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

The Role of Anxiety and Depression in the Relationship Among Emotional Eating, Sleep Quality, and Impulsivity

ABSTRACT

The aim of this study was to investigate the relationship among sleep quality, impulsivity, anxiety, and depression in individuals with emotional eating behavior. The study was designed as a cross-sectional study. The study included 92 individuals (age 31.29 ± 9.17; female, 67.4% [ n = 62]; male, 32.6% [ n = 30]) with symptoms of emotional eating but no previous psychiatric diagnosis or treatment. Participants were administered a Structured Clinical Interview for DSM-5 Disorders interview form, a sociodemographic data form, the Emotional Eating Scale, the Beck Depression Scale, the Barratt Impulsivity Scale, the Beck Anxiety Scale, and the Pittsburgh Sleep Quality Index Scale. Emotional eating is positively correlated with anxiety ( r = 0.377, p = 0.001), depression ( r = 0.375, p = 0.001), impulsivity ( r = 0.250, p = 0.016), and poor sleep quality ( r = 0.478, p = 0.001). Obese individuals (defined as having a body mass index of 30 or higher) showed higher emotional eating ( z = -2.552, p = 0.016) and poorer sleep quality ( z = -2.089, p = 0.044) than nonobese individuals, and women showed higher emotional eating ( t = 2116, p = 0.037) and poorer sleep quality ( z = -2537, p = 0.010) than men. Poor sleep quality was associated with emotional eating. In this relationship, poor sleep quality influenced emotional eating through all mediators, including anxiety and depression ( B = 3.491; standardized effect, 0.485; p = 0.001). Poor sleep quality directly influenced emotional eating ( B = 2.806; standardized effect, 0.390; p = 0.001). The findings of the study suggest that emotional eating is associated with higher levels of anxiety, depression, impulsivity, and sleep problems, especially in women. It suggests that the interrelationships of psychological factors associated with emotional eating should be investigated.

Sleep deprivation in development of obesity, effects on appetite regulation, energy metabolism, and dietary choices

Sleep deprivation, which is a decrease in duration and quality of sleep, is a common problem in today's life. Epidemiological and interventional investigations have suggested a link between sleep deprivation and overweight/obesity. Sleep deprivation affects homeostatic and non-homoeostatic regulation of appetite, with the food reward system playing a dominant role. Factors such as sex and weight status affect this regulation; men and individuals with excess weight seem to be more sensitive to reward-driven and hedonistic regulation of food intake. Sleep deprivation may also affect weight through affecting physical activity and energy expenditure. In addition, sleep deprivation influences food selection and eating behaviours, which are mainly managed by the food reward system. Sleep-deprived individuals mostly crave for palatable energy-dense foods and have low desire for fruit and vegetables. Consumption of meals may not change but energy intake from snacks increases. The individuals have more desire for snacks with high sugar and saturated fat content. The relationship between sleep and the diet is mutual, implying that diet and eating behaviours also affect sleep duration and quality. Consuming healthy diets containing fruit and vegetables and food sources of protein and unsaturated fats and low quantities of saturated fat and sugar may be used as a diet strategy to improve sleep. Since the effects of sleep deficiency differ between animals and humans, only evidence from human subject studies has been included, controversies are discussed and the need for future investigations is highlighted.

Applying psycho-behavioural phenotyping in obesity characterization

Individual differences in obesity, beyond being explained by metabolic and medical complications, are understood by alterations in eating behaviour which underlie psychological processes. From this psychological perspective, studies have identified several potential characteristic features at the psycho-behavioural level that could additionally explain the maintenance of chronic excess weight or the unsuccessful results of current treatments. To date, despite the growing evidence, the heterogeneity of the psychological evidence associated with obesity has made it challenging to generate consensus on whether these psycho-behavioural phenotypes can be a complement to improve outcomes of existing interventions. For this reason, this narrative review is an overview focused on summarizing studies describing the psycho-behavioural phenotypes associated with obesity. Based on the literature, three psychological constructs have emerged: reward dependence, cognitive control, and mood and emotion. We discuss the clinical implications of stratifying and identifying these psycho-behavioural profiles as potential target for interventions which may ensure a better response to treatment in individuals with obesity. Our conclusions pointed out a considerable overlap between these psycho-behavioural phenotypes suggesting bidirectional interactions between them. These findings endorse the complexity of the psycho-behavioural features associated with obesity and reinforce the need to consider them in order to improve treatment outcomes.

Role of gender in explaining metabolic syndrome risk factors in an Iranian rural population using structural equation modelling

Many factors can lead to an increase in the prevalence of metabolic syndrome (MetS) in different populations. Using an advanced structural equation model (SEM), this study is aimed to determine the most important risk factors of MetS, as a continuous latent variable, using a large number of males and females. We also aimed to evaluate the interrelations among the associated factors involved in the development of MetS. This study used data derived from the Fasa PERSIAN cohort study, a branch of the PERSIAN cohort study, for participants aged 35 to 70 years with 10,138 males and females. SEM was used to evaluate the direct and indirect effects, as well as gender effects of influencing factors. Results from the SEM showed that in females most changes in MetS are described by waist circumference (WC), followed by hypertension (HP) and triglyceride (TG), while in males most changes in MetS are described by WC, followed by TG then fasting blood glucose (FBG). Results from the SEM confirmed the gender effects of social status on MetS, mediated by sleep and controlled by age, BMI, ethnicity and physical activity. This study also shows that the integration of TG and WC within genders could be useful as a screening criterion for MetS in our study population.

Impact of the first COVID-19 lockdown on body weight: A combined systematic review and a meta-analysis

The coronavirus disease 2019 (COVID-19) and the imposed lockdowns in order to control the pandemic, had undoubtedly influenced the lifestyle of millions of people worldwide. The period of confinement, which was characterized by seizing most business activities and allowing only for e-classes at schools and universities, leading also to a lower physical activity, could have affected eating behaviors of people of all ages. In this study we aimed to investigate the impact of the first lockdown period (March-May 2020) on body weight (BW) and on body mass index (BMI) in both adults and adolescents (>16 years old). A systematic literature search was conducted in PubMed®, Scopus®, Web of Science® and EMBASE® databases and 36 observational (35 cross-sectional and one cohort) studies were included. BW and BMI changes after/during the lockdown period were examined. BW was stated as increased in a significant part of the individuals (11.1-72.4%), although a range of 7.2-51.4% of individuals reported weight loss. A significant higher BW was observed with a weighted mean between-group difference (WMD) 1.57 (95% CI 1.01 to 2.14) in the post-lockdown period compared to the before lockdown time and higher BMI, 0.31 WMD (95% CI, 0.17 to 0.45) was identified before the lockdown period. At variance with general trends, one study in older adults (>60 years old) notably reported a significant BW loss, suggesting a higher risk for lockdown-induced weight loss and potentially malnutrition in the elderly population. Overall increments in BW are an alarming effect of lockdown during the COVID-19 pandemic, leading to potential higher incidence of overweight, obesity and related health-risks as well as other noncommunicable diseases. Further studies are needed to assess potential group-specific impacts, with particular regard to weight gain in younger people and risk of weight loss, malnutrition and sarcopenia in older adults.

