Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 78
Filtrar
1.
Nat Commun ; 13(1): 3994, 2022 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-35810169

RESUMO

Quantum reservoir engineering is a powerful framework for autonomous quantum state preparation and error correction. However, traditional approaches to reservoir engineering are hindered by unavoidable coherent leakage out of the target state, which imposes an inherent trade off between achievable steady-state state fidelity and stabilization rate. In this work we demonstrate a protocol that achieves trade off-free Bell state stabilization in a qutrit-qubit system realized on a circuit-QED platform. We accomplish this by creating a purely dissipative channel for population transfer into the target state, mediated by strong parametric interactions coupling the second-excited state of a superconducting transmon and the engineered bath resonator. Our scheme achieves a state preparation fidelity of 84% with a stabilization time constant of 339 ns, leading to a 54 ns error-time product in a solid-state quantum information platform.

2.
Nature ; 580(7801): 52-55, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32238942

RESUMO

Conservation laws are deeply related to any symmetry present in a physical system1,2. Analogously to electrons in atoms exhibiting spin symmetries3, it is possible to consider neutrons and protons in the atomic nucleus as projections of a single fermion with an isobaric spin (isospin) of t = 1/2 (ref. 4). Every nuclear state is thus characterized by a total isobaric spin T and a projection Tz-two quantities that are largely conserved in nuclear reactions and decays5,6. A mirror symmetry emerges from this isobaric-spin formalism: nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, should have an identical set of states7, including their ground state, labelled by their total angular momentum J and parity π. Here we report evidence of mirror-symmetry violation in bound nuclear ground states within the mirror partners strontium-73 and bromine-73. We find that a J π = 5/2- spin assignment is needed to explain the proton-emission pattern observed from the T = 3/2 isobaric-analogue state in rubidium-73, which is identical to the ground state of strontium-73. Therefore the ground state of strontium-73 must differ from its J π = 1/2- mirror bromine-73. This observation offers insights into charge-symmetry-breaking forces acting in atomic nuclei.

3.
Obes Rev ; 19 Suppl 1: 36-46, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30511511

RESUMO

Obesity is an extremely resilient condition. Weight loss is most challenging, and weight recidivism is rampant. There is accumulating evidence highlighting that energy deficits meant to produce increased mobilization of energy stores trigger a number of somewhat persistent adaptations that together increase the drive to eat and decrease energy output. These adaptations ostensibly enable a context where the likelihood of energy compensation is heightened. In fact, energy compensation is present for both diet and exercise induced energy deficits although at different magnitudes. For the most part, the energy compensation in response to exercise induced energy deficits seems to be larger. Interestingly, energy compensation appears to be greater for longer interventions, an effect independent of whether the energy deficit is induced through diet or exercise. The latter suggests that the increased drive to eat and the reduced energy expenditure that accompany weight loss might be successfully fought off initially. However, with time there seems to be increasing erosion of the behaviours that initially opposed adaptations to weight loss and increased energy compensation progressively sets in. Under such conditions, it would seem prudent to propose weight loss targets that align with a level of behaviour modifications that can be sustained indefinitely.


Assuntos
Dieta , Ingestão de Energia/fisiologia , Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Redução de Peso/fisiologia , Peso Corporal/fisiologia , Dieta Redutora , Humanos , Obesidade/metabolismo
4.
Int J Obes (Lond) ; 42(3): 353-362, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29151592

RESUMO

BACKGROUND/OBJECTIVES: Inter-individual variability in weight loss during obesity treatment is complex and poorly understood. Here we use whole body and tissue approaches to investigate fuel oxidation characteristics in skeletal muscle fibers, cells and distinct circulating protein biomarkers before and after a high fat meal (HFM) challenge in those who lost the most (obese diet-sensitive; ODS) vs the least (obese diet-resistant; ODR) amount of weight in a highly controlled weight management program. SUBJECTS/METHODS: In 20 weight stable-matched ODS and ODR women who previously completed a standardized clinical weight loss program, we analyzed whole-body energetics and metabolic parameters in vastus lateralis biopsies and plasma samples that were obtained in the fasting state and 6 h after a defined HFM, equivalent to 35% of total daily energy requirements. RESULTS: At baseline (fasting) and post-HFM, muscle fatty acid oxidation and maximal oxidative phosphorylation were significantly greater in ODS vs ODR, as was reactive oxygen species emission. Plasma proteomics of 1130 proteins pre and 1, 2, 5 and 6 h after the HFM demonstrated distinct group and interaction differences. Group differences identified S-formyl glutathione hydratase, heat shock 70 kDA protein 1A/B (HSP72), and eukaryotic translation initiation factor 5 (eIF5) to be higher in ODS vs ODR. Group-time differences included aryl hydrocarbon interacting protein (AIP), peptidylpropyl isomerase D (PPID) and tyrosine protein-kinase Fgr, which increased in ODR vs ODS over time. HSP72 levels correlated with muscle oxidation and citrate synthase activity. These proteins circulate in exosomes; exosomes isolated from ODS plasma increased resting, leak and maximal respiration rates in C2C12 myotubes by 58%, 21% and 51%, respectively, vs those isolated from ODR plasma. CONCLUSIONS: Findings demonstrate distinct muscle metabolism and plasma proteomics in fasting and post-HFM states corresponding in diet-sensitive vs diet-resistant obese women.


