based model for human spaceflight. The objectives of this report were to compare 3-MH excretion from two Life Sciences shuttle missions (duration 9.5 and 15 days, n = 9) and from 17 days of bed rest (n = 7) with 6 degrees head-down tilt. The bed rest study was designed to mimic an actual Life Sciences spaceflight and so incorporated an extensive battery of physiological tests focused on the musculoskeletal system. Results showed that nitrogen retention, based on excretion of nitrogen in the urine, was reduced during both bed rest [from 22 +/- 1 to 1 +/- 5 mg N x kg(-1) x day(-1) (n = 7; P < 0.05)] and spaceflight [from 57 +/- 9 to 19 +/- 3 mg N x kg(-1) x day(-1) (n = 9; P < 0.05)]. 3-MH excretion was unchanged with either bed rest [pre-bed rest 5.30 +/- 0.29 vs. bed rest 5.71 +/- 0.30 micromol 3-MH x kg(-1) x day(-1), n = 7; P = not significant (NS)] or spaceflight [preflight 4.98 +/- 0.37 vs. 4.59 +/- 0.39 micromol 3-MH x kg(-1) x day(-1) in-flight, n = 9; P = NS]. We conclude that 1) 3-MH excretion was unaffected by spaceflight on the shuttle or with bed rest plus exercise, and 2) because protein breakdown (elevated 3-MH) was increased on Skylab but not on the shuttle, it follows that muscle protein breakdown is not an inevitable consequence of spaceflight.

Bed Rest↗

PubMed1996

Diet and nitrogen metabolism during spaceflight on the shuttle.

Human spaceflight is associated with a loss of body protein. To investigate this problem, dietary intake, nitrogen balance, the whole body protein, and fibrinogen protein synthesis rates were measured on the crews of two Spacelab Life Sciences (SLS) shuttle missions before, during, and after spaceflight. The first mission, SLS-1, lasted 9.5 days, and the second, SLS-2, lasted 15 days. The 15N-glycine method was used for the protein synthesis measurements. The following results were obtained. 1) There was a rapid decline in weight for the first 5 days and then the body weight appeared to stabilize. 2) The mean energy intake preflight was 39.0 +/- 2.5 kcal x kg-1 x day-1 (n = 10). There was a sharp drop in dietary intake on flight day 1, with recovery by the second day, and then energy intake was constant at 30.4 +/- 1.5 kcal x kg-1 x day-1 (n = 12) for the remainder of the flight period (P < 0.05). 3) Nitrogen retention was decreased during flight, with the magnitude of the decrease lessening toward the end of the mission. The daily mean nitrogen balance changed from 58 +/- 9 mg x kg-1 x day-1 (n = 9) preflight to 16 +/- 3 mg N x kg-1 x day-1; P < 0.05; n = 11) in flight, corresponding to a loss of approximately 1 kg of lean body mass over 14 days. 4) Whole body protein synthesis was increased early in flight and on recovery, as was fibrinogen synthesis. We conclude that 1) the rapid readjustment and stabilization of energy intake and the improved nitrogen retention with increasing flight duration are consistent with a rapid metabolic accommodation to the novel environment; and that 2) the increased protein turnover indicates that a metabolic stress response is an important factor in this adjustment process.

Adult↗

PubMed1994

Excretion of IL-6 by astronauts during spaceflight.

Ascent to and living under the microgravity conditions found during spaceflight is an unfamiliar environment for humans. The adaptation to the space environment may be perceived by the body as a stress. On the ground, stress results in increased cytokine activity. The objective of this study was to determine whether spaceflight is associated with increased cytokine activity. The mean daily urinary interleukin-6 (IL-6) excretion rate was measured on 24-h urine pools collected from four payload crew members from 11 days before launch to 7 days after landing for a total of 27 days. In addition, in-flight data were obtained from two orbiter crew members. The experiment was conducted before, during, and after the 1991 9.5-day SLS-1 (Columbia) space shuttle mission. Dietary intake and urine output were monitored continuously for the 27-day period for the four payload crew. Results are as follows: 1) urinary IL-6 excretion and cortisol excretion were increased on the 1st day of spaceflight, suggesting an acute-phase response; 2) elevated levels of IL-6 were not found in the urine on any other days before or during flight; and 3) two of the subjects had markedly increased IL-6 excretion rates after landing.

Diet↗

PubMed1993

Glycerol kinetics with parenteral lipid emulsions (long-chain triglycerides, medium-chain triglycerides, and structured lipids) in rats.

Several studies have reported that parenteral lipid emulsions containing medium-chain triglycerides (MCT) and structured lipids (SL) are better utilized than those containing long-chain triglycerides (LCT). The objective of this study was to test the hypothesis that parenteral LCT require more extensive modification via hydrolysis and reesterification (triglyceride-free fatty acid [TG-FFA] recycling) for effective utilization, whereas MCT and SL do not. As an index of TG-FFA cycling activity, we measured glycerol and palmitate kinetics in rats (204 to 243 g) fed parenterally one of three isocaloric (250 kcal/kg/d) isonitrogenous (1.5 g N/kg/d) diets with half of the nonprotein energy from glucose and the rest from either LCT, LCT plus MCT, or SL for 5 days. Two experiments were performed. On day 5, rats were given a 7-to 8-hour infusion of either 5H2 Glycerol and 1-14C Palmitate bound to albumin to measure palmitate and glycerol kinetics (experiment 1), or U-13C glucose to determine the proportion of endogenous glycerol production derived from glucose (experiment 2). Data are presented as means +/- SEM. Endogenous glycerol production was significantly higher with LCT (11.33 +/- 2.89 mmol/kg/h) than with SL (2.91 +/- 0.62 mmol/kg/h). The value for the physical mixture of LCT plus MCT (5.46 +/- 1.29 mmol/kg/h) fell midway between that for LCT and SL (P = NS). There were no significant differences in palmitate kinetics or oxidation. The increased glycerol production is due to the mobilization of endogenous triglyceride and is consistent with a higher rate of TG-FFA cycling being involved in the metabolism of LCT than of SL.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

Effect of spaceflight on human protein metabolism.

Nitrogen balance and the whole body protein synthesis rate were measured before, during, and after a 9.5-day spaceflight mission on the space shuttle Columbia. Protein synthesis was measured by the single-pulse [15N]glycine method. Determinations were made 56, 26, and 18 days preflight, on flight days 2 and 8, and on days 0, 6, 14, and 45 postflight. We conclude that nitrogen balance was decreased during spaceflight. The decrease in nitrogen balance was greatest on the 1st day when food intake was reduced and again toward the end of the mission. An approximately 30% increase in protein synthesis above the preflight baseline was found for flight day 8 for all 6 subjects (P < 0.05), indicating that the astronauts showed a stress response to spaceflight.

Body Mass Index↗

PubMed1992

Effect of total parenteral nutrition, systemic sepsis, and glutamine on gut mucosa in rats.

The effect of the combination of total parenteral nutrition (TPN) and systemic sepsis on mucosal morphology and protein synthesis was investigated. Rats were given a standard TPN mixture consisting of glucose (216 kcal.kg-1.day-1), lipid (24 kcal.kg-1.day-1), and amino acids (1.5 g N.kg-1.day-1) for 5 days. On the 5th day the rats (n = 37) were randomized into four groups according to diet as follows: 1) control nonseptic on standard TPN, 2) control nonseptic on TPN with glutamine, 3) septic on standard TPN, and 4) septic with the TPN supplemented with glutamine. Twenty hours after the injection of Escherichia coli, the rats were given a 4-h constant infusion of [U-14C]leucine to determine the mucosal fractional protein synthesis rates. The following results were obtained. 1) Histological examination showed that systemic sepsis caused tissue damage to the ileum and jejunum. 2) Glutamine supplementation attenuated these changes. 3) There were no visible changes to the colon either from glutamine supplementation or sepsis. 4) Sepsis was associated with an increase in mucosal protein synthesis and decreased muscle synthesis. 5) Addition of glutamine to the TPN mix further increased protein synthesis in the intestinal mucosa of septic rats.

Animals↗

PubMed1991

Effect of reduced dietary intake on energy expenditure, protein turnover, and glucose cycling in man.

The effect of a 50% reduction in food intake on energy expenditure, protein metabolism, glucose cycling, and body composition was investigated in eight moderately overweight men. The prestudy mean calorie and protein intake was determined for eight subjects. They were then maintained on this diet for 6 weeks (mean +/- SEM, 3,269 +/- 75 kcal/d, 20.0 +/- 0.5 g N/d, period I), after which the diet was reduced uniformly in the major foodstuffs by 50% for the next 4 weeks (1,555 +/- 38 kcal/d, 9.6 +/- 5 g N/d, period II). At the end of each period we measured (1) body fat and fat free mass by underwater weighing, (2) 24-hour energy expenditure by indirect calorimetry in a calorimeter, (3) whole body protein synthesis and breakdown rates with 15N glycine, and (4) glucose cycling between glucose and glucose-6-phosphate and fructose cycling between fructose-6-phosphate and fructose-1,6 bisphosphate with 6,6-D2- and 2-D1-labeled glucose. The results were subjects lost 4.0 +/- 0.1 kg fat (by underwater weighing) during the 4 weeks on the reduced-energy regimen. Protein turnover and glucose cycling were reduced by 20% and 15%, respectively. Twenty-four-hour energy expenditure was 2,553 +/- 166 kcal/d for period I and 2,369 +/- 69 kcal/d for period II, giving a difference of 184 +/- 34 kcal/d between the two periods. In conclusion, (1) although energy intake was reduced by 50%, the decrease in energy expenditure was small due to the buffering effect of body fat.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