Effects of caffeine on energy metabolism, heart rate, and methylxanthine metabolism in lean and obese women.

The magnitude of coffee-induced thermogenesis and the influence of coffee ingestion on substrate oxidation were investigated in 10 lean and 10 obese women, over two 24-h periods in a respiratory chamber. On one occasion the subjects consumed caffeinated coffee and on the other occasion, decaffeinated coffee. The magnitude of thermogenesis was smaller in obese (4.9 +/- 2.0%) than in lean subjects (7.6 +/- 1.3%). The thermogeneic response to caffeine was prolonged during the night in lean women only. The coffee-induced stimulation of energy expenditure was mediated by a concomitant increase in lipid and carbohydrate oxidation. During the next day, in postabsorptive basal conditions, the thermogenic effect of coffee had vanished, but a significant increase in lipid oxidation was observed in both groups. The magnitude of this effect was, however, blunted in obese women (lipid oxidation increased by 29 and 10% in lean and obese women, respectively). Caffeine increased urinary epinephrine excretion. Whereas urinary caffeine excretion was similar in both groups, obese women excreted more theobromine, theophylline, and paraxanthine than lean women. Despite the high levels of urinary methylxanthine excretion, thermogenesis and lipid oxidation were less stimulated in obese than in lean subjects.

Long-term measurements of energy expenditure in humans using a respiration chamber.

There is a need to measure energy expenditure in man for a period of 24 h or even several days. The respiration chamber offers a unique opportunity to reach this goal. It allows the study of energy and nutrient balance; from the latter, acute changes in body composition can be obtained. The respiration chamber built in Lausanne is an air-tight room (5 m long, 2.5 m wide, and 2.5 m high) which forms an open circuit ventilated indirect calorimeter. The physical activity of the subject inside the chamber is continuously measured using a radar system based on the Doppler effect. Energy expenditure of obese and lean women was continuously measured over 24 h and diet-induced thermogenesis was assessed by using an approach which allows one to subtract the energy expended for physical activity from the total energy expenditure. Expressed in absolute terms, total energy expenditure was more elevated in the obese than in the lean controls. Basal metabolic rate was also higher in the obese than in the controls, but diet-induced thermogenesis was found to be blunted in the obese. In a second study, the effect of changing the carbohydrate/lipid content of the diet on fuel utilization was assessed in young healthy subjects with the respiration chamber. After a 7-day adaptation to a high-carbohydrate low-fat diet, the fuel mixture oxidized matched the change in nutrient intake. A last example of the use of the respiration chamber is the thermogenic response and changes in body composition due to a 7-day overfeeding of carbohydrate. Diet-induced thermogenesis was found to be 27%; on the last day of overfeeding, carbohydrate balance was reached by oxidation of 50% of the carbohydrate intake, the remaining 50% being converted into lipid.

Total energy expenditure and patterns of activity in 8-10-year-old obese and nonobese children.

Total energy expenditure (TEE) and patterns of activity were measured by means of a heart rate (HR)-monitoring method in a group of 8-10-year-old children including 13 obese children (weight, 46 +/- 10 kg; fat mass: 32 +/- 9%) and 16 nonobese children (weight, 31 +/- 5 kg; fat mass, 18 +/- 5%). Time for sleeping was not statistically different in the two groups of children (596 +/- 33 vs. 582 +/- 43 min; p = NS). Obese children spent more time doing sedentary activities (400 +/- 129 vs. 295 +/- 127 min; p < 0.05) and less time in nonsedentary activities (449 +/- 126 vs. 563 +/- 135 min; p < 0.05) than nonobese children. Time spent in moderate or vigorous activity-i.e., time spent at a HR between 50% of the maximal O2 uptake (peak VO2) and 70% peak VO2 (moderate) and at a HR > or = 70% peak VO2 (vigorous)-was not statistically different in obese and nonobese children (88 +/- 69 vs. 52 +/- 35 min and 20 +/- 21 vs. 16 +/- 13 min, respectively; p = NS). TEE was significantly higher in the obese group than in the nonobese group (9.46 +/- 1.40 vs. 7.51 +/- 1.67 MJ/day; p < 0.01). The energy expenditure for physical activity (plus thermogenesis) was significantly higher in the obese children (3.98 +/- 1.30 vs. 2.94 +/- 1.39 MJ/day; p < 0.05). The proportion of TEE daily devoted to physical activity (plus thermogenesis) was not significantly different in the two groups, as shown by the ratio between TEE and the postabsorptive metabolic rate (PMR): 1.72 +/- 0.25 obese vs 1.61 +/- 0.28 non-obese. In conclusion, in free-living conditions obese children have a higher TEE than do nonobese children, despite the greater time devoted to sedentary activities. The higher energy cost to perform weight-bearing activities as well as the higher absolute PMR of obese children help explain this apparent paradox.

Unstable shoes increase energy expenditure of obese patients.

BACKGROUND: Ergonomic unstable shoes, which are widely available to the general population, could increase daily non-exercise activity thermogenesis as the result of increased muscular involvement. We compared the energy expenditure of obese patients during standing and walking with conventional flat-bottomed shoes versus unstable shoes.¦METHODS: Twenty-nine obese patients were asked to stand quietly and to walk at their preferred walking speed while wearing unstable or conventional shoes. The main outcome measures were metabolic rate of standing and gross and net energy cost of walking, as assessed with indirect calorimetry.¦RESULTS: Metabolic rate of standing was higher while wearing unstable shoes compared with conventional shoes (1.11±0.20 W/kg(-1)vs 1.06±0.23 W/kg(-1), P=.0098). Gross and net energy cost of walking were higher while wearing unstable shoes compared with conventional shoes (gross: 4.20±0.42 J/kg(-1)/m(-1)vs 4.01±0.39 J/kg(-1)/m(-1), P=.0035; net: 3.37±0.41 J/kg(-1)/m(-1)vs 3.21±0.37 J/kg(-1)/m(-1); P=.032).¦CONCLUSION: In obese patients, it is possible to increase energy expenditure of standing and walking by means of ergonomic unstable footwear. Long-term use of unstable shoes may eventually prevent a positive energy balance.

Métabolisme énergétique de la femme enceinte [Energy metabolism in the pregnant woman].

The maternal and foetal anabolic phase characterizing pregnancy requires energy storage and hence a state of positive energy balance. Dietary surveys, however, have shown an increase in energy intake during pregnancy of small magnitude only. Furthermore, indirect calorimetry measurements indicate an elevation of basal or resting energy expenditure (EE), particularly during the 3rd trimester of pregnancy. These results are confirmed by measurements performed in a respiration chamber which showed that the rate of 24 hours EE of pregnant women is significantly more elevated in the 3rd trimester than in the nonpregnant state; the latter is explained by a rise of basal EE and to a smaller extent by an increase in energy cost of moving around as a result of the greater body weight. In contrast, when the results are expressed per unit body weight, the difference in 24 hours EE observed during pregnancy disappeared. It seems that energy sparing mechanisms-which are still largely unknown-may come into play during this period: postprandial thermogenesis appears to be blunted during pregnancy. This indicates an increase in net efficiency of food energy utilization. The degree of adaptation of physical activity-which has not been previously investigated-remains a research topic of great interest for the future.

The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysis.

Different outcomes of the effect of catechin-caffeine mixtures and caffeine-only supplementation on energy expenditure and fat oxidation have been reported in short-term studies. Therefore, a meta-analysis was conducted to elucidate whether catechin-caffeine mixtures and caffeine-only supplementation indeed increase thermogenesis and fat oxidation. First, English-language studies measuring daily energy expenditure and fat oxidation by means of respiration chambers after catechin-caffeine mixtures and caffeine-only supplementation were identified through PubMed. Six articles encompassing a total of 18 different conditions fitted the inclusion criteria. Second, results were aggregated using random/mixed-effects models and expressed in terms of the mean difference in 24 h energy expenditure and fat oxidation between the treatment and placebo conditions. Finally, the influence of moderators such as BMI and dosage on the results was examined as well. The catechin-caffeine mixtures and caffeine-only supplementation increased energy expenditure significantly over 24 h (428.0 kJ (4.7%); P < 0.001 and 429.1 kJ (4.8%); P < 0.001, respectively). However, 24 h fat oxidation was only increased by catechin-caffeine mixtures (12.2 g (16.0%); P < 0.02 and 9.5 g (12.4%); P = 0.11, respectively). A dose-response effect on 24 h energy expenditure and fat oxidation occurred with a mean increase of 0.53 kJ mg(-1) (P < 0.01) and 0.02 g mg(-1) (P < 0.05) for catechin-caffeine mixtures and 0.44 kJ mg(-1) (P < 0.001) and 0.01 g mg(-1) (P < 0.05) for caffeine-only. In conclusion, catechin-caffeine mixtures or a caffeine-only supplementation stimulates daily energy expenditure dose-dependently by 0.4-0.5 kJ mg(-1) administered. Compared with placebo, daily fat-oxidation was only significantly increased after catechin-caffeine mixtures ingestion.

Lack of thermogenic response to glucose/insulin infusion in diabetic obese subjects.

The change in energy expenditure consecutive to the infusion of glucose/insulin was examined in 17 non-obese (ten young, seven middle-aged) and 27 diabetic and non-diabetic obese subjects by employing the euglycemic insulin clamp technique in conjunction with continuous indirect calorimetry. The obese subjects were divided into four groups according to their response to a 100-g oral glucose test: group A, normal glucose tolerance; group B, impaired glucose tolerance; group C, diabetes with increased insulin response; group D, diabetes with reduced insulin response. The glucose/insulin infusion provoked an increase in energy expenditure in both young and middle-aged controls (+8.2 +/- 1.3 percent and +5.9 +/- 0.5 percent over the preinfusion baseline respectively), but a lower increase in the non-diabetic obese groups A and B (+4.0 +/- 0.7 percent and +2.0 +/- 1.0 percent over the preinfusion baseline respectively, P less than 0.05 and P less than 0.01 vs young controls). However, in the diabetic obese groups C and D, energy expenditure failed to increase in response to the glucose/insulin infusion (mean change: +0.1 +/- 1.0 percent and -2.0 +/- 1.9 percent (P less than 0.01, vs middle-aged) over the preinfusion baseline respectively). When the glucose-induced thermogenesis (GIT) was related to the glucose uptake--taking into account the hepatic glucose production--the GIT was found to be similarly reduced in the diabetics groups (C and D). The net change in the rate of energy expenditure was found to be significantly correlated with the rate of glucose uptake (r = +0.647, n = 44, P less than 0.001) when all the individuals were pooled. In conclusion, this study shows that the low glucose-induced thermogenesis in obese diabetics during glucose insulin infusion is mainly related to a reduced rate of glucose uptake; in addition, inhibition of gluconeogenesis by the glucose/insulin infusion may also contribute to decrease the thermogenic response.

Unstable shoes increase energy expenditure of obese patients.

BACKGROUND: Ergonomic unstable shoes, which are widely available to the general population, could increase daily non-exercise activity thermogenesis as the result of increased muscular involvement. We compared the energy expenditure of obese patients during standing and walking with conventional flat-bottomed shoes versus unstable shoes. METHODS: Twenty-nine obese patients were asked to stand quietly and to walk at their preferred walking speed while wearing unstable or conventional shoes. The main outcome measures were metabolic rate of standing and gross and net energy cost of walking, as assessed with indirect calorimetry. RESULTS: Metabolic rate of standing was higher while wearing unstable shoes compared with conventional shoes (1.11 ± 0.20 W/kg(-1) vs 1.06 ± 0.23 W/kg(-1), P=.0098). Gross and net energy cost of walking were higher while wearing unstable shoes compared with conventional shoes (gross: 4.20 ± 0.42 J/kg(-1)/m(-1)vs 4.01 ± 0.39 J/kg(-1)/m(-1), P=.0035; net: 3.37 ± 0.41 J/kg(-1)/m(-1) vs 3.21 ± 0.37 J/kg(-1)/m(-1); P=.032). CONCLUSION: In obese patients, it is possible to increase energy expenditure of standing and walking by means of ergonomic unstable footwear. Long-term use of unstable shoes may eventually prevent a positive energy balance.

Comparative winter thermoregulation and body temperature in three sympatric Apodemus species (A-alpicola, A-flavicollis, and A-sylvaticus)

When living in sympatry with Apodemus sylvaticus and A. flavicollis, A. alpicola dominates numerically at higher altitudes. A more efficient winter thermal isolation or a higher winter thermogenic capacity procuring a physiological advantage could explain at least part of this domination. We therefore measured body temperature (Tb), oxygen consumption (VO2), wet minimal thermal conductance (C) and non shivering thermogenesis (NST) at different ambient temperatures (Ta) on winter acclimated mice of the three species, and this for the first time in A. alpicola. NST was high and C low in the three species. No significant difference could be noticed either in Tb between 5 and -10 degrees C, in VO2 measurements at a Ta of -10 degrees C or in C. The NST measurements represent, respectively, 135.2% for A. sylvaticus, 142.8% for A. flavicollis and 140.5% for A. alpicola of the expected values, the values for A. sylvaticus being significantly lower than for the other two species. The basal metabolic rates (BMR) represent 169.4% for A. sylvaticus, 161.6% for A. flavicollis and 138.3% for A. alpicola of the expected values. Having removed the effect of body weight, the BMR value was significantly lower in A. alpicola than in A. flavicollis, but no difference could be noticed between A. sylvaticus and the other two species. In conclusion, the three species of mice have very similar acclimated thermoregulatory characteristics, well adapted to cold ambient conditions. One discriminating and advantageous factor could be the lower basal metabolic rate measured in A. alpicola compared to the other two species.

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.

Enteral versus parenteral nutrition: comparison of energy metabolism in lean and moderately obese women.

Continuous respiratory-exchange measurements were performed on ten moderately obese and ten lean young women for 1 h before, 3 h during, and 3 h after either parenteral (IV) or intragastric (IG) administration of a nutrient mixture infused at twice the postabsorptive, resting energy expenditure (REE). REE rose significantly from 0.98 +/- 0.02 to 1.13 +/- 0.03 kcal/min (IV) and from 0.99 +/- 0.02 to 1.13 +/- 0.02 kcal/min (IG) in the lean group; from 1.10 +/- 0.02 to 1.27 +/- 0.03 kcal/min (IV) and from 1.11 +/- 0.02 to 1.29 +/- 0.03 (IG) in the obese group. These increases resulted in similar nutrient-induced thermogenesis of 10.0 +/- 0.7% (IV) and 9.3 +/- 0.9% (IG) in the lean group; of 9.2 +/- 0.7% (IV) and 10.1 +/- 0.8% (IG) in the obese. Nutrient utilization was comparable in both groups and in both routes of administration, although the response time to IG feeding was delayed. These results showed no significant difference in both the thermogenic response and nutrient utilization between moderately obese and control groups using acute IV or IG feeding.

Automatic recognition of postural allocations.

A significant part of daily energy expenditure may be attributed to non-exercise activity thermogenesis and exercise activity thermogenesis. Automatic recognition of postural allocations such as standing or sitting can be used in behavioral modification programs aimed at minimizing static postures. In this paper we propose a shoe-based device and related pattern recognition methodology for recognition of postural allocations. Inexpensive technology allows implementation of this methodology as a part of footwear. The experimental results suggest high efficiency and reliability of the proposed approach.

Continuous versus single bolus enteral nutrition: comparison of energy metabolism in humans.

Continuous respiratory exchange measurements were performed on five women and five men for 1 h before and 6 h after the administration of a milkshake (53% carbohydrates, 30% lipid, and 17% protein energy) given either as a single bolus dose or continuously during 3 h using a nasogastric tube. The energy administered corresponded to 2.3 times the postabsorptive resting energy expenditure. Resting energy expenditure, respiratory quotient, plasma glucose, and insulin concentrations increased sooner and steeper, and plasma free fatty acids levels decreased earlier with the meal ingested as a single dose than with continuous administration. The magnitude of nutrient-induced thermogenesis was greater (P less than 0.01) with the single dose (means +/- SE, 10.0 +/- 0.6%) than with the continuous administration (8.1 +/- 0.5%). The overall (6 h) substrate balances were not significantly different between the two modes of administration. It is concluded that the mode of enteral nutrient administration influences the immediate thermogenic response as well as changes in respiratory quotient, glycemia, and insulinemia; however, the overall nutrient balance was not affected by the mode of enteral nutrient administration.

New evidence for a thermogenic defect in human obesity.

A reduced thermogenic response to food ingestion may contribute to the dynamic phase of weight gain in obesity. A defect in diet-induced thermogenesis has been reported in about one third of an unselected group of obese women. After inducing weight loss with a hypocaloric diet, the thermogenic defect does not disappear. Since basal metabolic rate decreases with weight loss, the overall postprandial energy expenditure of 'post-obese' individuals can be lower than that of lean controls. As a consequence, post-obese subjects must reset energy intake to a lower level than the previous maintenance food consumption in order to avoid relapse of body weight gain.

Predicted effects of small decreases in energy expenditure on weight gain in adult women.

Small daily positive energy imbalances of 200 to 800 kJ (about 50 to 200 kcal) due to reduced resting energy expenditure (REE), reduced diet-induced thermogenesis, or physical inactivity are believed to predispose to obesity. However, estimates of the magnitude of the weight gain often fail to account for concurrent changes in body composition and increases in maintenance energy requirements as weight increases and energy equilibrium is re-established. Using previously reported data on body composition and REE in women and the energy cost of tissue deposition, we used mathematical models to predict the theoretical effect of a persistent reduction in energy expenditure on long-term weight gain, assuming no adaptation in energy intake. The analyses indicate the following effects of a reduced level of energy expenditure in lean and obese women: (i) REE rises more slowly with increasing degrees of obesity due to a declining proportion of the more metabolically active fat-free mass; so, for the same positive energy balance, a significantly greater weight gain is expected for obese than for lean women before energy equilibrium is re-established; (ii) due to the greater energy density of adipose tissue, the time course of weight gain to achieve energy balance is longer for obese subjects: in general, this is approximately five years for lean and ten years for obese women; (iii) the magnitude of weight gain of lean women in response to a reduced energy expenditure of 200 to 800 kJ/day is only about 3 to 15 kg, amounts insufficient to explain severe obesity.