Assuntos
Proteínas Sanguíneas/metabolismo , Fibras Musculares Esqueléticas/metabolismo , Obesidade , Proteoma/metabolismo , Biomarcadores/sangue , Proteínas Sanguíneas/análise , Estudos de Casos e Controles , Dieta , Exossomos/metabolismo , Feminino , Humanos , Pessoa de Meia-Idade , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiopatologia , Obesidade/sangue , Obesidade/dietoterapia , Obesidade/epidemiologia , Obesidade/metabolismo , Proteoma/análise , Falha de Tratamento
6.
Eur J Clin Nutr ; 71(12): 1471-1472, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28699628

RESUMO

Olfaction can increase the drive to eat and may partially explain the consistent increases in energy intake (EI) following sleep restriction. We investigated the effects of 50% sleep restriction with altered sleep timing on olfactory performance. We also evaluated whether changes (Δ) in olfactory performance were associated with Δ24 h EI. Twelve men and six women (age: 23±4 years; BMI: 23±3 kg/m2) completed three randomized cross-over conditions: habitual sleep duration, 50% sleep restriction with advanced wake-time, and 50% sleep restriction with delayed bedtime. Sleep was measured in-laboratory (polysomnography). Olfactory performance ('sniffin sticks') and 24 h EI (food menu) were evaluated the next day. A trend for a significant condition*sex interaction was noted for threshold-discrimination-identification (TDI) scores (P=0.09); TDI scores were lowest in women and highest in men, following sleep restriction with advanced wake-time. Δolfactory performance were not associated with Δ24 h EI. The impact of sleep restriction on olfactory performance may differ between sexes. Changes in olfactory performance were not associated with changes in 24 h EI. Studies investigating prolonged effects of sleep loss on the relationship between olfactory performance with EI are needed.


Assuntos
Percepção Olfatória , Privação do Sono/fisiopatologia , Sono/fisiologia , Fatores de Tempo , Adulto , Índice de Massa Corporal , Estudos Cross-Over , Dieta , Feminino , Humanos , Masculino , Polissonografia , Tamanho da Amostra , Adulto Jovem
7.
Climacteric ; 19(4): 381-6, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27294579

RESUMO

INTRODUCTION: Conflicting results have been reported concerning the prevalence of cardiometabolic risk factors in women experiencing vasomotor symptoms (VMS). OBJECTIVES: To compare cardiometabolic risk factors between women with and without VMS during the menopause transition and to determine the influence of physical activity on the prevalence of VMS. METHODS: Yearly assessment of women transitioning through menopause included self-reported VMS (hot flushes and night sweats), body composition and fat distribution, fasting glucose, insulin and lipids, and physical activity levels. RESULTS: Eighty-five of the 102 premenopausal women at baseline were included (age: 49.9 ± 2.0 years; body mass index: 23.2 ± 2.2 kg/m(2)). According to linear mixed model analyses, no statistically significant differences were observed for fat mass, lean body mass, body fat distribution indices and cardiometabolic risk factors, when comparing symptomatic vs. asymptomatic women. Neither physical activity levels nor intensity were associated with the prevalence of VMS. CONCLUSION: Our results suggest that women transitioning through menopause who reported VMS did not show greater deteriorations in body composition, body fat distribution and cardiometabolic risk factors. Furthermore, physical activity levels were not associated with lower prevalence of vasomotor symptoms in the present cohort.


