Rôle de l'inactivité physique dans l'étiologie de l'obésité [The role of physical inactivity in the etiology of obesity].

The activity-related energy expenditure mainly depends upon body weight, the type, intensity and duration of the exercise as well as the mechanical efficiency with which the subjects perform the work. Controversy still exist about the role of hypoactivity in the aetiology of obesity both in adolescence and adulthood. A number of experimental studies based on indirect assessment of physical activity (such as pedometers, accelerometers, cinematography and heart rate) have demonstrated a significant reduction in spontaneous physical activity in certain obese groups as compared to lean matched controls. On the other hand, direct measurements of energy expenditure (by indirect calorimetry) have shown a linear relationship between body weight and 24-hour (or activity-related) energy expenditure. It therefore appears that despite the greater placidity characterising some grossly obese subjects, the absolute rate of energy expenditure - particularly in weight bearing activities - is not lower than in lean subjects, since the hypoactivity does not fully compensate for the greater gross energy cost of a given activity.

Energy balance in elderly patients after surgery for a femoral neck fracture.

To study energy and protein balances in elderly patients after surgery, spontaneous energy and protein intake and resting energy expenditure (REE) were measured in 20 elderly female patients with a femoral neck fracture (mean age 81 +/- 4, SD, range 74-87 years; weight 53 +/- 8, range 42-68 kg) during a 5-6 day period following surgery. REE, measured over 20-40 min by indirect calorimetry using a ventilated canopy, averaged 0.98 +/- 0.15 kcal/min on day 3 and decreased to 0.93 +/- 0.15 kcal/min on day 8-9 postsurgery (p less than 0.02). REE was positively correlated with body weight (r = 0.69, p less than 0.005). Mean REE extrapolated to 24 hr (24-REE) was 1283 +/- 194 kcal/day. Mean daily food energy intake measured over the 5-day follow-up period was 1097 +/- 333 kcal/day and was positively correlated with 24-REE (r = 0.50, p less than 0.05). Daily energy balance was -235 +/- 351 kcal/day on day 3 (p less than 0.01 vs zero) and -13 +/- 392 kcal/day on day 8-9 postsurgery (NS vs zero) with a mean over the study period of -185 +/- 289 kcal/day (p less than 0.01 vs zero). When an extra 100 kcal/day was allowed for the energy cost of physical activity, mean daily energy balance over the 5-day study period was calculated to be -285 +/- 289 kcal/day (p less than 0.01 vs zero). Measurements of total 24-hr urinary nitrogen (N) excretion were obtained in a subgroup of 14 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A 600 kb deletion syndrome at 16p11.2 leads to energy imbalance and neuropsychiatric disorders.

BACKGROUND: The recurrent ~600 kb 16p11.2 BP4-BP5 deletion is among the most frequent known genetic aetiologies of autism spectrum disorder (ASD) and related neurodevelopmental disorders. OBJECTIVE: To define the medical, neuropsychological, and behavioural phenotypes in carriers of this deletion. METHODS: We collected clinical data on 285 deletion carriers and performed detailed evaluations on 72 carriers and 68 intrafamilial non-carrier controls. RESULTS: When compared to intrafamilial controls, full scale intelligence quotient (FSIQ) is two standard deviations lower in carriers, and there is no difference between carriers referred for neurodevelopmental disorders and carriers identified through cascade family testing. Verbal IQ (mean 74) is lower than non-verbal IQ (mean 83) and a majority of carriers require speech therapy. Over 80% of individuals exhibit psychiatric disorders including ASD, which is present in 15% of the paediatric carriers. Increase in head circumference (HC) during infancy is similar to the HC and brain growth patterns observed in idiopathic ASD. Obesity, a major comorbidity present in 50% of the carriers by the age of 7 years, does not correlate with FSIQ or any behavioural trait. Seizures are present in 24% of carriers and occur independently of other symptoms. Malformations are infrequently found, confirming only a few of the previously reported associations. CONCLUSIONS: The 16p11.2 deletion impacts in a quantitative and independent manner FSIQ, behaviour and body mass index, possibly through direct influences on neural circuitry. Although non-specific, these features are clinically significant and reproducible. Lastly, this study demonstrates the necessity of studying large patient cohorts ascertained through multiple methods to characterise the clinical consequences of rare variants involved in common diseases.

Gut-derived signaling molecules and vagal afferents in the control of glucose and energy homeostasis.

