Heloisa Guarita Padilha

Hormonal appetite control is altered by shift work: a preliminary study

Shift work has been associated with a higher propensity for developing nutritional problems and obesity. However, the possible changes in leptin and ghrelin (2 hormones that contribute importantly to the central regulation of food intake) concentrations in this population are poorly described. The objective of the study was to evaluate the daily concentrations of leptin, nonacylated ghrelin, and acylated ghrelin and the appetite ratings in men working different shift schedules. Daily concentrations of nonacylated ghrelin, acylated ghrelin, and leptin and appetite were measured in 3 groups of subjects: workers on fixed night shifts (n = 9), fixed early morning shifts (n = 6), and fixed day shifts (n = 7). Appetite was evaluated by a validated questionnaire. Blood samples were collected every 4 hours over the course of 24 hours for a total of 6 samples. When comparing the 3 groups, leptin concentrations at 8:00 am and 4:00 pm for those workers on the day shift were significantly lower than for those on the early morning shift; and concentrations at noon for those workers on the day shift were significantly lower than for those on the night shift. Nonacylated and acylated ghrelin concentrations were significantly lower for those workers on the early morning shift than for those on the day shift. In general, appetite was the lowest in those working the early morning shift. Shift workers on the early morning shift have lower appetites and concentrations of leptin and nonacylated and acylated ghrelin than the workers on other shifts. Further studies are required to better understand the detailed needs of these individuals.

The influence of sleep and sleep loss upon food intake and metabolism

The present review investigates the role of sleep and its alteration in triggering metabolic disorders. The reduction of the amount of time sleeping has become an endemic condition in modern society and the current literature has found important associations between sleep loss and alterations in nutritional and metabolic aspects. Studies suggest that individuals who sleep less have a higher probability of becoming obese. It can be related to the increase of ghrelin and decrease of leptin levels, generating an increase of appetite and hunger. Sleep loss has been closely associated with problems in glucose metabolism and a higher risk for the development of insulin resistance and diabetes, and this disturbance may reflect decreased efficacy of the negative-feedback regulation of the hypothalamic-pituitary-adrenal axis. The period of sleep is also associated with an increase of blood lipid concentrations, which can be intensified under conditions of reduced sleep time, leading to disorders in fat metabolism. Based on a review of the literature, we conclude that sleep loss represents an important risk factor for weight gain, insulin resistance, type 2 diabetes and dyslipidaemia. Therefore, an adequate sleep pattern is fundamental for the nutritional balance of the body and should be encouraged by professionals in the area.

Relação entre sono e obesidade: uma revisão da literatura

ABSTRACT Relation Between Sleep and Obesity: A Literature Review.Reduction in sleep time has become an endemic condition in modern soci-ety and current literature has found important epidemiological associa-tions between damage in the habitual standard of sleep and obesity. Onthis basis, the present revision analyzed the role of sleep and its alterationin the promotion of obesity. Diverse studies indicate that subjects thatsleep less have greater possibility of becoming obese, and the shorteningof sleep increases the leptin/grelin reason, generating increase of theappetite and hunger. This can be associated to the biggest caloric intakeand promotion of obesity. An adequate standard of sleep becomes basicfor the regulation of body mass and must be stimulated by health profes-sionals. (Arq Bras Endocrinol Metab 2007;51/7:1041-1049)Keywords: Obesity; Sleep; Leptin; Ghrelin; Food intake O SISTEMA FISIOLOGICO QUE REGULA a massa corporal envolve tantocomponentes centrais como perifericos, os quais interagem com osaspectos ambientais, como a disponibilidade e a composicao da dieta e oexercicio fisico, influenciando, assim, a massa corporal. Embora a geneticadesempenhe um papel importante na determinacao da massa corporal, aaumentada prevalencia da obesidade nas ultimas decadas tem sido forte-mente relacionada com as mudancas no ambiente em que se vive. Ana-lisando as variaveis ambientais que sao provavelmente responsaveis pela“epidemia de obesidade”, a maior parte da atencao esta voltada para o es-tado, custo e composicao do alimento ingerido, e para a capacidade deanular o esforco fisico. No entanto, e possivel que outras variaveis am-

METABOLIC RESPONSES ON THE EARLY SHIFT

Shiftwork has been associated with a higher propensity for the development of metabolic disorders and obesity. The aim of the study was to investigate concentrations of glucose, cortisol, and insulin among fixed night workers (n = 9), fixed early morning workers (n = 6), and day workers (n = 7). Food intake was recorded for 7 days using a diary. Blood samples were collected every 4 h over the course of 24 h, yielding six samples. Total carbohydrate intake was lowest (p < .0005), whereas fat (p = .03) and protein (p < .0005) were highest on the early morning shifts. Early morning workers also had overall elevated cortisol levels relative to the other two groups. Cortisol levels appeared to be more influenced by time since waking prior to the shift than by time-of-day. Cortisol was highest for the early morning group than the day group 12 h after waking, and both the early morning and night groups had higher levels than the day group 16 h after waking (p < .05 in all cases). In contrast, the homesostatsis model assessment of insulin resistance (HOMA-IR) appeared to be more influenced by time-of-day than by time since waking prior to the shift. The early morning group had higher levels of HOMA-IR at 08:00 h than the other groups (p < .05). In conclusion, the early morning group had the highest overall concentrations of cortisol and tended to have higher levels of HOMA-IR, indicating that more attention should be given to these workers. Moreover, all three groups showed pronounced cortisol levels on awakening, suggesting that they may have adjusted to their awaking time. (Author: heloguarita@rgnutri.com.br)