Assuntos
Doenças Cardiovasculares/etiologia , Fogachos/etiologia , Menopausa/fisiologia , Sistema Vasomotor/fisiopatologia , Doenças Cardiovasculares/epidemiologia , Exercício Físico/fisiologia , Feminino , Fogachos/epidemiologia , Humanos , Pessoa de Meia-Idade , Prevalência , Fatores de Risco
8.
Climacteric ; 17(4): 449-55, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24559300

RESUMO

OBJECTIVES: It is unknown whether the satiety quotient (SQ) differs across the menopausal transition, and whether changes in SQ are related to changes in anthropometric/body composition variables. The objective of this study was to evaluate the changes in SQ and its association with energy intake and changes in anthropometric/body composition variables across the menopausal transition. METHODS: At baseline, 102 premenopausal women (aged 49.9 ± 1.9 years, body mass index 23.3 ± 2.2 kg/m(2)) took part in a 5-year observational, longitudinal study. Body composition (DXA), appetite (visual analog scales), energy and macronutrient intakes (ad libitum lunch and 7-day food diary) were assessed annually. The SQ (mm/100 kcal) was calculated at 60 and 180 min post-breakfast consumption. RESULTS: Overall, the SQ increased at years 3 and 4 (p = 0.01-0.0001), despite no significant differences between menopausal status groups. Lower fullness, prospective food consumption and mean SQ values predicted overall increases in lunch energy and macronutrient intakes (p = 0.04-0.01), whereas only prospective food consumption and fullness SQ predicted energy intake and carbohydrate intake, respectively, when assessed with food diaries (p = 0.01). Delta SQs were negatively correlated with changes in waist circumference (p = 0.03-0.02), whereas delta SQs were positively (p = 0.04) and negatively (p = 0.02) associated with delta fat mass between years 1 and 5, and years 4 and 5, respectively. CONCLUSION: These results suggest that variations in SQ across the menopausal transition are related to energy and macronutrient intakes and coincide with changes in body composition and waist circumference.


Assuntos
Composição Corporal , Menopausa , Circunferência da Cintura , Antropometria/métodos , Apetite , Índice de Massa Corporal , Canadá , Ingestão de Alimentos/fisiologia , Ingestão de Alimentos/psicologia , Ingestão de Energia/fisiologia , Feminino , Humanos , Estudos Longitudinais , Menopausa/fisiologia , Menopausa/psicologia , Pessoa de Meia-Idade , Saciação
9.
Climacteric ; 17(1): 79-86, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23909399

RESUMO

OBJECTIVE: To investigate the relationship between time spent performing physical activity (PA) and adiposity across the menopausal transition. METHODS: Body weight and body composition were analyzed in 65 women (47-54 years old; body mass index 23.2 ± 2.4 kg/m(2)) in a 5-year prospective study. Time spent in PA of varying intensities (sedentary, light, moderate and vigorous) was determined from 7-day accelerometer measurement and energy intake with a 7-day food diary. RESULTS: Significant negative correlations were observed between the time spent in light-intensity PA and fat mass (FM) (r = -0.38, p < 0.005), central FM (r = -0.36, p < 0.005), peripheral FM (r = -0.33, p < 0.01), and percent body fat (r = -0.42, p < 0.001) at year 1, respectively. No significant correlations were noted between measures of adiposity and time spent performing either moderate or vigorous PA. Analyses using tertiles of time spent in light PA at year 1 showed that FM (20.7 ± 4.0 vs. 20.3 ± 6.6 vs. 16.6 ± 4.6 kg, p < 0.05), central FM (10.1 ± 2.6 vs. 10.0 ± 3.8 vs. 7.8 ± 2.4 kg; p < 0.05) and percent body fat (34.5 ± 5.1 vs. 32.2 ± 7.7 vs. 28.1 ± 6.2%, p < 0.01) were all significantly lower in women in the highest tertile. These differences remained significant after covariate analyses using time spent in moderate- and high-intensity PA and total energy intake. Finally, lower levels of FM, percent body fat, central and peripheral FM persisted in women who spent more time in light PA (highest tertiles) over the 5-year follow-up. CONCLUSION: Our results suggest that the time spent performing light PA may have a greater impact on adiposity than moderate and/or vigorous PA, an observation independent of the menopausal status.


