Factors associated with changes in walking performance in individuals 3 months after stroke or TIA: secondary analyses from a randomised controlled trial of SMS-delivered training instructions in Sweden

OBJECTIVES

This study aimed to identify factors related to changes in walking performance in individuals 3 months after a stroke or TIA.

DESIGN

Cross-sectional study with post hoc analysis of a randomised controlled study.

SETTING

University Hospital, Sweden.

PARTICIPANTS

79 individuals, 64 (10) years, 37% women, who were acutely hospitalised because of stroke or TIA between November 2016 and December 2018. Inclusion criteria were patients aged 18 or above and the major eligibility criterion was the ability to perform the 6 min walking test.

INTERVENTION

The intervention group received standard care plus daily mobile phone text messages (short message service) with instructions to perform regular outdoor walking and functional leg exercises in combination with step counting and training diaries. The control group received standard care.

OUTCOME MEASURES

Multivariate analysis was performed and age, sex, group allocation, comorbidity, baseline 6 min walk test, body mass index (BMI), cognition and chair-stand tests were entered as possible determinants for changes in the 6 min walk test.

RESULTS

Multiple regression analyses showed that age (standardised beta -0.33, 95% CI -3.8 to -1.05, p<0.001), sex (-0.24, 95% CI -66.9 to -8.0, p=0.014), no comorbidity (-0.16, 95% CI -55.5 to 5.4, p=0.11), baseline BMI (-0.29, 95% CI -8.1 to -1.6, p=0.004), baseline 6 min walk test (-0.55, 95% CI -0.5 to -0.3, p<0.001) were associated with changes in 6 min walk test 3 months after the stroke event. The regression model described 36% of the variance in changes in the 6 min walk test.

CONCLUSIONS

Post hoc regression analyses indicated that younger age, male sex, lower BMI and shorter 6 min walk test at baseline and possible no comorbidity contributed to improvement in walking performance at 3 months in patients with a recent stroke or TIA. These factors may be important when planning secondary prevention actions.

TRIAL REGISTRATION NUMBER

NCT02902367.

Effects of a novel weight-loss combination product containing orlistat and acarbose on obesity: A randomized, placebo-controlled trial

OBJECTIVE

The aim of this study was to evaluate the effect of a novel, oral, modified-release formulation of the lipase inhibitor orlistat and the glucosidase/amylase inhibitor acarbose (denoted EMP16) on relative body weight after 26 weeks compared with placebo.

METHODS

The randomized, double-blind, placebo-controlled trial had a 26-week treatment period, with dose escalation up to 6 weeks. Participants, adults between ages 18 and 75 years, with BMI ≥30 kg/m² or ≥28 kg/m² with risk factors, were randomly assigned to EMP16 120-mg orlistat/40-mg acarbose (EMP16-120/40), EMP16-150/50, or placebo. The primary end point was relative weight loss from baseline to week 26 assessed in participants with at least one post-baseline weight measurement.

RESULTS

Of 156 randomized participants, 149 constituted the intention-to-treat population. The mean (95% CI) estimated treatment difference to placebo in relative weight loss after 26 weeks in the intention-to-treat population was -4.70% (-6.16% to -3.24%; p < 0.0001) with EMP16-120/40 and -5.42% (-6.60% to -4.24%; p < 0.0001) with EMP16-150/50.

CONCLUSIONS

This trial indicates that orlistat and acarbose can be successfully combined in a modified-release formulation to provide efficacious weight loss with no unexpected safety issues. EMP16 may be a promising candidate among other medications for improved weight management.

Safety of a Novel Weight Loss Combination Product Containing Orlistat and Acarbose

The safety of a novel modified‐release oral capsule with orlistat and acarbose (MR‐OA) was investigated in 67 obese middle‐aged White men with a body mass index of 32 to 40 kg/m² or 30 to 32 kg/m² plus waist circumference >102 cm. The purpose of this investigation was to compare MR‐OA with the existing conventional orlistat regarding systemic safety defined as plasma orlistat concentration at the end of the treatment period of 14 days. Participants took the MR‐OA fixed‐dose combination formulation 3 times a day together with a major meal. Three different doses of MR‐OA were evaluated—60/20, 90/30, and 120/40 (mg orlistat/mg acarbose)—as well as 1 reference group who received the conventional orlistat, Xenical, with 120 mg of orlistat. Blood plasma was sampled on days 1 and 14. The orlistat plasma concentrations of the MR‐OA dose showed a delayed absorption and were lower compared with conventional orlistat at the end of the study. All doses were safe and well tolerated without any unexpected adverse events and no serious adverse events. The delay in the rise of orlistat plasma concentration indicates that the modified‐release properties of the MR‐OA formulation are effective. The systemic exposure of orlistat resulting from MR‐OA was similar, albeit a bit lower than the conventional orlistat with 120 mg of orlistat. We can therefore assume that the safety profile regarding the orlistat moiety of MR‐OA is comparable to the conventional orlistat and a promising approach for weight control in obese patients. Further clinical evaluation is underway.