A link between sleep loss, glucose metabolism and adipokines

The present review evaluates the role of sleep and its alteration in triggering problems of glucose metabolism and the possible involvement of adipokines in this process. A reduction in the amount of time spent sleeping has become an endemic condition in modern society, and a search of the current literature has found important associations between sleep loss and alterations of nutritional and metabolic contexts. Studies suggest that sleep loss is associated with problems in glucose metabolism and a higher risk for the development of insulin resistance and type 2 diabetes mellitus. The mechanism involved may be associated with the decreased efficacy of regulation of the hypothalamus-pituitary-adrenal axis by negative feedback mechanisms in sleep-deprivation conditions. In addition, changes in the circadian pattern of growth hormone (GH) secretion might also contribute to the alterations in glucose regulation observed during sleep loss. On the other hand, sleep deprivation stress affects adipokines - increasing tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and decreasing leptin and adiponectin -, thus establishing a possible association between sleep-debt, adipokines and glucose metabolism. Thus, a modified release of adipokines resulting from sleep deprivation could lead to a chronic sub-inflammatory state that could play a central role in the development of insulin resistance and type 2 diabetes mellitus. Further studies are necessary to investigate the role of sleep loss in adipokine release and its relationship with glucose metabolism.

Aplicação da escala de conhecimento nutricional em atletas profissionais e amadores de atletismo

An adequate nutrition is necessary to supply the energy demand required by exercise as much for active individuals and for athletes. However, much more than sports performance, the nutrition knowledge is essential for both populations for prevention of illnesses. Many interventions centered in nutritional education have been lead with the intention to increase nutrition knowledge and, consequently, improve nutritional behaviors. The aim of the present study was to evaluate the nutrition knowledge of professional and amateur track and field athletes with application of a scale previously validated in Brazil. The sample was composed by 26 professional and 41 amateur track and field athletes of several modalities in phase of continuous training. The results have shown that professional and amateur track and field athletes generally presented moderate nutritional knowledge, with the latter presenting punctuation significantly higher than the professional group, a fact associated with their higher educational background. In conclusion, professional track and field athletes present lower nutritional knowledge, which can be partly attributed to the fact that they see the nutritional science with performance as main objective. Further applications of this scale in professional and amateur athletes must be carried out in order to assess the nutritional knowledge level of this population.An adequate nutrition is necessary to supply the energy demand required by exercise as much for active individuals and for athletes. However, much more than sports performance, the nutrition knowledge is essential for both populations for prevention of illnesses. Many interventions centered in nutritional education have been lead with the intention to increase nutrition knowledge and, consequently, improve nutritional behaviors. The aim of the present study was to evaluate the nutrition knowledge of professional and amateur track and field athletes with application of a scale previously validated in Brazil. The sample was composed by 26 professional and 41 amateur track and field athletes of several modalities in phase of continuous training. The results have shown that professional and amateur track and field athletes generally presented moderate nutritional knowledge, with the latter presenting punctuation significantly higher than the professional group, a fact associated with their higher educational background. In conclusion, professional track and field athletes present lower nutritional knowledge, which can be partly attributed to the fact that they see the nutritional science with performance as main objective. Further applications of this scale in professional and amateur athletes must be carried out in order to assess the nutritional knowledge level of this population.

Adipokine levels are altered by shiftwork: a preliminary study.

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n = 9), working from 22:00 to 06:00 h; (ii) early morning shift (n = 6), working from 06:00 to 14:00 h; and (iii) day shift (n = 7), working from 08:00 to 17:00 h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24 h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p < .03). Both shiftworker groups ingested a significantly higher percentage of fat (p < .003) and a lower percentage of carbohydrate (p < .0005) than the day group. The early morning group had a lower mean 24-h level of adiponectin than the other two groups (p = .016), and both the early morning and night groups exhibited higher mean 24-h levels of TNF-α than the day group (p = .0001). The 24-h mean levels of IL-6 did not differ significantly between the groups (p = .147). None of the groups exhibited a significant circadian effect on adiponectin (p = .829), TNF-α (p = .779), or IL-6 (p = .979) levels. These results indicate that individuals who are enrolled in shiftwork are susceptible to alterations in the secretion of cytokines that are involved in insulin resistance and cardiovascular disease, both of which are known to affect this population. (Author correspondence: tmello@demello.net.br)