Assuntos
Adiposidade , Exercício Físico , Menopausa/fisiologia , Pré-Menopausa/fisiologia , Composição Corporal , Índice de Massa Corporal , Peso Corporal , Ingestão de Energia , Feminino , Humanos , Pessoa de Meia-Idade , Estudos Prospectivos , Fatores de Tempo
10.
Eur J Clin Nutr ; 68(2): 271-6, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24065065

RESUMO

BACKGROUND/OBJECTIVE: The purpose of this study was to investigate changes in dietary intake and appetite across the menopausal transition. SUBJECTS/METHODS: This was a 5-year observational, longitudinal study on the menopausal transition. The study included 94 premenopausal women at baseline (age: 49.9±1.9 years; BMI: 23.3±2.3 kg/m2). Body composition (dual-energy X-ray absorptiometry), appetite (visual analogue scale), eating frequency, energy intake (EI) and macronutrient composition (7-day food diary and buffet-type meal) were measured annually. RESULTS: Repeated-measures analyses revealed that total EI and carbohydrate intake from food diary decreased significantly over time in women who became postmenopausal by year 5 (P>0.05) compared with women in the menopausal transition. In women who became postmenopausal by year 5, fat and protein intakes decreased across the menopausal transition (0.05>P<0.01). Although a decrease in % fat intake was observed during the menopausal transition (P<0.05), this variable was significantly increased in the postmenopausal years (P<0.05). Spontaneous EI and protein intake also declined over time and were higher in the years preceding menopause onset (P<0.05). Desire to eat, hunger and prospective food consumption increased during the menopausal transition and remained at this higher level in the postmenopausal years (0.05>P<0.001). Fasting fullness decreased across the menopausal transition (P<0.05). CONCLUSION: These results suggest that menopausal transition is accompanied with a decrease in food intake and an increase in appetite.


Assuntos
Apetite/fisiologia , Dieta , Menopausa/fisiologia , Composição Corporal , Índice de Massa Corporal , Carboidratos da Dieta/administração & dosagem , Gorduras na Dieta/administração & dosagem , Proteínas Alimentares/administração & dosagem , Ingestão de Alimentos/fisiologia , Ingestão de Energia , Feminino , Humanos , Estudos Longitudinais , Pessoa de Meia-Idade , Pós-Menopausa/fisiologia
11.
Mol Psychiatry ; 19(7): 823-33, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23958955

RESUMO

3,4-Methylenedioxymethamphetamine (MDMA or 'ecstasy') is a psychostimulant drug, widely used recreationally among young people in Europe and North America. Although its neurotoxicity has been extensively described, little is known about its ability to strengthen neural circuits when administered in a manner that reproduces human abuse (i.e. repeated exposure to a low dose). C57BL/6J mice were repeatedly injected with MDMA (10 mg kg(-1), intraperitoneally) and studied after a 4-day or a 1-month withdrawal. We show, using in vivo microdialysis and locomotor activity monitoring, that repeated injections of MDMA induce a long-term sensitization of noradrenergic and serotonergic neurons, which correlates with behavioral sensitization. The development of this phenomenon, which lasts for at least 1 month after withdrawal, requires repeated stimulation of α(1B)-adrenergic and 5-hydroxytryptamine (5-HT)(2A) receptors. Moreover, behavioral and neuroendocrine assays indicate that hyper-reactivity of noradrenergic and serotonergic networks is associated with a persistent desensitization of somatodendritic α(2A)-adrenergic and 5-HT1A autoreceptor function. Finally, molecular analysis including radiolabeling, western blot and quantitative reverse transcription-polymerase chain reaction reveals that mice repeatedly treated with MDMA exhibit normal α(2A)-adrenergic and 5-HT(1A) receptor binding, but a long-lasting downregulation of Gαi proteins expression in both locus coeruleus and dorsal raphe nucleus. Altogether, our results show that repeated MDMA exposure causes strong neural and behavioral adaptations and that inhibitory feedback mediated by α(2A)-adrenergic and 5-HT(1A) autoreceptors has an important role in the physiopathology of addictive behaviors.


Assuntos
Neurônios Adrenérgicos/efeitos dos fármacos , Alucinógenos/farmacologia , Atividade Motora/efeitos dos fármacos , N-Metil-3,4-Metilenodioxianfetamina/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Neurônios Serotoninérgicos/efeitos dos fármacos , Neurônios Adrenérgicos/metabolismo , Agonistas de Receptores Adrenérgicos alfa 1/farmacologia , Agonistas de Receptores Adrenérgicos alfa 2/farmacologia , Animais , Sensibilização do Sistema Nervoso Central , Núcleo Dorsal da Rafe/efeitos dos fármacos , Núcleo Dorsal da Rafe/metabolismo , Regulação para Baixo/efeitos dos fármacos , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/metabolismo , Locus Cerúleo/efeitos dos fármacos , Locus Cerúleo/metabolismo , Masculino , Camundongos , Receptor 5-HT1A de Serotonina/metabolismo , Receptor 5-HT2A de Serotonina , Receptores Adrenérgicos alfa 2/metabolismo , Neurônios Serotoninérgicos/metabolismo , Agonistas do Receptor 5-HT1 de Serotonina/farmacologia , Agonistas do Receptor 5-HT2 de Serotonina/farmacologia
12.
Eur J Clin Nutr ; 67(12): 1328-30, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24129360