The impact of COVID-19 lockdown on snacking habits, fast-food and alcohol consumption: A systematic review of the evidence

The pandemic of coronavirus disease 2019 (COVID-19) and lockdown measures, that were implemented in many countries in order to control the virus transmission, had negatively influenced the lifestyle of millions of people worldwide. In this study we aimed to investigate the impact of the first COVID-19 lockdown period (March-May 2020) on snacking behavior, fast-food and alcohol consumption. A systematic search in PubMed®, Scopus® and Web of Science® databases was conducted and 32 studies were included. Changes in snacking, in fast-food and ordered food consumption and in alcohol intake were examined. Snacking was found to be increased for a significant portion of the population examined (18.9-45.1%), whereas fast food (15.0-41.3%) and ordered food (33.9%) showed a tendency towards decrease. As per alcohol consumption, an upward trend was observed in a significant part (10.4-51.0%) of the participants examined. The increased snacking and alcohol consumption observed for almost a third of the examined population could be alarming because long-term health problems could arise in cases of repeated lockdowns in the future. The observed downward trend in fast-food consumption and in frequency of ordered food could be an encouraging sign of turning to home-prepared foods, but further research is needed in this field.

The relationships of shift work, hair cortisol concentration and dyslipidaemia: a cohort study in China

BACKGROUND

Currently, cardiovascular disease is the leading cause of death, and dyslipidaemia is an independent and modifiable major risk factor. Previous studies on shift work with dyslipidaemia and hair cortisol concentration (HCC) have yielded conflicting results. The aim of this study was to clarify the association between shift work, dyslipidaemia, and HCC. We further explored the mediating effect of HCC.

METHODS

In this cohort study, baseline data were collected from participants in May 2013. The cohort included 2170 participants- 1348 shift workers and 822 non-shift workers- who were followed up for 6 years with four questionnaire surveys from July 2014, October 2015, and May to December 2019. Hair samples were collected from 340 participants during the baseline period for HCC testing with an automated radioimmunoassay. Dyslipidaemia was defined using the National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria.

RESULTS

Shift workers had a higher risk of dyslipidaemia than workers on the fixed day shift (two-shift RR = 1.408, 95% CI: 1.102-1.798; three-shift RR = 1.478, 95% CI: 1.134-1.926; four-shift RR = 1.589, 95% CI: 1.253-2.015). Additionally, shift workers had higher HCC levels than fixed day shift workers, with geometric mean concentration (GMC) ± geometric standard difference (GSD) = 2.625 ± 2.012 ng/g, two-shift GMC ± GSD = 3.487 ± 1.930 ng/g, three-shift GMC ± GSD = 2.994 ± 1.813 ng/g, and four-shift GMC ± GSD = 3.143 ± 1.720 ng/g. High HCC was associated with a high incidence of dyslipidaemia. After controlling for confounding factors, this study showed that HCC played a role in mediating dyslipidaemia in shift workers and accounted for 16.24% of the effect.

CONCLUSIONS

Shift work was linked to increased risk of dyslipidaemia compared with fixed day shift work. Higher HCC was associated with a higher prevalence of dyslipidaemia. HCC had a significant mediating effect on dyslipidaemia in shift workers.

The association between modified Nordic diet with sleep quality and circadian rhythm in overweight and obese woman: a cross-sectional study

OBJECTIVE

Previous studies have shown an association between diet quality and sleep quality. The objective of this study was to investigate the association between modified Nordic diet with sleep quality and circadian rhythm in overweight and obese woman.

METHODS

We enrolled 399 overweight and obese women (body mass index (BMI): 25-40 kg/m²), aged 18-48 years, in this cross-sectional study. For each participant, anthropometric measurements, biochemical tests, and food intake were evaluated. Sleep quality and circadian rhythm was measured by Pittsburgh Sleep Quality Index (PSQI) and morning-evening questionnaire (MEQ) questionnaire. Modified Nordic diet score was measured using a validated 147-item food frequency questionnaire (FFQ).

RESULTS

Overall, 51.7% of the subjects were good sleepers (the Pittsburgh Sleep Quality Index (PSQI) < 5) while 48.3% were poor sleepers (PSQI ≥ 5). Moreover, participants were divided into five groups of MEQ, namely, completely morning 8 (2.4%), rarely morning 82 (24.8%), normal 196 (59.2%), rarely evening 43 (13%), and completely evening 2 (0.6%). After controlling for confounders, there was a significant association between poor sleep quality and the modified Nordic diet (OR = 0.80, %95 CI = 0.66-0.98, P = 0.01). Moreover, a significant positive association was observed between the completely morning and modified Nordic diet (OR = 1.80, %95 CI = 0.54-6.00, P = 0.03), in addition to a significant inverse association between the completely evening type and modified Nordic diet (OR = 0.16, %95 CI = 0.002-5.41, P = 0.02).

CONCLUSIONS

The present study indicated that higher adherence to a modified Nordic diet reduces poor sleep quality. Also, the completely morning type was associated with higher adherence to a modified Nordic diet, and completely evening type was associated with lower adherence to a modified Nordic diet.

LEVELS OF EVIDENCE

Level IV, evidence obtained from multiple time series analysis.

