Sleep Extension: A Potential Target for Obesity Treatment

Intermittent Fasting: Socio-Economic Profile of Spanish Citizens Who Practice It and the Influence of This Dietary Pattern on the Health and Lifestyle Habits of the Population

Intermittent fasting (IF) is a dietary approach that has gained popularity in recent years. More and more Spanish people are following this eating pattern, which consists of alternating periods of fasting with periods of food intake. Its benefits include improved metabolic and vascular health and weight loss.

OBJECTIVES

1. To study the prevalence of IF among the Spanish population. 2. To explore how demographic factors influence the choice to adopt this dietary approach.

METHODS

A descriptive cross-sectional study was conducted on the Spanish population using the NutSo-HH questionnaire, which was constructed, validated, and disseminated by the research team through a non-probabilistic snowball sampling approach, collecting socio-demographic data and nutritional, social and lifestyle habits of the population.

RESULTS AND CONCLUSIONS

A valid sample of 22,181 people participated, of whom 4.59% (n = 1018) said they practiced IF. The data show that more middle-aged men than women practice IF. In addition, individuals who follow IF methods are less likely to have no control over their food intake, are less scared to gain weight and have a higher body image, but no differences were found related to unhealthy food and nights out. There were also no significant differences in terms of the level of education, income, size of municipality, or region of residence. In conclusion, a person who practices IF seems to have adopted a healthier lifestyle and social habits.

The association between sleep deprivation and the risk of cardiovascular diseases: A systematic meta‑analysis

Globally, sleep deprivation is a concerning health issue associated with an increased risk of cardiovascular diseases (CVDs). The present study aimed to explore the association between short-term sleep and the risk of CVDs, taking into consideration sex and age groups. A comprehensive review was conducted by assembling cohort studies that are available in the PubMed, Cochrane Library, and Embase databases. Individuals with ≤5 or ≤6 h of sleep per day were considered as sleep-deprived subjects. To minimize potential bias, two reviewers thoroughly evaluated the selected articles. Relevant data were extracted, and pooled odds ratios (ORs) or relative risks (RRs) were calculated using a random-effects model. In total, 18 cohort studies involving adult subjects were included in the present analysis. The pooled results strongly indicated that sleep deprivation was associated with a greater risk of CVDs [RR: 1.09, 95% confidence interval (CI): 1.02-1.16, P=0.009]. However, when the pooled analysis was stratified by sex and age, the following results were observed: short-term sleep women (RR: 1.06, 95% CI: 0.96-1.17, P=0.27), short-term sleep men (RR: 1.07, 95% CI: 0.97-1.17, P=0.17); ≥18 years-old sleep-deprived population (RR: 1.09, 95% CI: 1.00-1.17, P=0.04), ≥40 years-old sleep-deprived population (RR: 1.09, 95% CI: 0.98-1.22, P=0.11), and subjects with co-existing diseases, such as diabetes and hyperlipidemia (RR: 1.06, 95% CI: 0.94-1.20, P=0.32). In conclusion, short-term sleep is associated with the increased risk of CVDs. Among subjects who were aged ≥18 years-old, there was a strong association with the development of CVDs compared with those who were aged ≥40 years-old. Furthermore, men were at a higher risk of CVDs than women. Adequate sleep (7-8 h per day) may play a role in improving cardiac health. The results of the present study may provide valuable support for further research in public health, highlighting the correlation between sleep deprivation and the risk of CVDs.

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.

Sleep Deficiency and Cardiometabolic Disease

Epidemiologic studies have demonstrated that short sleep duration is associated with an increased risk of cardio-metabolic health outcomes including cardiovascular disease mortality, coronary heart disease, type 2 diabetes mellitus, hypertension, and metabolic syndrome. Experimental sleep restriction studies have sought to explain these findings. This review describes the main evidence of these associations and possible mechanisms explaining them. Whether sleep extension reverses these now widely acknowledged adverse health effects and the feasibility of implementing such strategies on a public health level is discussed.

Obesity: Heart Rate Variability during standardized psychosocial stress induction

Obesity is related to a higher risk of cardiovascular diseases (CVD). An altered stress reactivity of the parasympathetic nervous system (PNS) is a promising predictor of CVD and other negative health outcomes. Therefore, the aim of this study was to compare heart rate (HR) and heart rate variability parameters, root mean square successive differences (RMSSD) and power in the high frequency range 0.15-0.4 Hz (HF-HRV), of individuals with obesity and healthy weight controls during psychosocial stress induction. Thirty-four obese men and women (BMI: 33.80 ± 4.62 kg/m²), and thirty-four age- and gender-matched healthy weight controls (BMI: 22.29 ± 1.81 kg/m²) underwent the Trier Social Stress Test (TSST). Before, during, and after the TSST, their HR, RMSSD, and HF-HRV were measured. The individuals with obesity showed a lower stress reactivity in HR, and less stress recovery in RMSSD, compared to healthy weight controls. Obesity appears related to blunted HR reactivity, which is associated with CVD. In addition, impaired recovery of RMSSD also found in individuals with obesity may reflect health-damaging processes as well.