RESUMO

We examined satiety quotient (SQ) and energy intake (EI) according to sleep duration, quality and timing. Seventy-five overweight/obese men (age: 41.1±5.8 years; body mass index: 33.6±2.9 kg/m(2)) completed visual analogue scales for appetite sensations before, immediately after and every 10 minutes for 1 hour following a standardized breakfast. The mean SQ (primary outcome of the study) was calculated from four appetite sensations. The Pittsburgh Sleep Quality Index identified short-duration (<7 h/night) and 'recommended sleep duration' (7 h/night) sleepers, poor (score 5)- and good (score <5)-quality sleepers and late (midpoint of sleep >0230 hours) and early (midpoint of sleep 0230 hours) sleepers. A 3-day food record and buffet-style meal assessed the EI. Short-duration sleepers had a lower mean SQ compared with recommended sleep duration sleepers (6.5±4.9 vs 8.8±4.3 mm/100 kcal; P=0.04). The mean SQ between poor and good (6.9±4.6 vs 8.7±4.6 mm/100 kcal; P=0.11) and that between early and late (8.99±5.10 vs 9.32±4.02 mm/100 kcal; P=0.78) sleepers were not significantly different. EI did not differ between the sleep groups. Thus, short-duration sleepers had a lower mean SQ compared with recommended sleep duration sleepers. However, this did not coincide with an increased EI.


Assuntos
Obesidade/fisiopatologia , Sobrepeso/fisiopatologia , Saciação/fisiologia , Sono/fisiologia , Adulto , Ingestão de Energia , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Tempo
13.
Eur J Clin Nutr ; 67(4): 407-11, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23422924

RESUMO

OBJECTIVES: Factors that influence weight gain during the menopausal transition are not fully understood. The purpose of this study was to investigate changes in energy expenditure (EE) across the menopausal transition. METHODS: In all, 102 premenopausal women (age: 49.9 ± 1.9 years; body mass index: 23.3 ± 2.2 kg/m(2)) were followed for 5 years. Body composition (dual-energy X-ray absorptiometry), physical activity EE (accelerometer), resting EE and thermic effect of food (indirect calorimetry) were measured annually. RESULTS: Total EE decreased significantly over time in postmenopausal women (P<0.05), which was mostly due to a decrease in physical activity EE (P<0.05). Although average resting EE remained stable over time in postmenopausal women, a significant increase, over the 5-year period, was noted in women who were in the menopausal transition by year 5 (P<0.05). Finally, the time spent in moderate physical activity decreased and the time spent in sedentary physical activity increased during the menopausal transition (P<0.05). CONCLUSION: These results suggest that menopausal transition is accompanied with a decline in EE mainly characterized by a decrease in physical activity EE and a shift to a more sedentary lifestyle.


Assuntos
Metabolismo Energético , Menopausa/fisiologia , Absorciometria de Fóton , Metabolismo Basal , Índice de Massa Corporal , Calorimetria Indireta , Ingestão de Energia , Feminino , Seguimentos , Humanos , Pessoa de Meia-Idade , Atividade Motora , Pré-Menopausa/fisiologia , Aumento de Peso
14.
J Physiol Biochem ; 69(3): 497-505, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23355065

RESUMO

This study was performed to examine whether changes in subcutaneous adipose tissue (SCAT) metabolism indices after weight loss were related to the magnitude of weight regain. Nine men and ten premenopausal women whose body mass index ranged from 30 to 42 kg/m(2), 35-48 years old, were studied before and after a 15-week weight loss program, as well as at a 17-22-month follow-up period. Although body composition was evaluated at all study periods, abdominal and femoral SCAT-lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities, and α2- and ß-adrenoceptors (ARs) were measured before and after weight loss, exclusively. Although the SCAT-LPL activity did not change after weight loss in men, it tended to decrease in the femoral depot of women (p = 0.06). SCAT-HSL activity remained unchanged after weight reduction in men, while the post-weight loss lipase activity tended to be higher in both regions of women (p = 0.06). Although the post-weight loss number of ß-ARs was higher irrespective of the fat depot (0.001 < p < 0.05), the number of α2-ARs was increased in the femoral (p < 0.05), but not in the abdominal SCAT (p = 0.08) after weight reduction, in men. Neither the α2- nor the ß-AR density changed after weight reduction, in women. Abdominal SCAT-LPL activity after weight reduction was negatively related to weight regain indices, in women (-0.65 < Rhô < -0.75; 0.01 < p < 0.05). Both the post-weight loss abdominal SCAT α2-AR density and the α2-/ß-AR balance were positively associated with weight regain indices, in men (0.69 < Rhô < 0.88; 0.01 < p < 0.05). These results suggest that selected SCAT metabolism indices could predict failure to weight loss maintenance, in both genders.