A Time to Rest, a Time to Dine: Sleep, Time-Restricted Eating, and Cardiometabolic Health

Cardiovascular disease (CVD) poses a serious health and economic burden worldwide. Modifiable lifestyle factors are a focus of research into reducing the burden of CVD, with diet as one of the most investigated factors. Specifically, the timing and regularity of food intake is an emerging research area, with approaches such as time-restricted eating (TRE) receiving much attention. TRE involves shortening the time available to eat across the day and is associated with improved CVD outcomes compared with longer eating windows. However, studies that have examined TRE have not considered the impact of sleep on CVD outcomes despite recent evidence showing that sleep duration can influence the timing and amount of food eaten. In this article, we argue that as TRE and sleep influence each other, and influence the same cardiometabolic parameters, experiencing inadequate sleep may attenuate any positive impact TRE has on CVD. We examine the relationship between TRE and CVD, with sleep as a potential mediator in this relationship, and propose a research agenda to investigate this relationship. This will provide necessary evidence to inform future interventions aimed at reducing the burden of CVD.

REM Sleep Deprivation Impairs Learning and Memory by Decreasing Brain O-GlcNAc Cycling in Mouse

Rapid eye movement (REM) sleep is implicated learning and memory (L/M) functions and hippocampal long-term potentiation (LTP). Here, we demonstrate that REM sleep deprivation (REMSD)-induced impairment of contextual fear memory in mouse is linked to a reduction in hexosamine biosynthetic pathway (HBP)/O-GlcNAc flux in mouse brain. In mice exposed to REMSD, O-GlcNAcylation, and O-GlcNAc transferase (OGT) were downregulated while O-GlcNAcase was upregulated compared to control mouse brain. Foot shock fear conditioning (FC) induced activation of protein kinase A (PKA) and cAMP response element binding protein (CREB), which were significantly inhibited in brains of the REMSD group. Intriguingly, REMSD-induced defects in L/M functions and FC-induced PKA/CREB activation were restored upon increasing O-GlcNAc cycling with glucosamine (GlcN) or Thiamet G. Furthermore, Thiamet G restored the REMSD-induced decrease in dendritic spine density. Suppression of O-GlcNAcylation by the glutamine fructose-6-phosphate amidotransferase (GFAT) inhibitor, 6-diazo-5-oxo-L-norleucine (DON), or OGT inhibitor, OSMI-1, impaired memory function, and inhibited FC-induced PKA/CREB activation. DON additionally reduced the amplitude of baseline field excitatory postsynaptic potential (fEPSP) and magnitude of long-term potentiation (LTP) in normal mouse hippocampal slices. To our knowledge, this is the first study to provide comprehensive evidence of dynamic O-GlcNAcylation changes during the L/M process in mice and defects in this pathway in the brain of REM sleep-deprived mice. Our collective results highlight HBP/O-GlcNAc cycling as a novel molecular link between sleep and cognitive function.

Assessment of eating habits and lifestyle during the coronavirus 2019 pandemic in the Middle East and North Africa region: a cross-sectional study

Coronavirus disease 2019 (COVID-19) has rapidly spread globally, forcing countries to apply lockdowns and strict social distancing measures. The aim of this study was to assess eating habits and lifestyle behaviours among residents of the Middle East and North Africa (MENA) region during the lockdown. A cross-sectional study among adult residents of the MENA region was conducted using an online questionnaire designed on Google Forms during April 2020. A total of 2970 participants from eighteen countries participated in the present study. During the pandemic, over 30 % reported weight gain, 6·2 % consumed five or more meals per d compared with 2·2 % before the pandemic (P < 0·001) and 48·8 % did not consume fruits on a daily basis. Moreover, 39·1 % did not engage in physical activity, and over 35 % spent more than 5 h/d on screens. A significant association between the frequency of training during the pandemic and the reported change in weight was found (P < 0·001). A significantly higher percentage of participants reported physical and emotional exhaustion, irritability and tension either all the time or a large part of the time during the pandemic (P < 0·001). Although a high percentage of participants reported sleeping more hours per night during the pandemic, 63 % had sleep disturbances. The study highlights that the lockdown due to the COVID-19 pandemic caused a variety of lifestyle changes, physical inactivity and psychological problems among adults in the MENA region.

Addiction-like response in brain and behavior in a rat experimental model of night-eating syndrome

STUDY OBJECTIVES

Individuals ailing from night eating syndrome (NES) consume more than 25% of their daily food intake during the normal sleep time, delaying their sleep or waking up in the middle of the night to eat. This study explored two experimental conditions resembling NES in Wistar rats by offering palatable food during the sleep phase, alone or combined with sleep delay. Also we explored their impact on addiction-like changes in the brain and behavior.

METHODS

Experiment 1 explored the brain response after a first NES-like event; experiment 2 and 3 explored addiction-like behaviors c-Fos and FosB/ΔFosB in corticolimbic regions after 4 weeks exposition to NES-like conditions and after one week of withdrawal, respectively. For all 3 experiments 6 experimental groups were used: 1. Control; 2. Restricted access (1 h) to high-sugar diet (HSD) or to 3. high-fat diet (HFD); 4., Sleep delay for 4 h (SD) (from ZT0-ZT4, rats using slow rotating wheels); 5. SD + HSD; 6. SD + HFD.

RESULTS

A first event of eating a palatable diet with or without SD was sufficient to stimulate c-Fos and ΔFosB. Along 4 weeks of exposure to the palatable diets rats exhibited escalation and binge eating, which was highest for the HFD. At this stage, SD did not influence behavioral changes nor the neuronal response. After one-week in withdrawal, rats exhibited craving and effort to obtain their palatable diet. The brains of rats previously exposed to sleep delay maintained high levels of FosB/ΔFosB in the accumbens shell and high c-Fos activation in the insular cortex.

CONCLUSIONS

In our experimental models of NES-like a HFD in the sleep phase and SD are risk factors to develop binge eating and addiction-like behaviors.

Eating Duration throughout a Rotating Shift Schedule: A Case Study

OBJECTIVE

The impact of the rotation between different shifts and free days within a short period of time on the food consumption is poorly addressed in the literature. Our objective was to characterize the eating duration (ED) over 10 d of clockwise rotating and to associate it with the intake of energy and macronutrients.

METHODS

Thirty male shift-workers from a mining company were evaluated over a complete rotation shift schedule of 10 consecutive days (2 d of morning shifts, 2 d of afternoon shifts, 24 h free-day, 2 d of night shifts, and three free days). ED was defined as the interval between the first meal after awaking and last meal before sleep onset. Sleep/wake periods and food intake were evaluated by actigraphy and 24 h recalls, respectively. Generalized models were used to analyze the variation in ED and its association with nutrient intake over the shift schedule.