Insufficient Sleep Syndrome: A Blind Spot in Our Vision of Healthy Sleep

Chronic sleep deficiency (CSD) poses a threat to physical health, mental well-being, and social functioning. The concept of behaviorally induced CSD has not changed much since it was first introduced four decades ago. Behaviorally induced CSD is currently referred to as insufficient sleep syndrome (ISS). In the latest edition of the International Classification of Sleep Disorders (ICSD-3, 2014), ISS is considered a disorder of central hypersomnolence with diagnostic codes ICD-9-CM 307.44 and ICD-10-CM F51.12. In this review, we will describe the biological importance of sleep, the ramifications of CSD on the individual and society, the nosological status and diagnostic features of ISS, and the apparent lack of attention to ISS in contemporary medical practice and public health programs. The last three decades have seen a global rise in voluntary sleep curtailment such that ISS may already be the leading cause of CSD, not only in adults but also in school-aged children and adolescents. Acknowledging ISS as a public health priority is a necessary first step in our response to the global threat of CSD and CSD-related health consequences. It is only by confronting ISS directly that we can hope to develop and implement effective educational and advocacy programs, along with more responsible public health policies and regulations.

Associations between sleep duration and cardiovascular diseases: A meta-review and meta-analysis of observational and Mendelian randomization studies

The associations between sleep duration and cardiovascular diseases (CVDs) have been explored in many observational studies. However, the causality of sleep duration and many CVDs, such as coronary artery disease (CAD), heart failure (HF), and stroke, remains unclear. In this study, we conducted a systematic meta-review and meta-analysis of the results of observational and Mendelian randomization (MR) studies to examine how sleep duration impacts the risk of CVDs. We searched articles published in English and before 10 September 2021 in PubMed, Web of Science, and Embase. The articles were screened independently by two reviewers to minimize potential bias. We combined the meta-analyses of observational studies and 11 MR studies and summarized evidence of the effect of sleep duration on the risk of CAD, HF, stroke, and cardiovascular and all-cause mortality. Results showed that (a) evidence is accumulating that short sleep duration is a causal risk factor for CAD and HF; (b) abundant evidence from observational studies supports that long sleep duration is associated with the risk of CAD, stroke, and mortality, and long sleep duration has no causal associations with stroke and CAD in the MR studies; the causation of long sleep duration and other CVDs should be further studied; and (c) emerging evidence indicates that an increase in hours of sleep is associated with a decreased risk of CAD. Finally, we discussed the underlying pathophysiological mechanisms underlying short sleep duration and CVDs and suggested that increasing sleep duration benefits cardiovascular health.

Sleep Deficiency and Cardiometabolic Disease

Epidemiologic studies have demonstrated that short sleep duration is associated with an increased risk of cardio-metabolic health outcomes including cardiovascular disease mortality, coronary heart disease, type 2 diabetes mellitus, hypertension, and metabolic syndrome. Experimental sleep restriction studies have sought to explain these findings. This review describes the main evidence of these associations and possible mechanisms explaining them. Whether sleep extension reverses these now widely acknowledged adverse health effects and the feasibility of implementing such strategies on a public health level is discussed.

Sleep Duration and Hypertension: Epidemiological Evidence and Underlying Mechanisms

While the contribution of several physiological systems to arterial blood pressure regulation has been studied extensively, the role of normal and disrupted sleep as a modifiable determinant of blood pressure control, and in the pathophysiology of hypertension, has only recently emerged. Several sleep disorders, including sleep apnea and insomnia, are thought to contribute to the development of hypertension, although less attention is paid to the relationship between sleep duration and blood pressure independent of sleep disorders per se. Accordingly, this review focuses principally on the physiology of sleep and the consequences of abnormal sleep duration both experimentally and at the population level. Clinical implications for patients with insomnia who may or may not have abbreviated sleep duration are explored. As a corollary, we further review studies of the effects of sleep extension on blood pressure regulation. We also discuss epidemiological evidence suggesting that long sleep may also be associated with hypertension and describe the parabolic relationship between total sleep time and blood pressure. We conclude by highlighting gaps in the literature regarding the potential role of gut microbial health in the cross-communication of lifestyle patterns (exercise, diet, and sleep) with blood pressure regulation. Additionally, we discuss populations at increased risk of short sleep, and specifically the need to understand mechanisms and therapeutic opportunities in women, pregnancy, the elderly, and in African Americans.

Intermittent Fasting and Sleep: A Review of Human Trials

This review examines the effects of two popular intermittent fasting regimens on sleep in adults with overweight and obesity. Specifically, the effects of time restricted eating (TRE; eating all food within a 4-10 h window) and alternate day fasting (ADF; 600 kcal fast day alternated with ad libitum feast day) on sleep quality, sleep duration, sleep latency, sleep efficiency, insomnia severity, and risk of obstructive sleep apnea, will be summarized. The role of weight loss will also be discussed. Results from our review reveal that the majority of these trials produced weight loss in the range of 1-6% from baseline. Sleep quality and sleep duration remained unaltered with TRE and ADF, as assessed by the Pittsburgh Sleep Quality Index (PSQI). The effects of intermittent fasting on sleep latency and sleep efficiency are mixed, with one study showing worsening of these parameters, and others showing no effect. Insomnia severity and the risk of obstructive sleep apnea remained unchanged in the trials assessing these metrics. Taken together, these preliminary findings suggest that TRE and ADF produce mild to moderate weight loss (1-6%) but their effects on sleep remain unclear. Solid conclusions are difficult to establish since participants in the studies had healthy sleep durations and no clinical insomnia at baseline, leaving little room for improvement in these metrics. Moreover, none of the trials were adequately powered to detect statistically significant changes in any measure of sleep. Future well-powered trials, conducted in individuals with diagnosed sleep disturbances, will be necessary to elucidate the effect of these popular diets on sleep.

Metabolic Disturbances Induced by Sleep Restriction as Potential Triggers for Alzheimer's Disease

Sleep has a major role in learning, memory consolidation, and metabolic function. Although it is known that sleep restriction increases the accumulation of amyloid β peptide (Aβ) and the risk to develop Alzheimer's disease (AD), the mechanism behind these effects remains unknown. In this review, we discuss how chronic sleep restriction induces metabolic and cognitive impairments that could result in the development of AD in late life. Here, we integrate evidence regarding mechanisms whereby metabolic signaling becomes disturbed after short or chronic sleep restriction in the context of cognitive impairment, particularly in the accumulation of Aβ in the brain. We also discuss the role of the blood-brain barrier in sleep restriction with an emphasis on the transport of metabolic signals into the brain and Aβ clearance. This review presents the unexplored possibility that the alteration of peripheral metabolic signals induced by sleep restriction, especially insulin resistance, is responsible for cognitive deficit and, subsequently, implicated in AD development.

Considerations for Maximizing the Exercise "Drug" to Combat Insulin Resistance: Role of Nutrition, Sleep, and Alcohol

Insulin resistance is a key etiological factor in promoting not only type 2 diabetes mellitus but also cardiovascular disease (CVD). Exercise is a first-line therapy for combating chronic disease by improving insulin action through, in part, reducing hepatic glucose production and lipolysis as well as increasing skeletal muscle glucose uptake and vasodilation. Just like a pharmaceutical agent, exercise can be viewed as a "drug" such that identifying an optimal prescription requires a determination of mode, intensity, and timing as well as consideration of how much exercise is done relative to sitting for prolonged periods (e.g., desk job at work). Furthermore, proximal nutrition (nutrient timing, carbohydrate intake, etc.), sleep (or lack thereof), as well as alcohol consumption are likely important considerations for enhancing adaptations to exercise. Thus, identifying the maximal exercise "drug" for reducing insulin resistance will require a multi-health behavior approach to optimize type 2 diabetes and CVD care.

Alternate Day Fasting Combined with a Low Carbohydrate Diet: Effect on Sleep Quality, Duration, Insomnia Severity and Risk of Obstructive Sleep Apnea in Adults with Obesity

Background: Alternate day fasting combined with a low carbohydrate diet (ADF-LC) is an effective weight loss regimen. Whether the weight loss induced by ADF-LC can improve sleep, remains unknown. Objective: This study examined the effect an ADF-LC diet on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea. Methods: Adults with obesity (n = 31) participated in ADF (600 kcal “fast day”; ad libitum intake “feast day”) with a low-carbohydrate diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period. Results: Reductions in body weight (−5 ± 1 kg, p < 0.001) and fat mass (−4 ± 1 kg, p < 0.01) were noted during the weight loss period, and these reductions were sustained during the weight maintenance period. Lean mass and visceral fat remained unchanged. The Pittsburgh Sleep Quality Index (PSQI) score indicated poor sleep quality at baseline (6.4 ± 0.7) with no change by month 3 or 6, versus baseline. ISI score indicated subthreshold insomnia at baseline (8.5 ± 1.0), with no change by month 3 or 6, versus baseline. The percent of subjects with high risk of obstructive sleep apnea at baseline was 45%, with no change by month 3 or 6. Wake time, bedtime, and sleep duration remained unchanged. Conclusion: The ADF-LC diet does not impact sleep quality, duration, insomnia severity or the risk of obstructive sleep apnea in adults with obesity.