Assuntos
Restrição Calórica , Obesidade/dietoterapia , Obesidade/metabolismo , Gordura Subcutânea Abdominal/metabolismo , Abdome/fisiopatologia , Adulto , Biópsia , Composição Corporal , Feminino , Humanos , Lipase Lipoproteica/metabolismo , Masculino , Pessoa de Meia-Idade , Obesidade/fisiopatologia , Receptores Adrenérgicos alfa 2/metabolismo , Receptores Adrenérgicos beta/metabolismo , Fatores Sexuais , Esterol Esterase/metabolismo , Gordura Subcutânea Abdominal/fisiopatologia , Coxa da Perna/fisiopatologia , Aumento de Peso , Redução de Peso
15.
Int J Obes (Lond) ; 37(6): 759-64, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22846776

RESUMO

The decrease in energy expenditure that occurs during weight loss is a process that attenuates over time the impact of a restrictive diet on energy balance up to a point beyond which no further weight loss seems to be possible. For some health professionals, such a diminished energy expenditure is the normal consequence of a progressive decrease in the motivation to exercise over the course of a weight-reducing program. Another explanation of decreased energy needs during weight loss is the decrease in body energy stores (that is, fat mass and muscle mass) and its related obligatory costs of living. Many studies have also documented the existence of adaptive thermogenesis in the context of weight loss, which represents a greater-than-predicted decrease in energy expenditure. In this paper, we pursue the analysis of this phenomenon by demonstrating that an adaptive decrease in thermogenesis can have a major role in the occurrence of resistance to further lose fat in weight-reduced obese individuals. Evidence is also presented to support the idea of greater hunger sensations in individuals displaying more pronounced thermogenic changes. Finally, as the decrease in thermogenesis persists over time, it is also likely associated with a greater predisposition to body-weight regain after weight loss. Globally, these observations suggest that the adaptive reduction in thermogenesis that accompanies a prolonged negative energy balance is a major determinant of the ability to spontaneously lose body fat.


Assuntos
Adaptação Fisiológica , Tecido Adiposo/metabolismo , Metabolismo Energético , Obesidade/metabolismo , Termogênese , Redução de Peso , Regulação do Apetite , Peso Corporal , Ingestão de Energia , Feminino , Humanos , Masculino , Motivação
16.
Obes Rev ; 13(8): 681-91, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22417138

RESUMO

Obesity is characterized by the accumulation of excess body fat and can be conceptualized as the physical manifestation of chronic energy excess. An important challenge of today's world is that our so-called obesogenic environment is conducive to the consumption of energy and unfavourable to the expenditure of energy. The modern, computer-dependent, sleep-deprived, physically inactive humans live chronically stressed in a society of food abundance. From a physiological standpoint, the excess weight gain observed in prone individuals is perceived as a normal consequence to a changed environment rather than a pathological process. In other words, weight gain is a sign of our contemporary way of living or a 'collateral damage' in the physiological struggle against modernity. Additionally, substantial body fat loss can complicate appetite control, decrease energy expenditure to a greater extent than predicted, increase the proneness to hypoglycaemia and its related risk towards depressive symptoms, increase the plasma and tissue levels of persistent organic pollutants that promote hormone disruption and metabolic complications, all of which are adaptations that can increase the risk of weight regain. In contrast, body fat gain generally provides the opposite adaptations, emphasizing that obesity may realistically be perceived as an a priori biological adaptation for most individuals. Accordingly, prevention and treatment strategies for obesity should ideally target the main drivers or root causes of body fat gain in order to be able to improve the health of the population.


