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PubMed1995

Cold-induced changes in circulating levels of catecholamines and thyroid hormones are modulated by energy intake in newborn pigs.

Newborn pigs were kept at a low ambient temperature from 6 until 54 h of age and supplied with a limited (LI, 415 g (kg body weight)-1) or a high (HI, 655 g (kg body weight)-1) intake of milk. At the end of the treatment, both groups had similar deep body temperatures and metabolic rates. However, plasma adrenaline and noradrenaline levels were, respectively, 5.8- and 3.0-fold lower (P < 0.01) in HI than LI piglets, whereas plasma 3,5,3'-triiodothyronine (T3) was 1.5-fold higher (P < 0.01) in HI piglets. It is concluded that the hormonal control of cold-induced thermogenesis is modulated by energy intake, with catecholamines and thyroid hormones acting in a closely related and complementary manner.

Aging↗
PubMed2000

Effects of reduced energy intake on the biology of aging: the primate model.

Dietary energy restriction is the only proven method for extending lifespan and slowing aging in mammals, while maintaining health and vitality. Although the first experiments in this area were conducted over 60 y ago in rodents, possible applicability to primates has only been examined in controlled studies since 1987. Our project at the National Institute on Aging began with 3-0 male rhesus and 30 male squirrel monkeys of various ages over their respective life spans. Subsequently, it has been expanded to include female rhesus monkeys, and several other laboratories have initiated related studies. Experimental animals are generally fed 30% less than controls, and diets are supplemented with micronutrients to achieve undernutrition without malnutrition. These calorically restricted (CR) monkeys are lighter, with less fat and lean mass than controls. Bone mass is also slightly reduced, but in approximate proportion to the smaller body size. CR animals mature more slowly and achieve shorter stature than controls as well. Metabolically, CR monkeys have slightly lower body temperature and initial energy expenditure following onset of restriction, and better glucose tolerance and insulin sensitivity. The latter suggest a reduced predisposition towards diabetes as the animals age. Other potential anti-disease effects include biomarkers suggestive of lessened risk of cardiovascular disease and possibly cancer. Candidate biomarkers of aging, including the age-related decrease in plasma dehydroepiandrosterone sulfate (DHEAS), suggest that the CR animals may be aging more slowly than controls in some respects, although sufficient survival data will require more time to accumulate. In summary, nearly all CR effects detected in rodents, which have thus far been examined in primates, exhibit similar phenomenology. Potential applicability of these beneficial effects to humans is discussed.

Aging↗
PubMed2001

Exendin-4 reduces fasting and postprandial glucose and decreases energy intake in healthy volunteers.

Exendin-4 is a long-acting potent agonist of the glucagon-like peptide 1 (GLP-1) receptor and may be useful in the treatment of type 2 diabetes and obesity. We examined the effects of an intravenous infusion of exendin-4 (0.05 pmol. kg(-1). min(-1)) compared with a control saline infusion in healthy volunteers. Exendin-4 reduced fasting plasma glucose levels and reduced the peak change of postprandial glucose from baseline (exendin-4, 1.5 +/- 0.3 vs. saline, 2.2 +/- 0.3 mmol/l, P < 0.05). Gastric emptying was delayed, as measured by the paracetamol absorption method. Volunteers consumed 19% fewer calories at a free-choice buffet lunch with exendin-4 (exendin-4, 867 +/- 79 vs. saline 1,075 +/- 93 kcal, P = 0.012), without reported side effects. Thus our results are in accord with the possibility that exendin-4 may be a potential treatment for type 2 diabetes, particularly for obese patients, because it acts to reduce plasma glucose at least partly by a delay in gastric emptying, as well as by reducing calorie intake.

Acetaminophen↗
PubMed1986

Dietary thermogenesis in obesity: fat feeding at different energy intakes.

Eight obese and eight lean women were studied in a metabolic unit for up to 4 weeks to assess the thermogenic response to fat overfeeding. An extra 4.3 MJ fat were given to both obese and lean groups for 6 days after a preliminary weight-maintenance diet. The fat overfeeding was repeated following a period of semistarvation. The obese women initially had a higher 4-h expenditure (9.9 +/- 1.1 MJ) than the lean (7.4 +/- 0.6 MJ). Fat overfeeding induced a variable increase in energy output (340 +/- 197 kJ in the obese and 612 +/- 147 kJ in the lean) amounting to 7.8 +/- 4.5 percent of the supplement's energy in the obese and 14.2 +/- 3.4 percent in the lean. The response to the fat supplement during semistarvation remained low in the obese at 3.6 +/- 4.9 percent but fell substantially in the lean (8.1 +/- 3.8 percent). These results suggest that there is a flexibility in the normal thermogenic response to fat in lean subjects but a reduced response in those with familial obesity.

Dietary Fats↗
PubMed1986

Effects of restriction of dietary energy intake during the prepubertal period on secretion of luteinizing hormone and responsiveness of the pituitary to luteinizing hormone-releasing hormone in heifers.

The working hypothesis that a low plane of nutrition during the prepubertal period delays puberty in heifers by retarding the prepubertal increase in secretion of luteinizing hormone (LH) was investigated. Secretion of LH and the responsiveness of the pituitary to LH-releasing hormone (LHRH) were compared in heifers fed a growing diet (which allowed spontaneous occurrence of puberty; n = 12; control) or an energy deficient diet (which delayed puberty; n = 11; delayed) during the prepubertal period. The dietary treatments were initiated when the heifers were 299 +/- 14 (mean +/- SD) d of age (d 0 of the experiment) and continued until d 175 of the experiment (474 +/- 14 d of age). Weight gains were .79 +/- .05 (mean +/- SE) and .21 +/- .03 kg X head-1 X d-1 for control and delayed heifers, respectively. Puberty occurred on d 120 +/- 14 of the experiment (428 +/- 13 d of age) in control heifers, whereas none of the delayed heifers attained puberty during the feeding period. Serum concentration of LH and the frequency of LH pulses increased rapidly during the 175-d feeding period in control heifers. In delayed heifers, serum LH concentration increased less rapidly and no increase in pulse frequency was detected during the experimental period. Amplitude of LH pulses tended to be higher in control than delayed heifers. Responsiveness of LH secretion to LHRH was lower in delayed than control heifers. It is speculated that failure of secretion of LH to increase is the causative factor for delayed puberty when dietary energy is limited during the prepubertal period in heifers.

Animals↗
PubMed2000

Energy expenditure, energy intake and prevalence of obesity after therapy for acute lymphoblastic leukemia during childhood.

OBJECTIVES: To investigate the prevalence and potential risk factors of obesity after therapy for childhood acute lymphoblastic leukemia (ALL). STUDY DESIGN: 39 ALL patients (age 10.7-20.5 years) who were in first remission for 3.4-14.6 years after standardized treatment with chemotherapy plus cranial irradiation (n = 25) or with chemotherapy alone (n = 14) were examined. After fasting overnight, the following parameters were investigated: body mass index (BMI) of patients and their parents; patients' BMI before ALL therapy; serum free thyroxin, growth hormone-dependent factors, estradiol, testosterone, cortisol, leptin and c-peptide; fat-free mass (bioelectrical impedance); resting metabolic rate (RMR, indirect calorimetry); caloric intake (24-hour recall); and physical activity (questionnaire). RMR data were applied to the fat-free mass and compared with 83 controls. RESULTS: The prevalence of obesity (criterion: BMI > 2 SDS) was significantly (p < 0.05) higher after ALL therapy (38%; irradiated patients 48%, non-irradiated patients 21%) than before therapy (3%). Compared to non-irradiated patients, irradiated patients had significantly lower RMRs (-1.07 +/- 0.24 vs. -0.32 +/- 0.21 SDS; p < 0.05), reduced physical activity levels (1.41 +/- 0.03 vs. 1.52 +/- 0.03; p < 0.05), and lower concentrations of insulin-like growth factor-binding protein-3 (-0.65 +/- 0.17 vs. 0.25 +/- 0.33 SDS; p < 0.05) and of free thyroxin (1.17 +/- 0.06 vs. 1.38 +/- 0.08 ng/dl; p < 0.05). Caloric intake was adequate. CONCLUSIONS: After ALL during childhood, patients face a higher risk of obesity. In the cranially irradiated patients, the likely causes are low physical activity, RMRs and hormonal insufficiency.

Adolescent↗
PubMed1985

The effect of energy intake and expenditure on the recovery of 13CO2 in the parenterally fed neonate during a 4-hour primed constant infusion of NAH13CO3.