RESULTS

ED periods showed significant variations throughout shift rotation and were associated with energy intake. The highest energy intake (3410 ± 235 kcal) and longest ED (20.7 ± 1.2 h) were found on Day 5, the day between afternoon and night shifts, and a part of Day 6 (night shift), i.e., in the longest period of wakefulness and the shortest sleep duration (4.7 ± 0.3 h) (p < 0.05 for all). The lowest energy intake (1284 ± 125 kcal) and shortest ED (4.96 ± 0.7 h) (p < 0.05) occurred after the last night shift (Day 7). The balance between the percentage of macronutrients did not differ statistically between the ED periods.

CONCLUSIONS

In general, longer periods of wakefulness showed greater energy intake, demonstrating the tendency of workers to eat around the clock during their shift. Even with the energy intake variation, the balance of macronutrients remained the same over the ED periods. Despite the need of confirmation in future studies, these results suggest that the management of ED period could be considered in the nutritional approach of shift workers.

Major dietary patterns in relation to obesity and quality of sleep among female university students

BACKGROUND

Few studies reported the association of dietary patterns with obesity, central adiposity, and quality of sleep. We aimed to investigate the association between major dietary patterns and anthropometric indices in relation to obesity and quality of sleep among female students of Ahvaz Jundishapur University of Medical Sciences (AJUMS).

METHODS

This cross-sectional study was conducted on 245 female university students aged 18-38 years. To assess sleep quality, we used a self-reported Pittsburgh sleep quality index (PSQI). Usual dietary intakes were assessed with the use of a 168 items food frequency questionnaire (FFQ). We used factor analysis to identify dietary patterns.

RESULTS

Four major dietary patterns were identified: mixed, high protein, Western, and healthy dietary patterns. After adjustment for energy intake, subjects in the upper tertile of the mixed dietary pattern were more likely to have a high quality of sleep than those in the first tertile (odds ratio [OR]: 0.27; 95% CI: 0.13, 0.55). Individuals with greater adherence to Western dietary pattern had greater odds of having low quality of sleep compared to those in the first tertile (OR: 1.99; 95% CI: 1.04, 3.82). A healthy dietary pattern was associated with a higher quality of sleep; however, the association was no longer significant after adjustment for dietary energy intake. No significant association was found for high protein dietary patterns. Compared to the first tertile of the healthy dietary pattern, individuals in the upper tertile were less likely to be centrally obese (OR = 0.15; 95% CI = 0.50-0.52). Participants in the last tertile of the high protein dietary pattern were less likely to be generally obese (OR = 0.34; 95% CI = 0.12-0.99), whereas those in the upper tertile of the Western dietary pattern were more likely to be generally obese (OR = 1.84; 95% CI = 1.08-4.93).

CONCLUSIONS

Adherence to a mixed dietary pattern was associated with a high quality of sleep; however, the result was not significant for a high protein dietary pattern. While the high protein dietary pattern was negatively associated with general and central obesity, students in the upper tertile of the Western dietary pattern were more likely to be generally obese.

A High-Protein Meal during a Night Shift Does Not Improve Postprandial Metabolic Response the Following Breakfast: A Randomized Crossover Study with Night Workers

The aim of this study was to compare the acute effect of a high-protein/moderate carbohydrate (HP-MCHO) versus low-protein/high-carbohydrate (LP-HCHO) meal served at night on the postprandial metabolic response of male night workers the following breakfast. A randomized crossover study was performed with 14 male night workers (40.9 ± 8.9 years old; 29.1 ± 5.3 kg/m²). Participants underwent two different isocaloric dietary conditions at 1:00 h of the night shift: HP-MCHO (45 en% carbohydrate, 35 en% protein and 20 en% fat) and LP-HCHO (65 en% carbohydrate, 15 en% protein and 20 en% fat). Postprandial capillary glucose levels were determined immediately before the intake of the test meal and 30, 60, 90 and 120 min after the end of the meal. At the end of the work shift (6:30 h), participants received a standard breakfast and postprandial levels of glucose, insulin and triglycerides were determined immediately before and then every 30 min for 2 h (30, 60, 90 and 120 min). Higher values of capillary glucose were found after the LP-HCHO condition compared to the HP-MCHO condition (area under the curve (AUC) = 119.46 ± 1.49 mg/dL × min and 102.95 ± 1.28 mg/dL × min, respectively; p < 0.001). For the metabolic response to standard breakfast as the following meal, no significant differences in glucose, insulin, triglyceride, and HOMA-IR levels were found between interventions. A night meal with a higher percentage of protein and a lower percentage of carbohydrate led to minor postprandial glucose levels during the night shift but exerted no effect on the metabolic response of the following meal. This trial was registered at ClinicalTrials.gov as NCT03456219.

Shift rotation, circadian misalignment and excessive body weight influence psychomotor performance: a prospective and observational study under real life conditions

We aimed to evaluate the influence of shift work rotation, circadian misalignment and being overweight/obese on psychomotor performance throughout a complete shift rotation schedule. The study was conducted with 30 males working rotating shifts from a mining company under real life conditions. Individuals were evaluated over seven days in a shift schedule carried out as follow: two shifts in the morning (D1 and D2), two shifts in the afternoon (D3 and D4), 24 hour free day (D5) and two shifts at night (D6 and D7). Work performance was evaluated by psychomotor vigilance task tests (PVT), and actigraphy was used to characterise the rest-activity rhythm based on intradaily variability (IV) and interdaily stability (IS) of nonparametric functions. We found a significant effect of the shift, body mass index (BMI), IS and IV on lapses in attention. More lapses occurred on D7 than D1, D2, D3 and D4 of the schedule shift. The obese group presented a higher number of lapses in attention than eutrophic. The interaction between day and IS showed that less synchronised individuals presented a higher number of lapses in attention on D7 than D1 and, for the interaction between day and IV, more fragmented individuals presented a higher number of lapses in attention on D7 than D6. We conclude that higher BMI, lower synchronisation and higher fragmentation of the rest-activity pattern influenced lapses in attention throughout the shift rotation.

Prudent diet is associated with low sleepiness among short-haul truck drivers

OBJECTIVES

The lifestyle of postindustrial society has undergone major shifts characterized by changes in demographic and epidemiologic profiles, eating habits, and job structures, with irregular working hours, particularly night shifts. The investigation of dietary patterns is of great importance for the discussion and devising of effective dietary strategies for shift and night workers in general, particularly in view of the increased sleepiness reported during night work.