Assuntos
Adaptação Fisiológica/fisiologia , Obesidade/prevenção & controle , Obesidade/fisiopatologia , Estresse Fisiológico , Ingestão de Energia/fisiologia , Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Humanos , Obesidade/metabolismo , Comportamento Sedentário , Estresse Psicológico/fisiopatologia , Aumento de Peso
17.
Eur J Clin Nutr ; 65(1): 55-62, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20842172

RESUMO

BACKGROUND/OBJECTIVES: Gut hormones have been shown to influence energy intake (EI). To our knowledge, no study has investigated the effects of dietary patterns aimed at optimizing fullness on EI, appetite and gut hormones. SUBJECT/METHODS: To determine whether individually timing high-protein preloads would impact EI, appetite, and peptide YY and glucagon-like peptide-1 (GLP-1) levels. Ten men (body mass index = 25.5 ± 2.6 kg/m(2)) participated in a randomized crossover trial. The three conditions consisted of the self-selection of snacks (condition 1), or the consumption of a preload (300 kcal: 40% protein, 40% carbohydrates and 20% fat) at either 15 min (condition 2) or ∼ 50 min (individually set) (condition 3) before lunch and dinner. During each condition, a standardized breakfast was served, whereas lunch and dinner were self-selected from a five-item menu, and eaten ad libitum. Mealtime and daily EI were measured. Appetite, peptide YY and GLP-1 were sampled over 9 h. RESULTS: No differences in daily EI were noted across conditions (1 = 3078 ± 720 kcal; 2 = 2929 ± 264 kcal; 3 = 2998 ± 437 kcal; not significant). For the most part, daily profiles as well as premeal levels of peptide YY and GLP-1 were not different between conditions. Desire to eat, hunger and prospective food consumption were found to be lowest during condition 1 (P < 0.05). CONCLUSIONS: According to these results, it would seem that individually timing high-protein preloads does not reduce daily EI in healthy human subjects.


Assuntos
Proteínas Alimentares/administração & dosagem , Proteínas Alimentares/metabolismo , Ingestão de Energia , Peptídeo 1 Semelhante ao Glucagon/sangue , Peptídeo YY/sangue , Adulto , Apetite , Área Sob a Curva , Estudos Cross-Over , Ingestão de Alimentos , Humanos , Masculino , Fatores de Tempo , Adulto Jovem
18.
J Sports Med Phys Fitness ; 50(4): 377-84, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21178922

RESUMO

AIM: The limited potential of exercise to induce weight loss could be partly due to the overestimation of the energy cost of exercise. The objectives of this study were twofold: 1) to investigate whether men and women are able to accurately estimate exercise energy expenditure (EE); and 2) to determine whether they have the ability to accurately compensate for the EE of exercise during a buffet-type meal. METHODS: Sixteen (8 men, 8 women) moderately active (VO2 peak=45.4±7.7 mL.kg-1.min-1), normal weight (BMI=22.8±3.3 kg/m2) individuals, aged 20-35 years, were studied. They were blinded to two randomly assigned experimental conditions: a 200 and a 300 kcal (measured by indirect calorimetry) exercise sessions that were performed on a treadmill at the same intensity (50% of VO2 peak). At the end of each exercise session individuals were asked to estimate EE of the exercise sessions and to then eat the caloric equivalent of their estimated exercise EE from a buffet-type meal. RESULTS: Estimated EE was higher than measured EE for both the 200 kcal (825.0±1061.8 vs. 200.1±0.7 kcal, P<0.05) and 300 kcal (896.9±952.4 vs. 300.2±0.7 kcal, P<0.05) sessions. Further, post-exercise energy intake was higher than measured EE for the 200 kcal (556.8±204.4 vs. 200.1±0.7 kcal, P<0.001) and the 300 kcal (607.2±166.5 vs. 300.2±0.7 kcal, P<0.001) sessions. Although post-exercise energy intake was lower than estimated EE, no significant differences were noted. CONCLUSION: These results suggest that normal weight individuals overestimate EE during exercise by 3-4 folds. Further, when asked to precisely compensate for exercise EE with food intake, the resulting energy intake is still 2 to 3 folds greater than the measured EE of exercise.


Assuntos
Metabolismo Energético , Exercício Físico , Adulto , Calorimetria Indireta , Estudos Cross-Over , Ingestão de Energia , Teste de Esforço , Feminino , Humanos , Masculino , Método Simples-Cego , Adulto Jovem
19.
Int J Obes (Lond) ; 34(9): 1387-95, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20368709