PURPOSE OF REVIEW: The control of glucose and energy homeostasis, including feeding behaviour, is tightly regulated by gut-derived peptidic and nonpeptidic endocrine mediators, autonomic nervous signals, as well as nutrients such as glucose. We will review recent findings on the role of the gastrointestinal tract innervation and of portal vein glucose sensors; we will review selected data on the action of gastrointestinally released hormones. RECENT FINDINGS: The involvement of mechanosensory vagal afferents in postprandial meal termination has been clarified using mouse models with selective impairments of genes required for development of mechanosensory fibres. These activate central glucogen-like peptide-1/glucogen-like peptide-2 containing ascending pathways linking the visceroceptive brainstem neurons to hypothalamic nuclei. Mucosal terminals comprise the chemosensory vagal afferents responsive to postprandially released gastrointestinal hormones. The mechanism by which the hepatoportal glucose sensor stimulates glucose utilization by muscles was demonstrated, using genetically modified mice, to be insulin-independent but to require GLUT4 and AMP-kinase. This sensor is a key site of glucogen-like peptide-1 action and plays a critical role in triggering first phase insulin secretion. PeptideYY and ghrelin target intracerebral receptors as they are bidirectionally transported across the blood brain barrier. The anorectic functions of peripherally released peptideYY may however be mediated both via vagal afferents and intracerebral Y2 receptors in the brainstem and arcuate nucleus. SUMMARY: These recent findings demonstrate that the use of improved anatomical and physiological techniques and animal models with targeted gene modifications lead to an improved understanding of the complex role of gastrointestinal signals in the control of energy homeostasis.

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.

Assessment of total energy expenditure in free-living patients with cystic fibrosis.

The increase in resting energy expenditure (REE) reported in patients with cystic fibrosis (CF) does not necessarily imply an increase in total energy expenditure (TEE). In this study REE was assessed with open-circuit indirect calorimetry, and free-living 24-hour TEE with the heart rate method. Thirteen patients with CF, aged 8 to 24 years, with adequate nutritional status and moderately decreased pulmonary function, were studied. They were compared with 13 healthy control subjects matched for gender, age, height, and nutritional status. Resting energy expenditure was higher in patients with CF (1512 +/- 88 kcal/day) than in control subjects (1339 +/- 76 kcal/day; p less than 0.01), whereas free-living 24-hour TEE (2345 +/- 127 kcal/day and 2358 +/- 256 kcal/day, respectively) and net mechanical work efficiency of walking on a treadmill (20.4 +/- 0.7% and 19.8 +/- 0.6%, respectively) were similar. Respiratory quotient was higher in patients with CF than in control subjects at rest (0.834 +/- 0.009 vs 0.797 +/- 0.008; p less than 0.05), and tended to remain so during physical exercise, indicating a higher contribution of carbohydrate oxidation to energy expenditure. We conclude that in free living conditions, patients with CF can compensate for their increase in REE by a reduction in spontaneous physical activities or other yet undefined mechanisms.

The role of energy and nutritional support in the intensive care unit.

Malnutrition is common in critically ill, hospitalized patients and so represents a major problem for intensive care. Nutritional support can be beneficial in such cases and may help preserve vital organ and immune function. Energy requirements, route of delivery and potential complications of nutritional support are discussed in this paper.

Twenty-four-hour energy expenditure in pregnant and nonpregnant Gambian women, measured in a whole-body indirect calorimeter.

Twenty-four-hour energy expenditure (EE), daily and sleeping EE, and the energy cost of a standardized treadmill exercise were assessed in a respiration chamber in 41 young pregnant Gambian women at 12 (n = 11), 24 (n = 15), and 36 (n = 15) wk of gestation and compared with 13 nonpregnant nonlactating (NPNL) control women. The rate of 24-h EE was significantly higher (P less than 0.001) at 36 wk gestation (8443 +/- 243 kJ/d) than in the NPNL group (6971 +/- 172 kJ/d) or at 12 and 24 wk (7088 +/- 222 and 7188 +/- 192 kJ/d, respectively). Per unit body weight, no more differences in 24-h EE, daily and sleeping EE, or energy cost of walking were observed between pregnant and NPNL women. There was no statistical difference in the 24-h respiratory quotient among the groups. We conclude that the state of pregnancy in Gambian women induces a progressive rise in 24-h EE, which becomes significant in the third trimester and is proportional to body weight.

Evaluation of organ-specific peripheral doses after 2-dimensional, 3-dimensional and hybrid intensity modulated radiation therapy for breast cancer based on Monte Carlo and convolution/superposition algorithms: implications for secondary cancer risk assessment.

To make a comprehensive evaluation of organ-specific out-of-field doses using Monte Carlo (MC) simulations for different breast cancer irradiation techniques and to compare results with a commercial treatment planning system (TPS). Three breast radiotherapy techniques using 6MV tangential photon beams were compared: (a) 2DRT (open rectangular fields), (b) 3DCRT (conformal wedged fields), and (c) hybrid IMRT (open conformal+modulated fields). Over 35 organs were contoured in a whole-body CT scan and organ-specific dose distributions were determined with MC and the TPS. Large differences in out-of-field doses were observed between MC and TPS calculations, even for organs close to the target volume such as the heart, the lungs and the contralateral breast (up to 70% difference). MC simulations showed that a large fraction of the out-of-field dose comes from the out-of-field head scatter fluence (>40%) which is not adequately modeled by the TPS. Based on MC simulations, the 3DCRT technique using external wedges yielded significantly higher doses (up to a factor 4-5 in the pelvis) than the 2DRT and the hybrid IMRT techniques which yielded similar out-of-field doses. In sharp contrast to popular belief, the IMRT technique investigated here does not increase the out-of-field dose compared to conventional techniques and may offer the most optimal plan. The 3DCRT technique with external wedges yields the largest out-of-field doses. For accurate out-of-field dose assessment, a commercial TPS should not be used, even for organs near the target volume (contralateral breast, lungs, heart).

Elevated energy expenditure and reduced energy intake in obese prepubertal children: paradox of poor dietary reliability in obesity?

The purpose of this study was to assess the validity of two common methods used to assess energy intake. A 3-day weighed dietary record and a dietary history were collected and compared with the total daily energy expenditure (TEE) assessed by the heart rate method in a group of 12 obese and 12 nonobese prepubertal children (mean age 9.3 +/- 1.1 years vs 9.3 +/- 0.4 years). The TEE value was higher in obese than in nonobese children (9.89 +/- 1.08 vs 8.13 +/- 1.39 MJ/day; p < 0.01). Energy intake assessed by the dietary record was significantly lower than TEE in the obese children (7.06 +/- 0.98 MJ/day; p < 0.001) but comparable to TEE in the nonobese children (8.03 +/- 0.99 MJ/day; p = not significant). Energy intake assessed by diet history was lower than TEE in the obese children (8.37 +/- 1.35 MJ/day, p < 0.05) but close to TEE in the nonobese children (8.64 +/- 1.54 MJ/day, p = not significant). These results suggest that obese children underreport food intake and that the dietary record and the diet history are not valid means of assessing energy intake in obese prepubertal children.

Effect of malaria and fever on energy metabolism in Gambian children.

The aim of the present study was to measure the changes in resting energy expenditure (REE) induced by malaria and to assess to what extent they are related to fever and nutritional status. The REE of 19 Gambian children (mean age +/- SEM, 9 +/- 1 y; weight, 24 +/- 2 kg; expected weight for height 86 +/- 1%) were measured with a hood system at repeated intervals at the onset of malaria crisis (test A), 3 to 4 d after therapy (test B), and 14 to 21 d later (test C). Axillary temperature averaged 39.2 +/- 0.1, 36.6 +/- 0.1, and 36.7 +/- 0.1 degrees C in the tests A, B, and C, respectively. REE in test A was significantly higher than REE in test B (223 +/- 10 versus 174 +/- 8 kJ/kg.d, p less than 0.0001), but in test C (169 +/- 8 kJ/kg.d), it did not differ from that observed in test B. The percentage of increase in REE was significantly correlated with the difference in axillary temperature (r = 0.46, p less than 0.05); the slope of the regression line indicated an increase of 6.9% in REE/degree C of fever. Furthermore, the individual increase in REE/degree C was correlated to the percentage of weight for height of the children (r = 0.54, p less than 0.05), indicating that the child's nutritional status influences the magnitude of the hypermetabolism due to fever. We concluded that Gambian children suffering from an acute episode of malaria have an increase in REE averaging 30%; however, REE promptly returns to baseline value a few days after the beginning of therapy.

Negative impact of hypocaloric feeding and energy balance on clinical outcome in ICU patients.

BACKGROUND AND AIMS: Critically ill patients with complicated evolution are frequently hypermetabolic, catabolic, and at risk of underfeeding. The study aimed at assessing the relationship between energy balance and outcome in critically ill patients. METHODS: Prospective observational study conducted in consecutive patients staying > or = 5 days in the surgical ICU of a University hospital. Demographic data, time to feeding, route, energy delivery, and outcome were recorded. Energy balance was calculated as energy delivery minus target. Data in means+/-SD, linear regressions between energy balance and outcome variables. RESULTS: Forty eight patients aged 57+/-16 years were investigated; complete data are available in 669 days. Mechanical ventilation lasted 11+/-8 days, ICU stay 15+/-9 was days, and 30-days mortality was 38%. Time to feeding was 3.1+/-2.2 days. Enteral nutrition was the most frequent route with 433 days. Mean daily energy delivery was 1090+/-930 kcal. Combining enteral and parenteral nutrition achieved highest energy delivery. Cumulated energy balance was between -12,600+/-10,520 kcal, and correlated with complications (P < 0.001), already after 1 week. CONCLUSION: Negative energy balances were correlated with increasing number of complications, particularly infections. Energy debt appears as a promising tool for nutritional follow-up, which should be further tested. Delaying initiation of nutritional support exposes the patients to energy deficits that cannot be compensated later on.