The use of 13CO2 excretion to measure the oxidation of 13CO2 labeled substrates is increasing as it is both noninvasive and lacks the radiation exposure associated with the use of 14C. No standards are available for 13CO2 recovery in breath from the bicarbonate pool in the neonate. A primed constant infusion of NaH13CO3 over 4 h was used with open circuit indirect calorimetry in 15 appropriate for gestational age newborn infants (gestational age 28-39 wk; postnatal age 2-52 days), on varying amounts of intravenous feeding (37-114 kcal X kg-1 X day-1). Following a bolus of 6.9 mumol X kg-1 of NaH13CO3, a maintenance infusion of 4.6 mumol X kg-1 X h-1 was started. The 13C enrichment in breath rose rapidly to reach a plateau by 90 min with less than 5% variation of the plateau. Recovery of the tracer in breath ranged from 69.6-83.5% and was significantly correlated with 1) energy intake (37-114 kcal X kg-1 X day-1); 2) metabolic rate (34.6-56.1 kcal X kg-1 X day-1); 3) VCO2 (4.86-7.43 ml X kg X -1 X min-1). There was no correlation with the level of protein or fat intake. We provide an equation that can be used to calculate the correction factor when doing constant infusion substrate oxidation studies with a 13C label in neonates.

Bicarbonates↗
PubMed1985

Physiology of energy intake: an inventory control model.

An inventory control model is used to describe the regulation of depot fat and contribution made to the satiation process by putative feedback signals. In the two bin inventory control system, adipose tissue is viewed as a large storage reservoir which is periodically refilled by means of adjustments made in meal consumption. The gastrointestinal tract is viewed as a smaller bin which triggers renewed food ingestion when it becomes partially emptied. However, reduction in the contents of the adipose tissue bin below a critical level (reorder point quantity) generates a signal to the brain that appropriately modulates meal size and intermeal interval. Because this model evolved to cope with worst case situations, a strong bias for storage in time of plenty is inherent in the system. This fact helps to account for the high prevalence of obesity in energy-rich societies, where, in contrast to the situation that obtains in primitive societies, the energy cost of obtaining food is minimal.

Adipose Tissue↗
PubMed1980

Protein utilization in correlation to energy intake.

The effect of 14 days' intake of mounting quantities of fats and energy on a constant optimum utilizable amount of dietary protein was studied in weaned rats weighing 60 g. Growth (PER, NPR) and utilization (NPU--body, LPU--liver) parameters of biological protein value were determined, supplemented by a study of the course of the antithetical processes of gluconeogenesis and glycolysis, of the pentose cycle, the citric acid cycle and of transamination processes in the animals' liver. According to the maximum PER, NPR, NPU and LPU values, a 14 days' intake of 59.2 g fats and 4.518 MJ, corresponding to a diet containing 10% protein, 30% fat and 2.274 MJ, had the best effect on the optimum utilizable amount of casein (21 g/14 days). A diet containing 35% and 40% fat stimulated gluconeogenesis, followed by a transamination process and inhibition of glycolysis, the citric acid cycle and lipogenesis (depression of pentose cycle activity and a decrease in the amount of body fat), and simultaneously reduced the values of all four parameters of protein biological value. The results demonstrate that very best diet for newly weaned rats is one containing 10% high quality protein, 30% fat and 2.274 MJ.

Animals↗
PubMed2002

Progesterone clearance rate in lactating dairy cows with two levels of dry matter and metabolisable energy intakes.

The aim of these studies was to determine the effect of levels of dry matter (DM) and metabolisable energy (ME) intakes on clearance rate of progesterone (P4) in dairy cows. Thirty-two lactating Holstein-Friesian cows were selected for the study and were fed indoors in individual stalls for a period of 5 weeks. They were individually offered a diet of combinations of pasture, hay and pelleted cereal grain to achieve two different levels of DM and ME. In the first trial, 16 cows were allocated to two groups: (i) high DM (HDM), and (ii) low DM (LDM) intakes, while the amount of ME intake was constant. In the second trial, 16 cows were allocated to two groups: (i) high ME, and (ii) low ME intakes with similar amount of DM intake. A GnRH-agonist (deslorelin) was initially implanted in the ear of each cow to block endogenous P4 secretion. Then 3 weeks later, a CIDR device was inserted into the vagina of each cow and left in place for 11 days. Chromic oxide (Cr(2)O(3)) capsules were administered to allow daily faecal output (FO) to be estimated. Daily blood, faecal and milk samples were taken during the period of the experiment for P4 and faecal P4 metabolites analyses. Trial 1: The average milk yield was similar among cows in high and LDM intake groups (26.7 versus 25.0 l per day, P = 0.2). The average daily FO was 7.8 kg DM in the HDM and 5.7 in the LDM cows (P < 0.0001). Average daily DM intakes were 17.3 kg and 15.4 kg in the HDM and LDM groups, respectively (P < 0.0001). The average plasma P4 concentrations were similar between the two groups (1.56 versus 1.60 ng/ml, P = 0.7) but milk P4 concentrations were higher in LDM cows (4.6 versus 3.6 ng/ml, P = 0.02). The average daily excretion rate of P4 into the milk was higher in LDM cows (122.3 versus 88.5 microg, P = 0.002). The concentrations of faecal P4 metabolites (FP4M) were not influenced by the level of daily DM intake (2.85 versus 2.90 microg/g, P = 0.6). The average daily yields of FP4M were higher among cows in the HDM group (23.2 versus 16.3mg, P = 0.01). Trial 2: The average milk yield was 31.2l per day in HME cows compared to 25.0l per day in LME cows (P < 0.0001). The average daily FO was 7.8 kg DM in LME and 5.8 kg DM in HME cows (P < 0.0001), and the average DM content of faeces was higher in LME cows (15.8 versus 12.7%, P = 0.01). The average daily ME intake was 213MJ per day in HME group compared to 183MJ per day in LME group (P<0.0001). The average plasma and milk P4 concentrations were similar between the two groups (plasma P4 = 1.54 versus 1.56 ng/ml, P = 0.4; milk P4: 3.7 versus 3.6 ng/ml, P = 0.6). The average daily excretion rate of P4 into the milk was higher in HME cows (114 versus 88.5 microg, P = 0.03). Concentrations of FP4M were not influenced by the level of daily ME intake (2.5 versus 2.85 micro g/g, P = 0.08). However, daily yields of FP4M were greater in the LME group (23.2 versus 14.4 mg, P = 0.01). In conclusion, this study was unable to establish a relationship between the level of DM and ME in the diet with the excretion rates of FP4M metabolites and plasma P4 concentrations.

Animal Feed↗
PubMed1995

[Effect of protein and carbohydrate preloads on food and energy intakes in preschool children with different nutritional status].

Three preloads: high in simple carbohydrates (fruit juice), high in complex carbohydrates (banana) and high in protein (chicken meat), were tested in two groups of preschool children (56), aged 2 to 4 years from both genders. One group had a normal weight for height and the other high weight for height. The preload were given thirty minutes before lunch. The lunches consisted in a legume dish, apple and a milk dessert. Children were stimulated but not forced to eat and the amount of foods consumed was determined by differential weighing. The results showed that overweight children had a lower consumption at lunch that normal children when the high carbohydrate preloads were tested. High simple carbohydrate preload, 338,2 +/- 87.0 vs 350,9 +/- 75.9, high complex carbohydrate preload, 336.2 +/- 109.6 vs 375.4 +/- 89.4. High protein preload had not effect on the lunch consumption in the two groups of children studied. When an analysis by age of children were made, dividing the normal and overweight children in two groups, 24 to 36 months and 36 to 48 months, it was demonstrated that differences in lunch consumption between the normal and overweight children was derived essentailly from the results obtained in children of 24 to 36 months, high simple carbohydrate preload 282.3 +/- 88.9 g vs. 318.5 +/- 80.0 g and in the high complex carbohydrate preload, 262.6 +/- 98.9 g vs 364.5 +/- 116.3 g. When energy intake derived from food consumption was analyzed, the same tendency described for food consumption was demonstrated. The results presented show a different response of overweight children to the high carbohydrate preloads consumed before lunch, specially in children aged 24 to 36 months. This findings are important since they give an experimental information that can be utilized to find metabolic answers in relation to the onset of obesity in the childhood and to establish dietary recommendations in order to alleviate the risk of obesity in children.

Analysis of Variance↗
PubMed2004

Effects of short-term overfeeding on hunger, satiety, and energy intake in thin and reduced-obese individuals.

BACKGROUND: Certain individuals appear to be resistant to weight gain in an obesigenic environment, yet the mechanisms for this adaptation are unclear. These individuals may sense positive energy balance more appropriately than those individuals prone to weight gain. RESEARCH METHODS AND PROCEDURES: Thirteen thin (7 women, 6 men) and 9 reduced-obese (5 women, 4 men) individuals were studied. Measures of intake were obtained using visual analog scales before and after each meal during eucaloric feeding and during three days of 50% overfeeding. Ad libitum energy intake was measured post-overfeeding. RESULTS: Overfeeding resulted in a significant reduction in pre-meal hunger in the thin (68+/-6 to 41+/-6 mm, p<0.0001) compared to the reduced-obese individuals (63+/-7 to 65+/-7 mm, p=0.67). There was a significantly greater increase (p=0.0016) in post-meal satiety scores during overfeeding in the thin (65+/-4 to 88+/-4 mm, p<0.0001) compared to the reduced-obese individuals (72+/-5 to 80+/-5 mm, p=0.04). Thin women had a 30% reduction in daily energy intake (1831+/-47 to 1273+/-79 kcal/day, p=0.005) after overfeeding while no difference was seen in the thin men or reduced-obese group. DISCUSSION: Thin individuals appear to sense positive energy balance more appropriately with changes in measures of intake than reduced-obese individuals. These findings are especially true in thin women.

Adaptation, Physiological↗
PubMed1995

Exercise and energy intake: effect of substrate oxidation.

The main objective of this study was to evaluate the short-term effect of exercise-induced alteration in fat oxidation on postexercise spontaneous energy and macronutrient intakes. Eleven young males were submitted to two randomly assigned sessions of 48 h each, during which they were requested to eat in the laboratory. One of these sessions was preceded by a 90-min exercise bout at an intensity of 60% VO2max. During both sessions, subjects ate ad lib food with a fat content conforming to the recommendations of nutrition agencies with a food quotient (FQ) > or = 0.85. Results showed that there was no significant change in postexercise energy and macronutrient intakes in comparison with the sedentary session. However, when subjects were subdivided into two groups on the basis of the respiratory quotient (RQ) measured during exercise, men with a low RQ (high fat oxidation) were characterized by a reduced postexercise increase in energy intake relative to the energy cost of exercise (ECE), i.e., they were more predisposed to be in negative postexercise energy balance compared to those exhibiting a high RQ. Accordingly, exercise RQ was positively associated with postexercise energy and lipid balance. These results show that postexercise energy balance partly depends on the composition of the substrate mix oxidized during exercise.

Adult↗
PubMed1990

Energy metabolism of broiler breeder hens. 1. The partition of dietary energy intake.

The partitioning of AME intake (MEI) and recovered energy (RE; defined as MEI minus heat production) was investigated on Hubbard broiler-breeder hens (BB) by using indirect calorimetry and energy balance. The regression of RE on MEI was linear (R2 = .96; P less than .01) with a slope of .817 +/- .024 (SE) and a y-intercept of -238.3 +/- 10.7 (SE). The maintenance energy requirement was 292 kilojoule (kJ) per kg per day (367 kJ per kg.75 per day). The regression of body RE, defined as RE minus egg energy, on MEI was linear (R2 = .96; P less than .01) with a slope of .799 +/- .045 (SE) and a y-intercept of -344.9 +/- 19.7 (SE). Therefore, an MEI of 432 kJ per kg per day was required by BB hens to maintain body energy equilibrium when they were laying at approximately 85% production. At an MEI of less than 432 kJ per kg per day, body energy was used for egg production. The AME cost of depositing 1 kJ of body, egg, protein, or fat energy was (mean +/- SE) 1.21 +/- .06, 91 +/- .32, 1.96 +/- .71, and 1.05 +/- .15 kJ, respectively. The results indicate that individually caged BB hens between 28 and 36 wk of age in a thermal-neutral environment (21 C) require approximately 1.6 megajoule (MJ) of AME per bird per day for normal growth (3 g/per day) and egg production (85%).

Animals↗
PubMed1981

Food intake and energy expenditure of male and female farmers from Upper-Volta.

1. The energy balance of eleven male and fourteen female adult farmers was measured for 6 d after the harvest, in December-January. Their energy intake was recorded by weighing their food consumption and their energy expenditure was determined using indirect calorimetry. 2. Body-weight, expressed as percentage of expected weight-for-height was 91 and 86% of the Inter-departmental Committee on Nutrition for National Development (1963) standard for women and men respectively. 3. The staple foods were sorghum (Sorghum vulgare) and millet (Pennisetum typhoïdes); carbohydrates, fat and protein supplied approximately 80, 13 and 12% of the total energy of the diet respectively. 4. In the male group, the mean energy intake (9.0 MJ (2148 kcal)) was in good agreement with the average energy output (8.91 MJ (2130 kcal)). By contrast, in the female group, the mean energy expenditure (8.11 MJ (1941 kcal)) exceeded the mean energy intake (6.3 MJ (1515 kcal)) and the deficit was statistically significant. 5. This study allows an evaluation of the adequacy of food intake for subjects living in a particular hostile environment, by using their actual energy output instead of current standard values. The energy deficit found for female farmers whose energy intake was similar to that reported in other developing countries emphasizes the need for a better understanding of the regulation of energy balance in such conditions.

Activities of Daily Living↗
PubMed2001

Gender differences in carbohydrate loading are related to energy intake.

We demonstrated that female endurance athletes did not increase their muscle glycogen concentration after an increase in the dietary carbohydrate intake (58 --> 74%), whereas men did (Tarnopolsky MA, SA Atkinson, SM Phillips, and JD McDougall, J Appl Physiol 78: 1360-1368, 1995). This may have been related to a lower energy or carbohydrate intake by the women or due to an inherent gender difference in glycogen storage capacity. We examined whether well-trained men (n = 6) and women (n = 6) increased muscle glycogen concentration after an increase in both the relative (58 --> 75%) and absolute energy and carbohydrate intake and whether potential gender differences were related to muscle hexokinase enzyme activity. Subjects were randomly allocated to three diets [Hab, habitual; CHO, high carbohydrate (75%); and CHO + E, extra energy + CHO ( upward arrow~34%)] for a 4-day period before a muscle biopsy for analysis of total and pro- and macroglycogen and hexokinase activity. Total glycogen concentration was higher for the men on the CHO and CHO + E trials compared with Hab (P < 0.05), whereas women increased only on the CHO + E trial compared with Hab (P < 0.05). There were no gender differences in the proportion of pro- and macroglycogen or hexokinase activity. A low energy intake may explain the previously reported lower capacity for women to glycogen load compared with men.

Adult↗
PubMed1984

Nitrogen balance in men with adequate and deficient energy intake at three levels of work.

Two studies were conducted to investigate the effects of mild exercise on nitrogen balance in men given diets supplying adequate or slightly limiting energy. In experiment A the diet supplied 91 mg N/kg body weight (0.57 g protein/kg, the FAO/WHO safe level of intake) as egg white; in experiment B the same source was used to provide the 1980 NRC-RDA for adult males, 128 mg N/kg body weight (0.8 g protein/kg). By adjusting energy intake and activity, periods of energy equilibrium and negative energy balance (-15%) were achieved at three levels of activity (X for exercise): no programmed work (0.85X), 1 hour of treadmill walking (1.0X) and 1 hour each of treadmill and cycle ergometry (1.15X). "True" nitrogen balance (TNbal) was more positive or less negative during periods of energy equilibrium as compared to those of energy deficit. This effect of energy balance on TNbal increased with physical activity. At the lower protein intake the mean difference in TNbal between the period of energy equilibrium and that of energy deficit at 1.0X was 0.19 g N/day (nonsignificant difference) and 0.54 g N/day at 1.15X. When protein intake was increased, the difference in TNbal between periods of equilibrium and deficit was significant at all levels of activity: 0.65 g N/day at 0.85X, 0.93 g N/day at 1.0X and 1.09 g N/day at 1.15X. Physical activity was anabolic when energy balance was maintained. In experiment A the addition of 1 hour of exercise (1.0X to 1.15X) spared 2.5 mg N/kg body weight; reducing activity by 1 hour (1.0X to 0.85X) cost 1.4 mg N/kg body weight. In experiment B, TNbal was more positive with increased activity (by 5.9 mg N/kg body weight) and more negative (by 11.5 mg N/kg body weight) when the men were sedentary. During periods of energy deficit, the anabolic effect of activity was also present, although less markedly. When activity increased from 1 to 2 hours in experiment A, TNbal improved by 2.1 mg N/kg body weight and in experiment B, by 3.5 mg N/kg body weight. Thus, circumstances of negative energy balance with adequate protein intake are better tolerated when the energy deficit is generated by physical activity than when it derives from reduced intake; the picture when protein intake is marginal requires further investigation.

Adult↗