24-hour Energy Research Articles

Energy Intake and Physical Activity in Pima Indians: Comparison with Energy Expenditure Measured by Doubly‐Labeled Water

To test the validity of survey techniques for measuring diet and activity patterns of Pima Indians, sequential 24-hour recalls, a food frequency questionnaire (FFQ), and an activity questionnaire were compared to free-living energy expenditure. Total energy expenditure (TEE) measured by doubly labeled water was 13.27 +/- 2.95 MJ/d for the 12 males (mean +/- SD: 35 +/- 14 yr; 97 +/- 35 kg; 32 +/- 9% body fat) and 11.67 +/- 1.85 MJ/d for the 9 females (31 +/- 13 yr; 106 +/- 32 kg; 49 +/- 6% body fat). Energy intake assessed by 24-hour recall was 13.59 +/- 7.81 MJ/d for men and 9.29 +/- 2.77 MJ/d for women, compared to 12.84 + 2.85 and 9.40 + 2.61 MJ/d for men and women, respectively, by FFQ. Both dietary methods indicated significant underreporting by women when compared to TEE. Energy intake assessed by FFQ was significantly correlated with TEE (r=0.48, p=0.03). This was true with 24-hour recall energy intake only when data from two extremely large alcohol consumers were eliminated (r=0.64, p=0.03, N=19). Although a low level of activity was apparent, the activity questionnaire produced significant correlations with measurements of energy expenditure and therefore represents an important tool for examining the relationship between physical activity and diseases.

24-Hour energy expenditure and substrate oxidation rates are unaffected by body fat distribution in obese women

Twenty-four-hour energy expenditure (EE) and nonprotein respiratory quotient (RQ np) were measured by indirect calorimetry in 19 upper-body-obese (UBO) and 15 lower-body-obese (LBO) women with similar body mass index (BMI) and body fat percent. The measurements were performed in a respiration chamber on a predetermined physical activity program and a controlled diet. No differences between the UBO and LBO groups were found in 24-hour, daytime, and sleeping EE after adjustment for differences in fat-free mass (FFM). Furthermore, no group effect was observed in RQ np, but a positive correlation was found between RQ np and age. Despite the fact that an increased free fatty acid (FFA) turnover has been found in UBO subjects, the present study does not support the contention that upper-body obesity is accompanied by an increased lipid oxidation.

Resting Metabolic Rate Variability as Influenced by Mouthpiece and Noseclip Practice Procedures

Mouthpiece and noseclip introduction affect resting physiologic function (i.e., hyperventilation, anxiety), which can influence a resting metabolic rate measurement. It also is obvious that practice is required to minimize this influence when such apparatuses are used. However, the type of practice that best minimizes this influence has not been established. To determine the effect of acute and longer term practice on measurement variability of resting metabolic rate, 27 healthy, premenopausal women were randomly assigned to one of three groups: (1) a practice group, involving three 10-minute practice sessions 1 day to 1 week before resting metabolic rate was measured (n = 9); (2) an acclimation group, in which each subject acclimated to the mouthpiece and noseclip for 5 minutes before the resting metabolic rate measurement (n = 8); and (3) a control group (no practice) (n = 10). Resting metabolic rate was measured three times for each subject via a 5-minute oxygen uptake in the early morning (5:00 to 8:30 am) after a 25-minute supine rest. Resting metabolic rate measurements (kJ/day) and intraindividual variance estimates, adjusted for age and weight, were calculated to determine which practice group had the lowest resting metabolic rate measurement and the lowest variability around each individual's repeated resting metabolic rate measures. Of the three averaged resting metabolic rate measures, significantly lower 24-hour energy expenditures were found with the practice (5647 kJ) and acclimation (5550 kJ) groups when compared with those of the control group (6077 kJ) (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Norepinephrine turnover and energy expenditure in Pima Indian and white men

There is growing evidence of the involvement of sympathetic nervous system (SNS) activity in determining metabolic rate. Whole-body plasma norepinephrine turnover and its relationship to resting metabolic rate (RMR) and 24-hour energy expenditure (24EE) were compared in 14 Pima Indian men (25 ± 4 years, 96 ± 33 kg, 25% ± 9% fat) and nine white men (25 ± 3 years, 88 ± 43 kg, 17% ± 13% fat). Plasma norepinephrine turnover rate correlated strongly with body surface area ( r = .76 and .54 for clearance and appearance, respectively) and fat-free mass ( r = .74 and .52, respectively). However, independent of body size, there was no difference in either norepinephrine clearance or appearance rates between Pima Indian and white men. Norepinephrine appearance rate correlated positively with absolute values of 24EE and RMR, but not when adjusted for differences in body surface area or fat-free mass. However, norepinephrine appearance rate adjusted for differences in body size correlated with spontaneous physical activity. The results indicate that Pima Indian and white men have similar plasma norepinephrine appearance rates, but Pima Indians tend to be more resistant β-adrenergic stimulation. Although energy expenditure and SNS activity were not directly related, a higher SNS tone may either promote or reflect elevated levels of spontaneous physical activity and therefore influence both energy balance and body composition.

Energy expenditure by indirect calorimetry in premenopausal women: variation within one menstrual cycle

Energy expenditure in relation to the menstrual cycle was determined by indirect calorimetry in premenopausal women. For each subject, three measurements were made within a single menstrual cycle. Energy expenditure measurements coincided with the subject's expected hormonal fluxes of estradiol and progesterone: menstrual phase-both hormones at basal levels; follicular phase-elevated estradiol; and luteal phase-elevated progesterone. In experiment I, resting energy expenditure of 14 women was determined for 1 hour using a canopy system for calorimetry; in experiment 2, 24-hour energy expenditures of 12 subjects were measured in a room-size calorimeter. Blood from fasted (12 hours) subjects was collected following measurements of energy expenditure and analyzed for serum estradiol-17B and progesterone by radioimmunoassay. In experiment 1, resting energy expenditure did not differ within one menstrual cycle; neither estradiol nor progesterone affected resting energy expenditure. In experiment 2, 24-hour energy expenditure was significantly lower ( P < 0.013) during the follicular phase when compared with the menstrual (−3.8%) and luteal (−4.9%) phases. Lowered 24-hour energy expenditure during the follicular phase may in part be due to a decrease in spontaneous activity and exercise. Energy expenditure during sleep, an indicator of metabolic energy expenditure, was significantly greater ( P < 0.0001) during the luteal phase than during the menstrual (+6.7%) and follicular (+5.4%) phases; this was a reflection of increased progesterone ( P < 0.0001). Twenty-four hour energy expenditure (mean ± SEM) during the menstrual, follicular, and luteal phases was 8.86 ± 0.26, 8.52 ± 0.22, and 8.96 ± 0.21 MJ/d, respectively. Corresponding values for energy expenditure during sleep were 5.49 ± 0.09, 5.56 ± 0.10, and 5.86 ± 0.11 MJ/d. The menstrual cycle is a significant contributor to variation in energy expenditure through progesterone-mediated increases in metabolic rate. Variation in metabolic energy expenditure was detectable when the contributory components of 24-hour energy expenditure were measured.

Total energy expenditure in intravenously fed patients measured by the doubly labeled water technique

The potential clinical use of the doubly labeled water (DLW) technique to measure total energy expenditure (TEE) in intravenously fed patients was assessed by applying the technique to 13 stable patients receiving total parenteral nutrition (TPN). TEE was compared with resting energy expenditure (REE), which was measured using a ventilated hood (n = 13), and with 24-hour energy expenditure (24h EE) measured in a whole-body calorimeter (n = 6). Daily measurements of urinary enrichment in 2H and 18O showed predominantly small and covariant fluctuations in elimination rates of these two tracers. The standard error of the estimate (SE FCO2) for the CO 2 production rate (F CO2), which includes additional errors due to variability in isotopic fractionation, was calculated to be 2.65% ± 0.70% of F CO2. TPN-related changes in background isotopic enrichment in subjects who were not dosed with isotope virtually ceased 10 days after starting intravenous feeding. TEE (4.99 ± 1.10 kJ/min), TEE REE (1.21 ± 0.16 kJ/min), TEE/basal metabolic rate ([BMR] 1.31 ± 0.16 kJ/min), and TEE (isotopic)/24h EE (calorimetric; 1.07 ± 0.18 kJ/min) showed wide variability. This study provides some evidence for the validity of the DLW method in selected patients receiving TPN, since significant deviations from the assumptions of the method were not found in the subjects studied. The error associated with 2H sequestration during fatty acid synthesis is likely to be small, but could not be accurately measured. The contributions of activity and thermogenesis to TEE varied greatly, but overlapped with those reported in normal subjects.

The effect of ephedrine/caffeine mixture on energy expenditure and body composition in obese women

Treatment with β 2-agonists promotes fat loss and muscle growth in numerous species, but human studies are lacking. We studied the effect of a compound with β 2-agonistic properties (ephedrine 20 mg/caffeine 200 mg [E+C]). Fourteen obese women were treated with a 4.2-MJ/d diet and either E+C or placebo (P) three times per day for 8 weeks in a double-blind study. Weight-loss was not different in the groups, but the E+C group lost 4.5 kg more body fat and 2.8 kg less fat-free mass (FFM). The decrease in 24-hour energy expenditure (EE) seen in the P group was 10% at day 1 and 13% at day 56, but was only 7% and 8% in the treated group ( P = .044). The higher EE in the E+C group was entirely covered by fat oxidation. These findings provide evidence that promotion of fat loss and preservation of FFM during weight reduction may also be achieved pharmacologically in humans.

The Effect of Ethanol on Fat Storage in Healthy Subjects

Ethanol can account for up to 10 percent of the energy intake of persons who consume moderate amounts of ethanol. Its effect on energy metabolism, however, is not known. We studied the effect of ethanol on 24-hour substrate-oxidation rates in eight normal men during two 48-hour sessions in an indirect-calorimetry chamber. In each session, the first 24 hours served as the control period. On the second day of one session, an additional 25 percent of the total energy requirement was added as ethanol (mean [+/- SD], 96 +/- 4 g per day); during the other session, 25 percent of the total energy requirement was replaced by ethanol, which was isocalorically substituted for lipids and carbohydrates. Both the addition of ethanol and the isocaloric substitution of ethanol for other foods reduced 24-hour lipid oxidation. The respective mean (+/- SE) decreases were 49.4 +/- 6.7 and 44.1 +/- 9.3 g per day (i.e., reductions of 36 +/- 3 percent and 31 +/- 7 percent from the oxidation rate during the control day; P less than 0.001 and P less than 0.0025). This effect occurred only during the daytime period (8:30 a.m. to 11:30 p.m.), when ethanol was consumed and metabolized. Neither the addition of ethanol to the diet nor the isocaloric substitution of ethanol for other foods significantly altered the oxidation of carbohydrate or protein. Both regimens including ethanol produced an increase in 24-hour energy expenditure (7 +/- 1 percent with the addition of ethanol, P less than 0.001; 4 +/- 1 percent with the substitution of ethanol for other energy sources, P less than 0.025). Ethanol, either added to the diet or substituted for other foods, increases 24-hour energy expenditure and decreases lipid oxidation. Habitual consumption of ethanol in excess of energy needs probably favors lipid storage and weight gain.

24-hour energy expenditure and sympathetic activity in postobese women consuming a high-carbohydrate diet.

It has been suggested that the energy expenditure (EE) of formerly obese subjects (postobese) is highly susceptible to the dietary carbohydrate content and that a high dietary carbohydrate-to-fat ratio may increase their 24-h EE. We studied eight obese women before and after weight normalization (postobese state) and compared them with eight matched controls. Twenty-four hour EE, substrate oxidations, and 24-h heart rate were measured in respiratory chambers on a fixed physical program, while the postobese and controls were in macronutrient balance on a high-carbohydrate diet. Mean 24-h EE decreased from the obese to the postobese state (P less than 0.01), but it remained higher in the postobese women than in the controls (8,292 +/- 153 vs. 7,646 +/- 190 kJ/day, P = 0.01). The higher EE in the postobese group was entirely covered by a 22% higher carbohydrate oxidation (P = 0.006). The mean 24-h heart rate, as measured by telemetry, was also higher in the postobese group than in the control group (74 vs. 66 beats/min, P less than 0.03). Plasma norepinephrine (NE) concentrations were greater by 50% in the postobese as compared with the controls (P = 0.004), and differences in plasma NE concentrations entirely accounted for the group difference in 24-h EE and heart rate between postobese and controls, as analyzed by stepwise regression analysis. We conclude that postobese women on a high-carbohydrate-low-fat diet have an enhanced sympathetic nervous system activity, which is responsible for the higher 24-h EE and heart rate. These findings may have implications for understanding the pathophysiology and for the treatment of obesity.

Heat leakage across the abdominal wall and meal-induced thermogenesis in normal-weight and obese subjects

The mechanism behind the meal-induced increase in energy expenditure in humans and its reduction in obesity was examined in 15 normal-weight and seven obese subjects. The subjects were studied by indirect calorimetry in the basal state and during 2 hours after a mixed meal corresponding to 40% of the 24-hour basal energy requirement. Artificial thermal insulation was applied over the abdominal area before the study in seven of the normal-weight subjects. Thermistor catheters were inserted into a hepatic vein, the pulmonary artery, and a systemic artery for blood sampling and recording of blood temperatures. Basal hepatic venous drainage of heat in relation to the splanchnic oxygen uptake in the normal-weight subjects was low (12 ± 1 J/mL O 2) and became even lower after the meal (5 ± 3 J/mL). In the obese individuals and the insulated subjects, blood-drained splanchnic heat amounted to 19 to 21 J/mL oxygen both before and after the meal. The postprandial increase in whole body energy expenditure was diminished both in the obese (12% ± 1% above basal) and in the insulated subjects (15% ± 1%) compared with the noninsulated controls (22% ± 2%). In normal-weight subjects, there is a leakage of heat across the abdominal wall. Reduction or prevention of this leakage by artificial thermal insulation or by obesity is accompanied by a reduction of the postprandial increase in energy expenditure.

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-D 2- and 2-D 1-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. (2) The reductions in protein turnover and glucose cycling could account for approximately 28% and 7% of the 184-kcal/d difference in energy expenditure between the two periods.

Obesity, Diet and Body Temperature

Studies conducted thus far on the pathogenesis of obesity have not clearly determined the role of body temperature in the energy balance. In an attempt to explore this relationship further, research has been undertaken, a part of which is represented by the present investigation carried out on 22 adult males: 11 having a BMI less than or equal to 25 (group A) and 11 with BMI greater than 25 (group B). Body temperature was measured by mouth and on the skin surface (in 4 points according to Ramanathan) on 2 consecutive days (every 30 min from noon to 6:30 p.m.), the 1st day with the participants fasting and the 2nd day after consumption of a meal whose energy content represented a part (45%) of the 24-hour energy intake of the subjects, as previously ascertained by a survey of their food consumption. The study was carried out under frequently checked microclimatic conditions. During the week prior to the measurements, the alimentary consumption of the subjects was monitored by direct weighing for 5 consecutive days. A significant rise in body temperature, probably due to dietary thermogenesis, was observed in group A (internal temperature: F = 13.05; skin temperature: F = 6.48) as well as in group B (internal temperature: F = 24.88; skin temperature: F = 5.35) after the meal. However in group B the skin temperature showed a smaller increase than in group A (delta t degree 0.31 vs. 0.49) and an earlier trend towards the basal values (nearly 5 vs. 6 h after the meal). In both groups a decrease in the skin delta t degrees is evident at 3 and 3.5 h, respectively, after the meal, followed by a more remarkable increase in this difference between the 4th and the 5th hour. The meaning of this decrease as well as the difference in body temperature versus caloric intake is discussed. Normal weight individuals demonstrated a positive correlation (r = 0.83) between usual caloric intake per square meter of body surface and fasting internal body temperature. This correlation was not observed in subjects with BMI greater than 25.

145 ENERGY EXPENDITURE AND BODY COMPOSITION OF BREAST-FED AND FORMULA-FED INFANTS

Top of pageAbstract Breast-fed infants consume less energy than formula-fed infants, but grow at almost the same rate. We hypothesized that breast-fed infants spend less energy and/or store less energy. To test these hypotheses, full term infants were studied at 42 and 84 days of age. Eight infants (4 ♀, 4 ♂) were breast-fed (BF) and 10 infants (6 ♀, 4 ♂) were fed a soy-based formula (FF). 24-Hour energy expenditure (EE) was determined by heart beat counting with calibration of heart rate against indirect calorimetry. Total body water (TBW) was estimated by deuterium dilution (0.5g/kg D2O orally, D in urine by NMR). Fat-free body weight was calculated assuming a water content of 80.4% at 42 days and 80.0% at 84 days of age. Body fat = body wt minus fat-free wt. Results (mean (SD)) are shown for 6 BF and 9 FF infants who have to date completed the study: At 42 d BF infants spent significantly (p< .048, 1-tailed t-test) less energy than FF infants, but at 84 d EE was similar. Body fat was slightly lower in BF infants at both ages. Overall wt gain was somewhat less in BF infants, but composition of gain was similar.

Einfluß von Ernährungsniveau und Geschlecht auf den Energie-erhaltungsbedarf von Broilern und Ratten

In 3 experiments young broiler chickens were supplied on various feeding levels in the growth range between 200 and 2500 g live weight (2.8 and 2.0 in experiment 1, 2.8, 2.3 and 1.8 in experiments 2 and 4, maintenance = feeding level 1.0). In experiments 1 and 2 short-time measurings (30 min) of heat production by means of gas exchange were made at 500, 1000, 1500 and 2000 g live weight in the post-absorptive state and on the maintenance level of feeding. In experiment 1 the heat production of the restrictively fed chickens was in 3 out of the 4 stages of development studied significantly lower by 10-14% than that of the intensively fed ones. In experiment 2 such an effect could not be observed. Fed on the level of energy maintenance, broilers weighing approximately 2000 g (experiment 3) did not show a significant influence of the sex on heat production as a result of 30-minute gas exchange measurings in the post-absorptive state. In experiment 4 24-hour measurings of the energy metabolism were carried out in the growth development in periods of feeding on the maintenance level by means of indirect calorimetry. In the live weight range between 0.9 and 1.3 kg there was only a low, non-significant decrease of the energy maintenance requirement of 4-6% of the highly restrictively fed chickens in comparison to the intensively fed ones. After continued feed restriction (live weight range 1.7-2.2 kg) an energy maintenance requirement reduced by 17% was measured. In an analogously arranged experiment with 24-hour energy metabolism measurings (experiment 5) male Wistar rats in the growth range between 70 and 280 g were supplied on the feeding levels 1.8 and 1.4 resp. In all three periods studied on the feeding level maintenance--beginning at 140-150 g live weight--the highly restrictively fed animals showed a slightly reduced energy maintenance requirement by 8%, 3% (non-significant) and 6% in comparison with the intensively fed animals.

Twenty-four-hour energy expenditure and basal metabolic rate measured in a whole-body indirect calorimeter in Gambian men

By use of a respiration chamber, 24-hour energy expenditure (EE), diet-induced thermogenesis (DIT), and basal and sleeping EE were measured in 20 young rural Gambian men during the "hungry" season (weight, 60.8 +/- 1.4 kg) and in a group of 16 European men matched for body composition (weight, 66.9 +/- 1.9 kg). The 24-h EE was lower in Gambian than in European men (2047 +/- 46 vs 2635 +/- 74 kcal/d, p less than 0.001, respectively). Basal EE and sleeping EE were also lower in Gambian than in European men (1.05 +/- 0.02 vs 1.25 +/- 0.02 kcal/min and 1.0 +/- 0.02 vs 1.18 +/- 0.02 kcal/min, p less than 0.01, respectively). DIT was blunted in Gambian compared with European men (6.3 +/- 0.6% vs 12.1 +/- 0.5%, p less than 0.001 respectively). The net efficiency of walking was greater in Gambian than in European men (23.2 +/- 0.3% vs 20.1 +/- 0.4%, p less than 0.001, respectively). A low basal and sleeping EE, a reduced DIT, and a high work efficiency are important energy-sparing mechanisms in Gambian men, which allow them to cope with a marginal level of dietary intake during the hungry season.

Energy metabolism in human obesity.

Obesity results from a chronic imbalance between energy intake and expenditure. Accurate measurements of total energy expenditure of lean and obese individuals with a respiration chamber have clearly shown that obese individuals expand more energy than lean sedentary subjects. Studies on the body composition of obese individuals reveal that not only the fat mass is enlarged, but the fat-free mass is also increased as compared with that of lean subjects. Since basal metabolic rate is proportional to the fat-free mass, obese subjects have a greater basal metabolic rate than lean controls. The energy cost of weight bearing activities such as walking and standing is related to body weight, and is therefore increased in obese individuals. The thermogenic response to food ingestion, the diet-induced thermogenesis, has been found to be reduced in some groups of obese people, but not in all obese individuals. The thermic effect of glucose or to meal ingestion is blunted in obese subjects with insulin resistance. Any alteration in thermogenic responses to a caloric excess can be important to store or to oxidize part of the excessive energy intake. After weight reduction in obese subjects due to a hypocaloric diet, the total 24-hour energy expenditure decreases by 20 to 25 kcal/day for each kilogram of weight loss. Failure to adapt the every day energy intake accordingly will result in body weight gain and relapse of obesity.

Weight loss leads to a marked decrease in nonresting energy expenditure in ambulatory human subjects

The extent to which the resting and nonresting components of 24-hour energy expenditure decrease after weight reduction has not been prospectively assessed in ambulatory, weight-stable, reduced-obese humans. Accordingly, 24-hour energy expenditure was estimated as the weight-stabilizing (±50 g/d) daily caloric intake of a defined liquid diet in a cross-sectional study of ten reduced-obese subjects after a 23.2% ± 9.4% weight loss and 18 obese subjects at baseline weight. A regression analysis demonstrated an 18% decrease in the mean daily energy requirement of the reduced-obese subjects compared with that of subjects of the same relative body weight who had never dieted. Strong linear relationships were noted between estimated 24-hour energy expenditure and fat-free mass (FFM), and between resting metabolic rate (RMR) and FFM in the subjects at baseline weight. In six reduced-obese men, the 24-hour energy expenditure was only 75.7% ± 5.6% of the value predicted by regression analysis for the decreased FFM. In these six subjects the RMR was 97.4% ± 7.5% of that predicted for the decreased FFM, suggesting that essentially all the energy savings relative to FFM in the reduced-obese state occurred in nonresting energy expenditure. In a subsequent group of seven subjects studied longitudinally before and after a 21.5% ± 2.3% weight loss, the decrease in nonresting energy expenditure accounted for 582 ± 276 kcal/d or 71% of the decrease in estimated 24-hour energy expenditure. These data suggest a decrease in the nonresting energy expenditure of ambulatory reduced-obese individuals, which is greater than previously appreciated. A substantial increase in physical activity would be necessary in any weight loss maintenance program to overcome the energy savings of the reduced-obese state.

Reduced rate of energy expenditure as a risk factor for body-weight gain.

The contribution of reduced energy expenditure to the development of obesity has been a point of controversy. We measured 24-hour energy expenditure (adjusted for body composition, age, and sex), in a respiratory chamber, in 95 southwestern American Indians. Energy expenditure correlated with the rate of change in body weight over a two-year follow-up period (r = -0.39, P less than 0.001). The estimated risk of gaining more than 7.5 kg in body weight was increased fourfold in persons with a low adjusted 24-hour energy expenditure (200 kcal per day below predicted values) as compared with persons with a high 24-hour energy expenditure (200 kcal per day above predicted values; P less than 0.01). In another 126 subjects, the adjusted metabolic rate at rest at the initial visit was also found to predict the gain in body weight over a four-year follow-up period. When the 15 subjects who gained more than 10 kg were compared with the remaining 111 subjects, the initial mean (+/- SD) adjusted metabolic rate at rest was lower in those who gained weight (1694 +/- 103 vs. 1764 +/- 109 kcal per day; P less than 0.02) and increased to 1813 +/- 134 kcal per day (P less than 0.01) after a mean weight gain of 15.7 +/- 5.7 kg. In a group of 94 siblings from 36 families, values for adjusted 24-hour energy expenditure aggregated in families (intraclass correlation = 0.48). We conclude that a low rate of energy expenditure may contribute to the aggregation of obesity in families.

Two-week stimulation or blockade of the sympathetic nervous system in man: Influence on body weight, body composition, and twenty four-hour energy expenditure

Seven lean healthy young men were studied for 6 weeks during exposure to pharmacologic inhibition or stimulation of the sympathetic nervous system. For a period of 2 weeks their β-adrenergic receptors were either blocked with propranolol hydrochloride (160 mg/d) or stimulated with terbutaline sulphate (15 mg/d). After a further 2 weeks of placebo administration (500 mg lactose/d), the subjects crossed over to the drug they had not been taking at the beginning of the experiment for another 14 days. During the last five days of each 2-week period, the subjects consumed a weight-maintaining diet, composed of 12% protein, 48% carbohydrate, and 40% fat. They consumed exactly the same menus on the same days during the subsequent study periods. Body weight and physical activity were measured every day for 6 weeks. Daily heart rate and nitrogen excretion were measured continuously for four days at the end of each 2-week period, the last two days of which were spent in a respiration chamber where energy expenditure and a variety of metabolic parameters were measured. In the respiration chamber on the propranolol, placebo, and terbutaline treatments, respectively, significant differences were observed in mean daily heart rate (65 ± 3,75 ± 4, and 84 ± 4 beats/min), mean sleeping heart rate (51 ± 2, 56 ± 3, and 62 ± 3 beats/min), nitrogen excretion (13.6 ± 0.7, 12.6 ± 0.6, and 11.9 ± 0.6 g/d), fat oxidation (+1,045 ± 95, +1,243 ± 148, and +1,278 ± 84 kcal/d) and thyroid hormones (12.0 ± 0.7, 15.7 ± 0.9, and 17.2 ± 1.0 T 3/T 4 ratio). Although a 24-hour energy expenditure tended to be lower with propranolol (2,820 ± 187 kcal/d) than with the placebo (2,884 ± 174 kcal/d) and terbutaline (2,880 ± 122 kcal/d) treatments, the difference was not significant. The results are discussed in relationship with the possible use of β-adrenergic receptor agonists in the treatment of obesity.

Bioenergetic and metabolic response to continuous v intermittent nasoenteric feeding

Resting thermal energy losses and metabolic balances of N, K, P, Ca, Na, and Mg were compared during continuous and intermittent nasoenteric formula infusion in four healthy men. Each feeding protocol lasted 1 week in a 4-week double crossover experiment. The initial feeding schedule was established randomly. Continuous nasoenteric formula infusion produced no increase in thermal energy losses above the fasting level; energy expenditure fell with sleep to the same extent as with intermittent feeding. Thermal losses were similar during intermittent feeding with the exception of the thermic effect of food that produced an additional average energy loss of 115.7 kcal/d. The total resting and sleeping 24-hour energy expenditure was significantly lower ( P < .01) during continuous formula infusion ( X ± SD for n = 8 balance periods, 1344 ± 119 kcal) compared to intermittent feeding (1457 ± 179 kcal). No significant differences in nutrient absorption or balances of N, Na, Ca, and Mg were detected between the two feeding protocols. In contrast, continuous infusion of formula was accompanied by negative balances of K and the cytosolic portion of P; weight balance was slightly negative. Weight, K, and cytosolic P balances were all positive during intermittent feeding (P = NS, <0.01, and P < .05 compared to respective continuous infusion periods). Hence, 1 week of continuous nasogastric formula infusion is associated with similar nutrient absorption, a significant reduction in thermal energy losses, and equivalent protein (N) balance relative to intermittent feeding. Differences in weight balance between the two feeding protocols can be ascribed largely to fluid and mineral shifts. These results suggest that energy requirements are lower during continuous formula infusion by about 100 kcal/d compared to regular meal ingestion.