OBJECTIVE

We aimed to determine the association between dietary patterns of Brazilian truck drivers and sleepiness levels, according to work shift.

METHODS

A cross-sectional study of 52 drivers (25 long haul and 27 short haul) at a freight company was carried out. This study entailed application of a structured questionnaire collecting sociodemographic, lifestyle, and nutritional status data. Assessment of dietary intake using a 24-h dietary recall and an evaluation of sleepiness by the Karolinska Sleepiness Scale were performed. The principal components of the diet were analyzed by factor analysis to derive dietary patterns. A linear mixed model was then applied to determine a model for sleepiness levels of the drivers as a function of dietary pattern, time of day, and work shift.

RESULTS

Three intake patterns were derived: traditional, prudent, and Western. Associations of time of day (F = 23.629, P < 0.01) and shift type (F = 42.218, P < 0.01) on sleepiness were found. An association between diet and sleepiness was also evident, where the prudent pattern was associated with low sleepiness among short-haul truck drivers (F = 3.865, P = 0.02).

CONCLUSIONS

The results of the present study revealed an association between dietary patterns and short-haul driving, in which the healthy pattern produced low sleepiness during the day. The sleepiness curve of long-haul drivers appears to have a flattening pattern, probably because of irregular working times.

Social jet-lag potentiates obesity and metabolic syndrome when combined with cafeteria diet in rats

BACKGROUND/OBJECTIVES

Modern lifestyle promotes shifted sleep onset and shifted wake up time between weekdays and weekends, producing a condition termed "social-jet lag." Disrupted sleep promotes increased appetite for carbohydrate and fat-rich food, which in long term leads to overweight, obesity and metabolic syndrome. In order to mimic the human situation we produced an experimental model of social-jet lag (Sj-l). With this model, we explored the link between shifted sleep time with consumption of a cafeteria diet (CafD) and the development of obesity and metabolic syndrome.

SUBJECTS/METHODS

The first experiment was designed to create and confirm the model of Sj-l. Rats (n=8-10/group) were exposed to a shifted sleep time protocol achieved by placing the rats in slow rotating wheels from Monday to Friday during the first 4h of the light period, while on weekends they were left undisturbed. The second experiment (n=8-12/group) explored the combined effect of Sj-l with the opportunity to ingest CafD. All protocols lasted 12weeks. We evaluated the development of overweight and indicators of metabolic syndrome. The statistical significance for all variables was set at P<0.05.

RESULTS

Sj-l alone did not affect body weight gain but induced significant changes in cholesterol in metabolic variables representing a risk factor for metabolic syndrome. Daily restricted access to CafD in the day or night induced glucose intolerance and only CafD during the day led to overweight. Sj-l combined with CafD induced overconsumption of the diet, potentiated body weight gain (16%) and promoted 5 of the criteria for metabolic syndrome including high insulin and dislipidemia.

CONCLUSION

Present data provide an experimental model of social-jet lag that combined with overconsumption of CafD, and maximized the development of obesity and metabolic syndrome. Importantly, access to CafD during the night did not lead to overweight nor metabolic syndrome.

Behavioral Factors Related to Sleep Quality and Duration in Adults

BACKGROUND

The purpose of this study was to measure the sleep quality and duration in healthy adults and to identify any influencing factors.

METHODS

This study was a descriptive research investigation that evaluated 240 healthy adults at least 19 years of age. The data were assessed using the following self-administered questionnaires: the Pittsburgh Sleep Quality Index (PSQI), the Beck Depression Inventory, the State-Trait Anxiety Inventory-Korean YZ, and the Fatigue Severity Scale.

RESULTS

The PSQI global score was 5.69 ± 3.23, and 59.6% of the participants were classified as having poor quality sleep (PSQI score > 5). The significant risk factors for poor sleep quality were female gender (p = 0.021), number of comorbid conditions (p = 0.003), depression (p < 0.001), fatigue (p < 0.001), and anxiety (p < 0.001). Stepwise multiple regression analyses showed that significant predictors of poor sleep quality were depression (p < 0.001) and fatigue (p < 0.001). Participants slept an average of 6.16 ± 1.36 hours a night. A shorter sleep duration was correlated with older age (p = 0.010), a higher body mass index (BMI) (p = 0.026), a greater depression score (p = 0.002), a higher fatigue score (p = 0.028), and lower sleep quality (p < 0.001). In addition, stepwise multiple regression analyses revealed that factors significantly associated with sleep duration were depression (p = 0.002) and BMI (p = 0.034).

CONCLUSION

The number of comorbid conditions and the presence of depression and fatigue were risk factors for both low sleep quality and short sleep duration. Therefore, to improve sleep quality, there is a need for comprehensive interventional programs to manage these and any other factors that disturb sleep.

Short-term feeding at the wrong time is sufficient to desynchronize peripheral clocks and induce obesity with hyperphagia, physical inactivity and metabolic disorders in mice

BACKGROUND

The circadian clock regulates various physiological and behavioral rhythms such as feeding and locomotor activity. Feeding at unusual times of the day (inactive phase) is thought to be associated with obesity and metabolic disorders in experimental animals and in humans.

OBJECTIVE

The present study aimed to determine the underlying mechanisms through which time-of-day-dependent feeding influences metabolic homeostasis.

METHODS

We compared food consumption, wheel-running activity, core body temperature, hormonal and metabolic variables in blood, lipid accumulation in the liver, circadian expression of clock and metabolic genes in peripheral tissues, and body weight gain between mice fed only during the sleep phase (DF, daytime feeding) and those fed only during the active phase (NF, nighttime feeding). All mice were fed with the same high-fat high-sucrose diet throughout the experiment. To the best of our knowledge, this is the first study to examine the metabolic effects of time-imposed restricted feeding (RF) in mice with free access to a running wheel.

RESULTS

After one week of RF, DF mice gained more weight and developed hyperphagia, higher feed efficiency and more adiposity than NF mice. The daily amount of running on the wheel was rapidly and obviously reduced by DF, which might have been the result of time-of-day-dependent hypothermia. The amount of daily food consumption and hypothalamic mRNA expression of orexigenic neuropeptide Y and agouti-related protein were significantly higher in DF, than in NF mice, although levels of plasma leptin that fluctuate in an RF-dependent circadian manner, were significantly higher in DF mice. These findings suggested that the DF induced leptin resistance. The circadian phases of plasma insulin and ghrelin were synchronized to RF, although the corticosterone phase was unaffected. Peak levels of plasma insulin were remarkably higher in DF mice, although HOMA-IR was identical between the two groups. Significantly more free fatty acids, triglycerides and cholesterol accumulated in the livers of DF, than NF mice, which resulted from the increased expression of lipogenic genes such as Scd1, Acaca, and Fasn. Temporal expression of circadian clock genes became synchronized to RF in the liver but not in skeletal muscle, suggesting that uncoupling metabolic rhythms between the liver and skeletal muscle also contribute to DF-induced adiposity.

CONCLUSION

Feeding at an unusual time of day (inactive phase) desynchronizes peripheral clocks and causes obesity and metabolic disorders by inducing leptin resistance, hyperphagia, physical inactivity, hepatic fat accumulation and adiposity.

Intake of stimulant foods is associated with development of parasomnias in children

OBJECTIVE

To verify if nighttime feeding habits can influence parasomnia in children.

METHOD

Seven private and four public Elementary Schools took part in the study. A total of 595 Sleep Disturbance Scale for Children were distributed to the parents of children aged from 7 to 8 years. Data of dietary recall, starting time to school, physical activity, and nutritional status were studied.

RESULTS

Of the 226 questionnaires completed, 92 (41%) reported parasomnia. Girls had 2.3 times more the chance to parasomnia than boys. Children who consumed stimulant foods had 2.6 times more chance to have parasomnia than those of children who consumed non-stimulant foods. There were no difference between parasomnia and no-parasomnia groups in food type (p = 0.78) or timing of last meal before bedtime (p = 0.50).

CONCLUSION

Our findings suggest that intake of stimulant foods is associated with development of parasomnia in children.

Interactions between sleep, stress, and metabolism: From physiological to pathological conditions

Poor sleep quality due to sleep disorders and sleep loss is highly prevalent in the modern society. Underlying mechanisms show that stress is involved in the relationship between sleep and metabolism through hypothalamic–pituitary–adrenal (HPA) axis activation. Sleep deprivation and sleep disorders are associated with maladaptive changes in the HPA axis, leading to neuroendocrine dysregulation. Excess of glucocorticoids increase glucose and insulin and decrease adiponectin levels. Thus, this review provides overall view of the relationship between sleep, stress, and metabolism from basic physiology to pathological conditions, highlighting effective treatments for metabolic disturbances.

[Nutritional damages and disturbances in the sleep pattern of nursing workers]

This article presents an integrative review of national and international scientific publications that investigate the sleep habits, the feed intake and nutritional status of nursing professionals. It was analyzed articles published in national and international journals in the period 2002 to 2014 and made available in the database PubMed / MEDLINE (USA National Library of Medicine), Lilacs / SciELO (Scientific Eletronic Library Online) and Google Scholar. Thirty one articles met the criteria. In the analysis of these studies it has been found a high prevalence of overweight and obesity, a negative change in the eating habits, as well as losses in the sleep patterns of nursing professionals.

Maquinistas ferroviários: trabalho em turnos e repercussões na saúde

Objetivo descrever o impacto do trabalho em turnos na saúde, no sono e na qualidade de vida de maquinistas ferroviários. Métodos foram avaliados 611 maquinistas (escalas de trabalho 4 x 1 e 6 x 2), por meio de polissonografia, Índice da Qualidade do Sono de Pittsburgh, Índice de Gravidade de Insônia, Questionário de Qualidade de Vida SF-36, Questionário de Horne e Östberg, Capacidade de Trabalho e Escala de Sonolência de Epworth. Resultados os maquinistas apresentaram idade média de 36,6 ± 15,1 anos, 22% apresentaram obesidade e 38,1% risco para doenças cardiovasculares. Em relação ao sono, 64,2% dos maquinistas relataram qualidade ruim de sono, 11,6% apresentaram distúrbios do sono e 29,3% sonolência excessiva. Os resultados da polissonografia mostraram que 36,1% deles apresentaram apneia do sono e 47,2% demonstraram eficiência do sono reduzida. Além disso, os maquinistas apresentaram baixos índices de qualidade de vida, especialmente os da escala 4 x 1. Conclusão é possível afirmar, na população estudada, que a exposição ao trabalho em turnos, a rotatividade inversa, pouco tempo dispensado às folgas e horas extras de trabalho estão associados a danos ao bem-estar, saúde, sociabilização e ao sono de qualidade desses trabalhadores e que provavelmente os fatores relacionados aos turnos de trabalho contribuem para esses danos.

Obesity and sleepiness in women with fibromyalgia

Fibromyalgia (FM) is associated with a number of comorbidities, including chronic widespread pain, fatigue and non-restorative sleep. Evidence has shown that FM is closely associated with overweight and obesity. The objective of the present study was to investigate the relationship between obesity and sleepiness in women with FM. A total of 100 adult female patients with a prior medical diagnosis of FM participated in the study. Body mass, height and waist circumference were measured, and body mass index (BMI) was calculated. The diet quality was evaluated by the Healthy Eating Index. Subjective analyses of daytime sleepiness [Epworth Sleepiness Scale (ESS)] and sleep quality (Pittsburgh Sleep Quality) were performed. An obesity rate of 41 % was found in all women (56.1 % were sleepy and 43.9 % were not, p = 0.04). Obese women showed a greater level of sleepiness when compared with non-obese (10.2 and 7.0, respectively, p = 0.004). Sleepy women showed a greater weight gain after the diagnosis of FM when compared with non-sleepy women (11.7 and 6.4 kg, respectively, p = 0.04). A positive and significant correlation between BMI and sleepiness (r = 0.35, p = 0.02) was also found. In multivariate logistic regression, moderate or severe sleepiness (ESS >12) was associated with obesity (odds ratio 3.44, 95 % CI 1.31-9.01, p = 0.04). These results demonstrate an important association between sleepiness and FM, suggesting that the occurrence of obesity may be involved with sleepiness in these patients.

Night eating behavior and metabolic heath in mothers and fathers enrolled in the QUALITY cohort study

BACKGROUND

Desynchrony between eating and sleeping patterns and poor sleep quality have been associated with obesity and metabolic abnormalities. This study examined the metabolic health correlates of night eating syndrome in adults enrolled in the QUALITY cohort study.

METHODS

Night eating symptoms were assessed in 310 women (mean age = 40.3 ± 5.1 years, mean BMI = 28.8 ± 6.2 kg/m(2)) and 305 men (mean age = 42.5 ± 5.9 years, mean BMI = 30.3 ± 5.0 kg/m(2)). Anthropometric measures, fasting blood samples and blood pressure were used to diagnose metabolic syndrome (MetS) and type 2 diabetes (T2D) diagnosis was self-report. Correlational and case/control comparisons assessed night eating symptoms in persons with and without MetS and T2D.

RESULTS

Night eating questionnaire (NEQ) scores were positively correlated with BMI. When controlling for BMI, NEQ scores were significantly negatively correlated with blood pressure in women and positively correlated with waist circumference and triglycerides in men. MetS diagnosis was associated with morning anorexia in both women and men and urges to eat at night in women only. T2D was associated with a depressed mood in women and with insomnia in men.

CONCLUSION

Symptoms of night eating syndrome are associated with higher BMI and poor metabolic health. Future research is needed to determine if night eating syndrome per se is a unique causal pathway in the development of obesity and metabolic disease.

Ghrelin and its interactions with growth hormone, leptin and orexins: implications for the sleep-wake cycle and metabolism

Several studies have shown that ghrelin administration promotes wakefulness in rodents, while in human males it induces sleep but has no effect in women. Ghrelin also plays an important role in metabolism and appetite regulation, and as described in this review may participate in the energy balance during sleep. In this review, we summarize some of the effects induced by ghrelin administration on the sleep-wake cycle in relation to the effects of other hormones, such as growth hormone, leptin, and orexin. Finally we discuss the relationship between sleep deprivation, obesity and ghrelin secretion pattern.

Disordered eating behaviors and sleep disturbances

The aim of the present study was to investigate if disordered eating behaviors predicted the development of sleep disturbances. A total of 870 students participated at baseline, 592 one year later (T1) and 305 two years later (T2). The Eating Attitudes Test-40 was used to assess global disordered eating behaviors, dietary concerns (DC), bulimic behaviors (BB) and social pressure to eat (SPE). Sleep disturbances were assessed by two items related to difficulties initiating sleep (DIS) and maintaining sleep (DMS). A sleep disturbance index (SDI) was calculated by summing DIS and DMS scores. Results revealed that global disordered eating behaviors at baseline predicted DIS, DMS and SDI at T1 and T2. Students with increased BB and SPE scores at baseline were more likely to experience sleep onset and sleep maintenance difficulties in the long term. These results suggest that assessment and correction of eating behaviors might prevent sleep disturbances.

Association between body mass index and sleep duration assessed by objective methods in a representative sample of the adult population

INTRODUCTION

Sleep duration has been associated with overweight individuals in many epidemiological studies; however, few studies have assessed sleep using objective methods. Our study was designed to evaluate the association between body mass index (BMI) and sleep duration measured by actigraphy (Acti), polysomnography (PSG) and the Pittsburgh sleep quality index questionnaire (PSQIO). Furthermore, we evaluated other biochemical and polysomnographic parameters.

METHODS

A representative sample of 1042 individuals from Sao Paulo, Brazil, including both genders (20-80 yrs), participated in our protocol. Weight and other anthropometric parameters were measured at the onset of the study. Sleep duration was calculated by Acti, PSG, and the PSQIQ. The population was sorted by sleep duration, body, slow wave sleep (SWS) and REM sleep (REMS) duration subsets. In addition, other biochemical and polysomnographic parameters were analyzed. Differences between population subsets were analyzed by one-way analysis of variance (ANOVA). Linear regression analysis was performed between sleep and anthropometric parameters.

RESULTS

Shorter sleep duration was associated with higher BMI and waist and neck circumference when measured by Acti and PSG (p<0.05). Lower leptin levels were associated with short sleep in normal-weight (BMI>18 and ⩽25) individuals (p<0.01). The association between short sleep duration Acti and higher BMI was present when apnea-hypopnea index (AHI) was less than 15 (p=0.049). Shorter REMS and SWS also were associated with higher BMI (p<0.01). Normal-weight individuals tended to sleep longer, have higher sleep efficiency and longer SWS and REMS than obese individuals (Acti, PSG; p=0.05). Sleep duration was negatively correlated with BMI (Acti, PSG; p<0.05). Short SWS and REMS were associated with higher cardiovascular risk factors (p<0.05).

CONCLUSION

Shorter sleep, SWS, and REMS duration were associated with higher BMI, central adiposity measurements, and cardiovascular risk factors when measured by objective methods.

Beyond pharmacotherapy: understanding the links between obesity and chronic mental illness

While differences in weight-gain potential exist, both between and within classes of psychiatry medications, most commonly used atypical antipsychotics, mood stabilizers, and antidepressants result in some degree of weight gain. This is not new information and it requires an understanding of the tolerability profiles of different treatments and their goodness of fit with specific patient phenotypes. However, this iatrogenic association represents only a piece of this obesity-mental illness dyad. The complex interplay between psychiatric illness and weight involves neurobiology, psychology, and sociological factors. Parsing the salient variables in people with mental illness is an urgent need insofar as mortality from physical health causes is the most common cause of premature mortality in people with chronic mental illness. Our review examines issues associated with common chronic mental illnesses that may underlie this association and warrant further study if we hope to clinically intervene to control this life-threatening comorbidity.

Sleep deprivation affects inflammatory marker expression in adipose tissue

Sleep deprivation has been shown to increase inflammatory markers in rat sera and peripheral blood mononuclear cells. Inflammation is a condition associated with pathologies such as obesity, cancer, and cardiovascular diseases. We investigated changes in the pro and anti-inflammatory cytokines and adipokines in different depots of white adipose tissue in rats. We also assessed lipid profiles and serum levels of corticosterone, leptin, and adiponectin after 96 hours of sleep deprivation.

Methods

The study consisted of two groups: a control (C) group and a paradoxical sleep deprivation by 96 h (PSD) group. Ten rats were randomly assigned to either the control group (C) or the PSD. Mesenteric (MEAT) and retroperitoneal (RPAT) adipose tissue, liver and serum were collected following completion of the PSD protocol. Levels of interleukin (IL)-6, interleukin (IL)-10 and tumour necrosis factor (TNF)-α were analysed in MEAT and RPAT, and leptin, adiponectin, glucose, corticosterone and lipid profile levels were analysed in serum.