RESUMO

OBJECTIVE: Chronic subclinical inflammation and regular physical activity have opposing relationships to obesity-related metabolic diseases. Yet, the association between chronic inflammation and physical activity has rarely been examined in obese subjects. We examined the association between physical activity energy expenditure (PAEE), total (TEE) and resting energy expenditure (REE) and cardiorespiratory fitness (VO(2)peak) with inflammatory markers in overweight/obese women. DESIGN: Cross-sectional study. METHODS: The study included 152 overweight/obese postmenopausal women who were sedentary and free of chronic/inflammatory diseases (mean age: 57.5 (95% confidence interval (CI) 56.7-58.3) years, body mass index (BMI): 32.5 (95% CI 31.8-33.2) kg m(-2)). The following parameters were measured: TEE (doubly labeled water), REE (indirect calorimetry), PAEE (as (TEE x 0.90)-REE), VO(2)peak (ergocycle) and serum high-sensitive C-reactive protein (hsCRP), haptoglobin, soluble tumor necrosis factor-α receptor 1 (sTNFR1), interleukin-6, orosomucoid and white blood cells. RESULTS: Sedentary women with the highest tertile of PAEE (1276 (1233-1319) kcal day(-1)) had lower concentrations of hsCRP and haptoglobin than those in the lowest tertile (587 (553-621) kcal day(-1)) after adjustment for fat mass (P<0.05). Soluble TNFR1 was positively correlated with VO(2)peak, TEE and REE (P<0.05), and hsCRP and orosomucoid were positively associated with REE (P<0.01), whereas haptoglobin was negatively associated with PAEE (P<0.05). In stepwise regression analyses that examined the concomitant associations of components of energy expenditure with inflammatory markers, PAEE remained the only predictor of hsCRP and haptoglobin (P<0.05), explaining 14 and 5%, respectively, of their variation,whereas REE was the only predictor of orosomucoid (r (2) = 0.05, P = 0.02) after adjustment for fat mass. Adding leptin to the regression models results in similar relationships between inflammatory markers and components of energy expenditure. CONCLUSION: PAEE is an independent predictor of hsCRP and haptoglobin in sedentary overweight/obese postmenopausal women free of chronic disease. Our data support the role of physical activity in reducing subclinical inflammation and risk of metabolic and cardiovascular diseases.


Assuntos
Metabolismo Energético/fisiologia , Mediadores da Inflamação/sangue , Atividade Motora/fisiologia , Obesidade/sangue , Comportamento Sedentário , Metabolismo Basal/fisiologia , Biomarcadores , Índice de Massa Corporal , Proteína C-Reativa/metabolismo , Estudos Transversais , Feminino , Haptoglobinas/metabolismo , Humanos , Pessoa de Meia-Idade , Obesidade/fisiopatologia , Pós-Menopausa
20.
Eur J Clin Nutr ; 64(1): 68-74, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19756035

RESUMO

BACKGROUND/OBJECTIVES: To analyze the anthropometric, metabolic, psychosocial and dietary profiles of underreporters, identified by the doubly labeled water technique, in a well-characterized population of overweight and obese postmenopausal women. SUBJECTS/METHODS: The study population consisted of 87 overweight and obese sedentary postmenopausal women (age: 57.7+/-4.8 years, body mass index: 32.4+/-4.6 kg/m(2)). Subjects were identified as underreporters based on the energy intake to energy expenditure ratio of <0.80. We measured (1) body composition (by dual-energy X-ray absorptiometry), (2) visceral fat (by computed tomography), (3) blood profile, (4) resting blood pressure, (5) peak oxygen consumption (VO(2 peak)), (6) total energy expenditure, (7) muscle strength and (8) psychosocial and dietary profiles. RESULTS: Out of 87 subjects, 50 (57.5%) were identified as underreporting subjects in our cohort. Underreporters showed higher levels of body mass index, fat mass, visceral fat, hsC-reactive protein, perceived stress and percentage of energy from protein, as well as lower levels of VO(2 peak), dietary intake of calcium, fiber, iron, vitamin B-1 and 6, as well as servings of fruit and vegetables. Logistic regression analysis showed that fat mass, odd ratio 1.068 (95% confidence interval 1.009-1.130) and perceived stress, odd ratio 1.084 (95% confidence interval 1.011-1.162) were independent characteristics of underreporters. CONCLUSIONS: Results from this study show significant differences in anthropometric, metabolic, psychosocial and dietary profiles between underreporters and non-underreporters in our cohort of overweight and obese postmenopausal women.


Assuntos
Tecido Adiposo , Índice de Massa Corporal , Dieta , Ingestão de Energia , Obesidade/psicologia , Sobrepeso/psicologia , Autorrevelação , Antropometria , Proteína C-Reativa/metabolismo , Canadá , Metabolismo Energético , Feminino , Frutas , Humanos , Gordura Intra-Abdominal , Modelos Logísticos , Micronutrientes , Pessoa de Meia-Idade , Obesidade/sangue , Razão de Chances , Sobrepeso/sangue , Consumo de Oxigênio , Pós-Menopausa , Comportamento Sedentário , Estresse Psicológico , Verduras , Água
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA