Thermic Effect Of A Meal Research Articles

Thorough Mastication Prior to Swallowing Increases Postprandial Satiety and the Thermic Effect of a Meal in Young Women.

There is evidence to support that mastication may contribute to the prevention of weight gain via reduction of appetite sensations and subsequent energy intake. However, the metabolic effect of mastication after consumption of a daily meal, composed of the staple food (rice), soup, main and side dishes, is limited. Therefore, the effect of thorough mastication on greater satiety and the thermic effect of a meal (TEM) was investigated in young women. In study 1, energy expenditure (EE) derived from masticatory muscle activity for 20 min was measured while chewing hard, tasteless, non-caloric gum in seven subjects. In study 2, ten subjects consumed a solid meal performing 30 chews per mouthful (30 CPM), or swallowed the same, pureed meal without chewing (0 CPM) on two separate days, and postprandial EE, substrate oxidation, subjective appetite ratings and autonomic nervous system (ANS) activity for 3 h were examined. Both test meals were iso-caloric (2,510 kJ) and -weighted (884 g), and consumed in 20 min. From study 1, the EE of mastication itself for the 20 min was estimated to be 3.7±0.8 kJ. From study 2, significantly higher TEM (134.2±15.5 vs. 67.8±13.8 kJ/3 h, p<0.001) as well as satiety (p=0.005), and tendency toward greater fat oxidation (p=0.090) and ANS activity (p=0.069) were observed after consumption of the meal with 30 CPM compared to 0 CPM. In conclusion, thorough mastication before swallowing increased postprandial satiety and the TEM in young women, suggesting such eating behavior may be useful for preventing obesity.

Increasing energy flux to decrease the biological drive toward weight regain after weight loss – A proof-of-concept pilot study

Weight loss induces compensatory biological adjustments that increase hunger and decrease resting metabolic rate (RMR), which increase propensity for weight regain. In non-obese adults high levels of physical activity coupled with high energy intake (high energy flux) are associated with higher RMR and reduced hunger. We tested the possibility that a high flux state attenuates the increase in hunger and the decrease in RMR characteristic of diet-induced weight loss. Six obese adults [age (mean±SE)=42±12y; body mass index (BMI)=35.7±3.7kg/m2] underwent measures of RMR, the thermic effect of a meal (TEM), and fasting and postprandial measures of hunger and fullness as well as plasma glucose and insulin. Following weight loss, subjects completed two 5-day conditions of energy balance in random order-Low Flux (LF): sedentary with energy intake (EI)=RMR (kcal/d)×1.35; and High Flux (HF): net exercise energy cost of ∼500kcal/d and EI=RMR (kcal/d)×1.7. RMR was measured daily for each flux condition. The morning following each of the respective experimentally controlled HF and LF conditions (flux day 5), they underwent the same pre-weight loss tests and also reported their perceptions of hunger and fullness during the previous four days of HF and LF, respectively. Average daily RMR was higher during HF (1926±138kcal/day) compared to LF (1847±126kcal/day; P<0.05). Perceived hunger at the end of day was lower (p<0.03) and fullness throughout the day was higher (p<0.02) in HF compared to LF conditions. On day 5 of each flux condition, the thermic effect of a meal and circulating glucose and insulin after the meal did not differ between HF and LF. Following weight loss, compared to a sedentary LF state of energy balance, a short-term HF energy balance state is associated with higher RMR, lower perceived hunger, and greater perceived fullness, all of which could help attenuate the biologic drive to regain weight. Given the pilot nature of this study and the relatively short period of time spent in the high and low flux states, future research is needed to address this research question in a larger sample over a longer time period.

Predictors of body composition and body energy changes in response to chronic overfeeding

ObjectiveWe have previously shown that 24 young lean men (12 pairs of identical twins) subjected to a standardized 353 MJ (84 000 kcal) overfeeding protocol over 100 days exhibited individual differences in body weight and composition gains. The mean (+SD) gains in fat mass (FM) and fat-free mass (FFM) were 5.4+1.9 kg and 2.7+1.5 kg for a total body energy (BE) gain of 221+75 MJ representing 63% of the energy surplus consumed. We report here on the most important baseline correlates of these overfeeding-induced changes with the aim of identifying biomarkers of the response.ResultsBaseline maximal oxygen uptake per kilogram body mass was negatively correlated with gains in weight, FM, and BE (all p<0.05). Enzyme activities indicative of skeletal muscle oxidative potential correlated with gains in FM and BE (all p<0.05). Baseline TSH levels in response to a TRH stimulation correlated positively with changes in FM-to-FFM ratio (p<0.05). Plasma concentrations of androstenediol-sulfate, dehydroepiandrosterone, and 17-hydroxy pregnenolone were negatively correlated with gains in FM and BE (0.01<p<0.05), while level of estrone was negatively and androsterone-glucoronide was positively correlated with FFM gains (p<0.05). Baseline leptin and abdominal fat cell size correlated positively with gains in weight, FM, and BE (p<0.05). When compared to the six highest BE gainers, the six lowest gainers exhibited higher thermic effect of a meal (TEM) and plasma levels of total testosterone, cortisol, estradiol, androstenedione, and androstenediol-sulfate (all p<0.05). High baseline levels of total TEM, testosterone, and androstenediol-sulfate were associated with lower FM gains whereas high baseline levels of FT4 and estrone were found in low-FFM gainers.ConclusionAlthough none of the variables exerted individually an overwhelmingly strong influence on overfeeding-induced changes, baseline FFM, maximal oxygen uptake, muscle oxidative capacity, androgens, and leptin levels were the most consistent significant biomarkers of the responsiveness to chronic overfeeding.

Thermic effect of a meal and appetite in adults: an individual participant data meta-analysis of meal-test trials

BackgroundThermic effect of a meal (TEF) has previously been suggested to influence appetite.ObjectiveThe aim of this study was to assess whether there is an association between appetite and TEF. Second, to examine whether protein intake is associated with TEF or appetite.DesignIndividual participant data (IPD) meta-analysis on studies were performed at the Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark. Five randomized meal-test studies, with 111 participants, were included. The included studies measured energy expenditure (EE) in respiration chambers and pre- and postprandial appetite sensations using Visual Analog Scales (VAS). The primary meta-analysis was based on a generic-inverse variance random-effects model, pooling individual study Spearman's correlation coefficients, resulting in a combined r-value with 95% confidence interval (95% CI). The I2 value quantifies the proportion (%) of the variation in point estimates due to among-study differences.ResultsThe IPD meta-analysis found no association between satiety and TEF expressed as the incremental area under the curve (TEFiAUC) (r=0.06 [95% CI −0.16 to 0.28], P=0.58; I2=15.8%). Similarly, Composite Appetite Score (CAS) was not associated with TEFiAUC (r=0.08 [95% CI −0.12 to 0.28], P=0.45; I2=0%). Posthoc analyses showed no association between satiety or CAS and TEF expressed as a percentage of energy intake (EI) (P>0.49) or TEF expressed as a percentage of baseline EE (P>0.17). When adjusting for covariates, TEFiAUC was associated with protein intake (P=0.0085).ConclusionsThis IPD meta-analysis found no evidence supporting an association between satiety or CAS and TEF at protein intakes ∼15 E% (range 11–30 E%).

Effects of 12 weeks of endurance exercise training on thermic effect of a meal

Effects of 12 weeks of endurance exercise training on thermic effect of a meal

Calcium and Dairy Product Modulation of Lipid Utilization and Energy Expenditure

The purpose of this study was to investigate the impact of dietary calcium or dairy product intake on total energy expenditure (TEE), fat oxidation, and thermic effect of a meal (TEM) during a weight loss trial. The intervention included a prescribed 500-kcal deficit diet in a randomized placebo-controlled calcium or dairy product intervention employing twenty-four 18 to 31-year-old (22.2+/-3.1 years, mean +/- s.d.) overweight women (75.5+/-9.6 kg). TEM and fat oxidation were measured using respiratory gas exchange after a meal challenge, and TEE was measured by doubly labeled water. Fat mass (FM) and lean mass (fat-free mass (FFM)) were measured by dual-energy X-ray absorptiometry. Subjects were randomized into one of these three intervention groups: (i) placebo (<800 mg/day calcium intake); (ii) 900 mg/day calcium supplement; (iii) three servings of dairy products/day to achieve an additional 900 mg/day. There were no group effects observed in change in TEE; however, a group effect was observed for fat oxidation after adjusting for FFM (P=0.02). The treatment effect was due to an increase in fat oxidation in the calcium-supplemented group of 1.5+/-0.6 g/h, P=0.02. Baseline 25-hydroxyvitamin D (25OHD) was positively correlated with TEM (R=0.31, P=0.004), and trended toward a correlation with fat oxidation (P=0.06), independent of group assignment. Finally, the change in log parathyroid hormone (PTH) was positively correlated with the change in trunk FM (R=0.27, P=0.03). These results support that calcium intake increases fat oxidation, but does not change TEE and that adequate vitamin D status may enhance TEM and fat oxidation.

The −3826 A→G Variant of the Uncoupling Protein-1 Gene Diminishes Postprandial Thermogenesis after a High Fat Meal in Healthy Boys

This study investigated whether the -3826 A-->G nucleotide variant of the uncoupling protein-1 (UCP1) gene is correlated with postprandial thermogenesis after a high fat meal in children. Healthy boys, aged 8-11 yr, were examined for resting energy expenditure and the thermic effect of a meal (TEM), which were measured by indirect calorimetry for 180 min after a high fat (70% fat, 20% carbohydrate, and 10% protein, providing 30% of the daily energy requirement) and a high carbohydrate meal (20% fat, 70% carbohydrate, and 10% protein). The sympatho-vagal activities were assessed by means of spectral analysis of the heart rate variability during the same period. Children were genotyped for UCP1 polymorphism by applying a PCR-restriction fragment length polymorphism using buccal samples. There was no reaction of sympathetic activity to the high carbohydrate meal in either the GG allele or the AA+AG group and no significant difference in TEM. However, after the high fat meal, sympathetic responses were found in both groups; further, the GG allele group showed significantly lower TEM than the AA+AG group. In conclusion, despite fat-induced sympathetic stimulation, GG allele carriers have a lowered capacity of TEM in response to fat intake, suggesting that such impaired UCP1-linked thermogenesis can have adverse effects on the regulation of body weight.

Areca nut, energy metabolism and hunger in Asian men

Background : The nut of the Areca catechu palm has long been attributed effects on hunger and the digestive process. Objectives : The objectives were to assess experimentally effects of areca nut on fasting and postprandial energy metabolism, substrate utilization and hunger. Subjects and methods : Two randomized, placebo-controlled, double-blind studies were undertaken. In study 1, eight Indian men received bioadhesive gels delivering 0, 5, 10 or 20 mg arecoline to the buccal sulcus after an overnight fast. Resting energy expenditure and substrate utilization were determined by ventilated hood calorimetry over 6 h during which hunger was rated on five occasions. In study 2, 15 Indian men received gels delivering 0 or 10 mg arecoline after consuming a 2.5 MJ meal, and the same protocol was then applied as in study 1. Results : Fasting resting energy expenditures exceeded basal metabolic rate (BMR) by 5.4 - 0.8% (Mean - SE) after placebo, and 5.1 - 0.7% after 20 mg arecoline, but by 0.9 - 0.8% and 0.7 - 0.5% following 5 mg and 10 mg arecoline, respectively. Carbohydrate (CHO) utilization rates rose after areca nut compared to placebo (F 3,252 = 7.3, p < 0.001). Hunger varied across doses ( h 2 = 10.5, p < 0.02), being lowest after 10 mg and highest after 20 mg, and was influenced by interaction of dose with delta resting energy expenditure. In study 2, areca dose interacted with fat-free mass (FFM) to lower by 5.4 - 11.2% the thermic effect of a meal (F 1,28 = 4.9, p = 0.05), and retarded peak 'digestive-phase' thermogenesis by 60 min (F 1,58 = 5.7, p = 0.02). Postprandial delta CHO utilization was greater (F 1,28 = 4.5, p = 0.05), and hunger was lower ( h : 2 = 3.8, p = 0.05), after areca nut. The areca nut altered relationships of hunger to thermic effects of the meal, and to delta substrate utilization, in ways consistent with appetite suppression. Conclusion : Areca nut constituents modulate metabolic signals regulating appetite in man. This concurs with customary belief.

Pattern and cost of weight gain in previously obese women.

Weight gain is common among postobese individuals, providing an opportunity to address the cost of weight regain on energy expenditure. We investigated the energy cost of weight regain over 1 yr in 28 women [age 39.5 +/- 1.3 (SE) yr; body mass index 24.2 +/- 0.5 kg/m(2)] with recent weight loss (>12 kg). Body composition, total energy expenditure (TEE) using doubly labeled water, resting metabolic rate (RMR), and thermic effect of a meal (TEM) were assessed at 0 and 12 mo. Metabolizable energy intake (MEI) was calculated from TEE and change in body composition. Fourteen women had a weight gain of 13.2 +/- 2.1 kg. Twelve-month cumulative excess MEI, calculated as the intake in excess of TEE at month 0, was 749 +/- 149 MJ. Of this, 462 +/- 83 MJ (62%) were stored as accrued tissue, and 287 +/- 72 MJ (38%) was increased TEE. Expressed per kilogram of body weight gain, the energy cost of weight gain was calculated to be 54.8 +/- 4.6 MJ/kg. Interestingly, weight regain time courses fell into three distinct patterns, possibly requiring varying countermeasures.

Are aerobically fit older individuals more physically active in their free-living time? A doubly labeled water approach.

There is considerable controversy regarding factors regulating free-living physical activity energy expenditure (PAEE) in older individuals. This component is highly variable, is difficult to accurately assess, and reflects both volitional and nonvolitional activities. We examined the association between maximal aerobic fitness (peak VO2) and free-living PAEE in older individuals. One hundred and eighty healthy older patients (96 females and 84 males) between 45-90 yr of age were studied. Total energy expenditure was measured from doubly labeled water. PAEE was calculated as the difference between total energy expenditure, resting metabolic rate, and estimated thermic effect of a meal. Peak VO2 was assessed from an exercise test to volitional fatigue. Fat mass and fat-free mass were assessed from dual energy x-ray absorptiometry. After correction for age, fat mass, and fat-free mass, significant correlations were observed between peak VO2 and PAEE for older males (r = 0.42; P < 0.0001) and females (r = 0.24; P < 0.05), although significant variation among volunteers was noted. When subjects were subdivided by tertiles based on their peak VO2 (liters per min), males with the highest peak VO2 showed greater free-living PAEE than individuals with low peak VO2 (P < 0.01). Similar results were observed in females (P < 0.05). Our results suggest a positive association between higher levels of peak VO2 and greater free-living PAEE in older individuals. This relationship is stronger in older men than in women. These additional energy-dissipating properties during their free-living time may serve to preserve leanness and buffer fat gain with age.

Obesity-related phenotypes and the beta3-adrenoceptor gene variant in postmenopausal women.

We examined the hypothesis that postmenopausal women with the beta3-adrenoceptor gene variant (Trp64Arg) have reduced total daily energy expenditure (TEE), altered free fatty acid kinetics, and increased intra-abdominal fat. A secondary objective was to examine whether the obese state masks the effect of the variant on resting metabolic rate (RMR). There were 23 obese heterozygous women with the genetic variant (age 58 +/- 6 years; BMI 36 +/- 7 kg/m2) who were compared with 19 homozygous obese women with the normal allele (age 56 +/- 4 years; BMI 36 +/- 3 kg/m2). Daily energy expenditure was determined from doubly labeled water and indirect calorimetry, lipolysis from infusion of [1-13C]palmitate, and body fat distribution from computed tomography. No significant differences were found in TEE, RMR, energy expenditure of physical activity, the thermic effect of a meal, fat oxidation as estimated by fasting and postprandial respiratory quotients (RQs), or rate of lipolysis. Similarly, no difference was found in visceral adipose tissue and abdominal subcutaneous fat areas. When RMR was compared between obese (n = 23) and never-obese women with the Trp64Arg variant (n = 16), we found a 317 kcal/day lower RMR in never-obese women after controlling for fat mass, fat-free mass, and age (P < 0.0017). These results do not support the hypothesis that already obese women with the Trp64Arg polymorphism of the beta3-adrenergic receptor gene have lower daily energy expenditure, altered lipolysis, and increased abdominal obesity. On the other hand, the lower RMR in never-obese women suggests that the obese state may mask a moderate effect of the Trp64Arg variant on energy expenditure. Although these results need to be confirmed in other populations, the obese state may have been a confounding factor in previous studies of the beta3-adrenoceptor Trp64Arg variant and energy expenditure.

How much physical activity is needed to minimize weight gain in previously obese women?

Exercise is frequently identified as a predictor of weight maintenance after elective weight loss in retrospective studies of treatments for obesity. We conducted a prospective study to test whether physical activity measured soon after weight loss predicted weight maintenance and to determine how much physical activity was required to optimize maintenance. Thirty-two women [mean (+/- SD) age, 38 +/- 7 y; body mass index (in kg/m2), 24 +/- 3] were recruited through local advertising within 3 mo of reaching their target for weight loss (23 +/- 9 kg). Total energy expenditure (TEE) was measured by the doubly labeled water method. Postabsorptive resting metabolic rate (RMR) and postprandial RMR [expressed as thermic effect of a meal (TEM)] were measured by respiratory gas exchange. Women in the physically active group (ratio of TEE to RMR = 1.89 +/- 0.08) gained 2.5 +/- 3.1 kg during the 12 mo after reaching their target for weight loss, moderately active women (TEE:RMR = 1.64 +/- 0.05) gained 9.9 +/- 10.5 kg, and sedentary women (TEE:RMR = 1.44 +/- 0.08) gained 7.0 +/- 5.9 kg (P < 0.01). Retrospective analyses of weight regain as a function of energy expended in physical activity indicated a threshold for weight maintenance of 47 kJ x kg body wt(-1) x d(-1). This corresponds to an average of 80 min/d of moderate activity or 35 min/d of vigorous activity added to a sedentary lifestyle.

Thermic effect of meal and fat mass in lean and obese men

This study was designed to investigate the eventual impact of fat mass (FM) on the thermic effect of a meal (TEM) in obesity. Eight lean (BMI : 18.3 – 23.9) and eleven obese (BMI : 27.3 – 32.7) men with similar fat free mass (FFM), but very different fat mass participated in the study. Body composition was assessed by bioelectrical impedance analysis (BIA) at 5 kHz and 1 MHz. Metabolic rates were measured by indirect calorimetry before and after a 4055 kJ (969 kcal) mixed meal. Resting metabolic rates (RMR) were not significantly different between the two groups. The RMR was significantly correlated with FFM (Kendall rank correlation coefficient τ = 0.6, p ≤ 0.0001) and FM (τ = 0.47, p < 0.002). As expected, TEM, expressed in absolute values (303.6 vs 515.3 kJ, p ≤ 0.002) or as a percentage of the test meal energy load (7.5% vs 12.8%, p ≤ 0.002), was significantly lower in the obese than in lean men, respectively. At FFM kept constant, TEM was negatively correlated with absolute FM (τ = −0.34, p ≤ 0.02) and percent FM (τ = −0.35, p ≤ 0.02). FM, whatever the way to express it, was negatively correlated with TEM in sedentary young adult lean and obese men.

Energy intake and energy expenditure in the elderly.

This review briefly examines the effects of aging on resting metabolic rate, thermic effect of a meal, and the energy expenditure of physical activity. Thereafter, the effects of advancing age on total daily energy expenditure as assessed from doubly labeled water studies are examined. The paucity of studies in this area and the small sample sizes preclude definitive conclusions regarding daily energy requirements in the elderly. The rationale underlying measurement of daily energy expenditure to determine energy requirements in older individuals is presented. Evidence is provided that older individuals frequently underreport daily energy intake, and this underreporting is more pronounced in older women with higher levels of body fat. The effects of aerobic and resistance training on resting metabolic rate and total daily energy expenditure are then examined. Both forms of training increase resting metabolic rate due to increases in sympathetic nervous system activity. Lastly, procedures to normalize body size dependent data are discussed. © 1996 Wiley-Liss, Inc.

Measurement of Physical Activity Among Black and White Obese Women

Several recent self-reported surveys have suggested that African-American women may engage in less leisure-time physical activity (PA) than whites. Objective measurements of PA have not been performed, however. Therefore, the purpose of this study was to compare the components of energy expenditure, including PA, between black and white obese women. Using the doubly labeled water method, total daily energy expenditure (TDEE), basal metabolic rate (BMR), thermic effect of a meal (TEM), and PA were measured in 14 black and 15 white moderately obese women over 2 weeks. No statistically significant differences were seen between the 2 groups in BMR, TEM or TDEE. Mean PA was significantly (p = 0.05) lower among black women compared to whites when expressed as MJ. d-1 (3.49 vs. 4.30) or kJ.kg-1.d-1 (37.6 vs. 47.7). Our study supports the survey differences seen in PA among black and white women.

Changes in energy expenditure, anthropometry, and energy intake during the course of pregnancy and lactation in well-nourished Indian women

Basal metabolic rate (BMR), thermic effect of a meal (TEM), anthropometry, and dietary intakes were measured in 18 control subjects; 18 pregnant women at 12, 24, and 34 wk gestation; and in 17 of these women at 12 and 24 wk postpartum, to uncover any metabolic economy associated with either pregnancy or lactation. Results indicated that the BMR and TEM were not associated with any energy saving either during pregnancy or lactation. Mean weight gain from 12 wk gestation to term was 11.4 +/- 3.7 kg; mean birth weight of the infants was 3.06 +/- 0.41 kg. Estimated gain in adipose tissue and fat mass were 3.1 +/- 3.6 and 2.5 +/- 2.9 kg, respectively. Energy cost of pregnancy was estimated to be 303 +/- 171 MJ. The cumulative increase in energy intake over the last two trimesters of pregnancy was 290 +/- 280 MJ, meeting a large part of the total estimated cost of pregnancy. Weight gained by infants who were exclusively breast-fed from birth to 12 wk of age was used as a proxy indicator of adequate lactational performance. The extra energy required during lactation appeared to have been met largely by increases in energy intake, rather than by any metabolic economy or increase in fat mobilization.

Effects of aerobic exercise and dietary carbohydrate on energy expenditure and body composition during weight reduction in obese women

To test the benefits of aerobic exercise and dietary carbohydrate during reduced-energy feeding, 23 obese women (44 +/- 4% fat) were randomly assigned to either aerobic exercise (Ex) or no exercise (Nx), and to a low-fat (LF) or low-carbohydrate (LC) reducing diet (5.00 +/- 0.56 MJ/d) for 12 wk. Changes in body composition, postabsorptive resting metabolic rate (RMR), thermic effect of a meal (TEM), and total daily energy expenditure (TDEE) were measured by respiratory gas exchange and doubly labeled water. Significant effects of Ex included a greater loss of fat mass (Ex: -8.8 +/- 2.1 vs Nx: -6.1 +/- 2.3 kg, P = 0.008) and maintenance of TDEE (Ex: +0.07 +/- 1.23 vs Nx: -1.46 +/- 1.04 MJ/d, P = 0.004), due to a difference in physical activity (Ex: +0.75 +/- 1.06 vs Nx: -0.61 +/- 1.03 MJ/d, P = 0.006), which was not attributable solely to the Ex sessions. RMR in both groups decreased comparably (-0.54 MJ/d), and TEM (% of meal) did not change. Diet composition did not significantly influence body composition or energy expenditure changes, but a greater weight loss was observed after the LC than after the LF (-10.6 +/- 2.0 vs -8.1 +/- 3.0 kg, P = 0.037) diet. The addition of aerobic exercise to a low-energy diet was beneficial in the treatment of moderate obesity because of its favorable effects on body composition, physical activity, and TDEE.

Resting metabolic rate and thermic effect of a meal in the follicular and luteal phases of the menstrual cycle in well-nourished Indian women

The resting metabolic rate (RMR) and thermic effect of a standard test meal (TEM) were measured twice each during the follicular and luteal phases (confirmed by plasma concentrations of progesterone and estradiol) of a single menstrual cycle, and once during the follicular phase of the following menstrual cycle, by using indirect calorimetry, in 13 well-nourished Indian women. There was a significant increase in the TEM (P < 0.05) (6.72 +/- 1.57% vs 7.96 +/- 1.48% of the energy content of the test meal for follicular and luteal phases, respectively) of 18.5% during the luteal phase of the menstrual cycle but no significant difference in the RMR or postmeal total energy output (PMTEO). Dietary energy and macronutrient intakes in all subjects in both phases of the menstrual cycle were also similar. The RMR and the PMTEO were also similar when measured in the follicular phase of consecutive menstrual cycles.

No substantial reduction of the thermic effect of a meal during pregnancy in well-nourished Dutch women

To investigate changes in the thermic effect of a meal (TEM) during pregnancy, metabolic rate was measured in the fasting state and during the first 180 min after consumption of a standardized test meal in twenty-seven women before, and in each trimester of pregnancy. Resting metabolic rate (RMR) showed a steady increase over pregnancy: values in weeks 24 and 35 of pregnancy were significantly higher than the prepregnancy baseline (Tukey's studentized range test). The pattern of changes of postprandial metabolic rate (PPMR) was similar to that of RMR. Consequently TEM, calculated as PPMR minus RMR, did not change over pregnancy; mean TEM values (kJ/180 min) before and in weeks 13, 24 and 35 of pregnancy were 117.3 (SD 19.4), 116.4 (SD 23.7), 111.6 (SD 24.4) and 111.5 (SD 26.7) respectively. We consider changes in TEM of less than 15% to be of little importance physiologically. If true changes in TEM over pregnancy are 15% or more we would have had a 90% chance of observing significant changes in TEM in the present study, given the number of subjects and the methods used. Therefore, we conclude that no substantial reduction in TEM occurs during pregnancy.

Resting metabolic rate and thermic effect of a meal in low- and adequate-energy intake male endurance athletes.

The resting metabolic rate (RMR) and thermic effect of a meal (TEM) were determined in 13 low-energy intake (LOW) and 11 adequate-energy intake (ADQ) male endurance athletes. The LOW athletes reported eating 1,490 kcal.day-1 less than the ADQ group, while the activity level of both groups was similar. Despite these differences, both groups had a similar fat-free mass (FFM) and had been weight stable for at least 2 years. The RMR was significantly lower (p < 0.05) in the LOW group compared to the values of the ADQ group (1.19 vs. 1.29 kcal.FFM-1.hr-1, respectively); this difference represents a lower resting expenditure of 158 kcal.day-1. No differences were found in TEM between the two groups. These results suggest that a lower RMR is one mechanism that contributes to weight maintenance in a group of low- versus adequate-energy intake male athletes.