Results

IL-6 levels were elevated in RPAT but remained unchanged in MEAT after PSD. IL-10 protein concentration was not altered in either depot, and TNF-α levels decreased in MEAT. Glucose, triglycerides (TG), VLDL and leptin decreased in serum after 96 hours of PSD; adiponectin was not altered and corticosterone was increased.

Conclusion

PSD decreased fat mass and may modulate the cytokine content in different depots of adipose tissue. The inflammatory response was diminished in both depots of adipose tissue, with increased IL-6 levels in RPAT and decreased TNF-α protein concentrations in MEAT and increased levels of corticosterone in serum.

Sleep and metabolism: role of hypothalamic neuronal circuitry

Sleep and metabolism are intertwined physiologically and behaviorally, but the neural systems underlying their coordination are still poorly understood. The hypothalamus is likely to play a major role in the regulation sleep, metabolism, and their interaction. And increasing evidence suggests that hypocretin cells in the lateral hypothalamus may provide particularly important contributions. Here we review: 1) direct interactions between biological arousal and metabolic systems in the hypothalamus, and 2) indirect interactions between these two systems mediated by stress or reward, emphasizing the role of hypocretins. An increased understanding of the mechanisms underlying these interactions may provide novel approaches for the treatment of patients with sleep disorders and obesity, as well as suggest new therapeutic strategies for symptoms of aging, stress, or addiction.

Sleep disturbances, body mass index and eating behaviour in undergraduate students

This study investigates the association between sleep disturbances, body mass index (BMI) and eating behaviour in a sample of undergraduate students. The sample comprises 870 medicine and dentistry students from Coimbra University (62.5% females), aged between 17 and 25 years. The Eating Attitudes Test-40 was used to measure eating behaviour, and two questions were applied addressing difficulties of initiating sleep (DIS) and difficulties of maintaining sleep (DMS). A sleep disturbance index (SDI) was calculated from the sum of DIS and DMS scores. Body mass index (BMI) was determined from self-reported weight and height. The correlation analyses generally indicated that global eating disturbance, bulimic behaviour dimension and social pressure to eat were associated particularly with sleep difficulties. An association between diet concerns and sleep difficulties was less consistent. Regression analyses showed that bulimic behaviour (BB) and social pressure to eat (SPE) dimensions were associated significantly with sleep difficulties (DIS, DMS, SDI) in the total sample (BB: from P<0.01 to P<0.001; SPE: P<0.05) and in males (BB: from P<0.05 to P<0.001; SPE: P<0.05) and with insomnia symptoms (P<0.01). In females, bulimic behaviour was the only factor associated significantly with sleep difficulties (SDI, DIS; P<0.01) and with insomnia symptoms (P<0.05). Although BMI was correlated negatively with sleep difficulties (P<0.05), regression analyses indicated that it was not associated significantly with them. Our findings support an association between eating behaviour and sleep disturbances in both genders, which may have treatment implications.

Obesity and shift work: chronobiological aspects

The present review has the objective of summarising chronobiological aspects of shift work and obesity. There was a systematic search in PubMed databases, using the following descriptors: shift work; obesity; biological clock. Shift work is extremely frequent in several services and industries, in order to systematise the needs for flexibility of the workforce, necessary to optimise productivity and business competitiveness. In developing countries, this population represents a considerable contingent workforce. Recently, studies showed that overweight and obesity are more prevalent in shift workers than day workers. In addition, the literature shows that shift workers seem to gain weight more often than those workers submitted to a usual work day. In conclusion, there is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes and CVD, perhaps as a result of physiological maladaptation to chronically sleeping and eating at abnormal circadian times. The impact of shift work on metabolism supports a possible pathway to the development of obesity and its co-morbities. The present review demonstrated the adverse cardiometabolic implications of circadian misalignment, as occurs chronically with shift workers.

Antagonism of T-type calcium channels inhibits high-fat diet-induced weight gain in mice

The epidemics of obesity and metabolic disorders have well-recognized health and economic burdens. Pharmacologic treatments for these diseases remain unsatisfactory with respect to both efficacy and side-effect profiles. Here, we have identified a potential central role for T-type calcium channels in regulating body weight maintenance and sleep. Previously, it was shown that mice lacking CaV3.1 T-type calcium channels have altered sleep/wake activity. We found that these mice were also resistant to high-fat diet-induced weight gain, without changes in food intake or sensitivity to high-fat diet-induced disruptions of diurnal rhythm. Administration of a potent and selective antagonist of T-type calcium channels, TTA-A2, to normal-weight animals prior to the inactive phase acutely increased sleep, decreased body core temperature, and prevented high-fat diet-induced weight gain. Administration of TTA-A2 to obese rodents reduced body weight and fat mass while concurrently increasing lean muscle mass. These effects likely result from better alignment of diurnal feeding patterns with daily changes in circadian physiology and potentially an increased metabolic rate during the active phase. Together, these studies reveal what we believe to be a previously unknown role for T-type calcium channels in the regulation of sleep and weight maintenance and suggest the potential for a novel therapeutic approach to treating obesity.

Dietary fat and sleep duration in Chinese men and women

BACKGROUND

Many recent studies have highlighted the complex interaction between sleep duration, food intake and metabolic balance. Although a causal link is yet to be established, emerging evidence suggests that short sleep duration may alter the balance between energy intake and energy expenditure. Thus far, most research has focussed on the link between sleep duration and carbohydrate metabolism. The role of sleep duration in fat intake and vice versa remains relatively unknown.

OBJECTIVE

The aim of this analysis was to determine whether there exists a significant association between sleep duration and fat intake.

DESIGN

Data from 2828 adults living in Jiangsu province, China, collected during a national survey of nutrition and health conducted in 2002.

RESULTS

The analysis showed a statistically significant association between sleep duration and fat and carbohydrate intake but not protein or fasting blood glucose. Those who slept for less than 7 h a day had significantly higher (P=0.005) percentage of energy from fat intake than those who slept for 7-9 h per day. Analysis of the influence of high fat intake upon sleep demonstrated a trend to reduced sleep duration between the highest and lowest quartiles of fat intake (P=0.056).

CONCLUSIONS

To our knowledge, this is the first data from a large cross-sectional study to show an association between decreased sleep duration and increased fat intake in humans. Given the trend towards decreased sleep duration in modern societies and the parallel obesity epidemic, the significance of this association warrants more research.