Effects on walking performance and lower body strength by short message service guided training after stroke or transient ischemic attack (The STROKEWALK Study): a randomized controlled trial

OBJECTIVE

To evaluate whetherdaily mobile-phone delivered messages with training instructions during three months increase physical activity and overall mobility in patients soon after stroke or transient ischemic attack.

DESIGN

Randomised controlled trial with intention-to-treat analyses.

SETTING

University hospital. Data collection from November 2016 until December2018.

SUBJECTS

Seventy-nine patients (mean (SD) age 63.9 (10.4) years, 29 were women) were allocated to either intervention (n = 40) or control group (n = 39). Participants had to be independent (modified Ranking Scale ⩽2) and able to perform the six-minute walking test at discharge from the hospital.

INTERVENTIONS

The intervention group received standard care and daily mobile phone instructional text messages to perform regular outdoor walking and functional leg exercises. The control group received standard care; that is, primary care follow-up.

MAIN MEASURES

Walking performance by six-minute walking test (m), lower body strength by five times chair-stand test (s), the short physical performance battery (0-12 points) and 10-metres walk test (m/s) were assessed at baseline and after three months.

RESULTS

The estimated median difference in the six-minute walking test was in favour of the intervention group by 30 metres (95% CI, 55 to 1; effect size 0.64; P = 0.037) and in the chair-stand test by 0.88 seconds (95% CI, 0.02 to 1.72; effect size 0.64; P = 0.034). There were no differences between groups on the short physical performance battery or in 10-metres walking time.

CONCLUSIONS

Three months of daily mobile phone text messages with guided training instructions improved composite mobility measures; that is, walking performanceand lower body strength.

CLINICAL TRIAL REGISTRY

The study is registered with ClinicalTrials.gov, number NCT02902367.

Effects of a novel combination of orlistat and acarbose on tolerability, appetite, and glucose metabolism in persons with obesity

Objective

There is an unmet medical need for a safe and effective weight loss product with minimal systemic side‐effects. In this study, the effect of a novel modified‐release fixed‐dose combination of orlistat and acarbose (MR‐OA) was compared with conventional orlistat (CO) regarding tolerability, appetite and glucose metabolism.

Methods

Sixty‐seven men with obesity, aged 24 to 60 years with body mass indexes (BMIs) 33 to 40 kg m⁻² or BMIs 30 to 32 kg m⁻² and waist circumference above 102 cm were included. They were randomized to either three different doses of the test formulation MR‐OA (60 mg orlistat/20 mg acarbose, 90/30 and 120/40) or CO (Xenical, 120 mg orlistat) for a 2‐week study of daily treatment. The participants spent days 1 and 14 at the clinical research centre where they received standardized meals, had blood sampling and filled in questionnaires regarding tolerability and appetite after meals. In days 2 to 13, the participants were at home and continued to fill in the questionnaires daily.

Results

In the MR‐OA groups, reports of liquid and oily stools as well as faecal incontinence were fewer, whereas reports of gastric distension and flatulence were higher, compared with the CO group. More participants reported decreased hunger in the 90/30 and 120/40 MR‐OA, and postprandial plasma glucose concentration was reduced in all MR‐OA groups compared with CO.

Conclusions

This study shows that by using a modified‐release dosage form, orlistat and acarbose can be combined without compromising tolerability. Furthermore, MR‐OA shows promising effects regarding reduction of appetite and reduces postprandial glucose. Tolerability is coupled to compliance and thereby efficacy of a treatment; therefore, this novel combination MR‐OA could be an effective approach for weight loss treatment. A follow‐up study in a more diverse population and for a longer duration with weight loss as primary outcome variable is planned.

Preserved Fat-Free Mass after Gastric Bypass and Duodenal Switch

Background

Concerns for the possibility of an excessive loss of fat-free mass (FFM) and resting metabolic rate (RMR) after bariatric surgery, such as Roux-en-Y gastric bypass (RYGB) and duodenal switch (BPD/DS), have been raised.

Objectives

This study aims to examine body composition and RMR in patients after RYGB and BPD/DS and in non-operated controls.

Methods

Body composition and RMR were studied with Bod Pod and indirect calorimetry in weight-stable RYGB (n = 15) and BPD/DS patients (n = 12) and compared with non-operated controls (n = 17). All patients were 30–55 years old and weight stable with BMI 28–35 kg/m².

Results

FFM% was 58% (RYGB), 61% (BPD/DS), and 58% (controls). Body composition did not differ after RYGB and BPD/DS compared to controls, despite 27 and 40% total body weight loss, respectively. No difference in RMR or RMR/FFM was observed (1539, 1617, and 1490 kcal/24 h; and 28.9, 28.4, and 28.8 kcal/24 h/kg).

Conclusion

Weight-stable patients with BMI 28–35 kg/m² after RYGB and BPD/DS have a body composition and RMR similar to that of non-operated individuals within the same BMI interval.

Subjective and objective assessment of physical activity - Influence of newly diagnosed exercise induced bronchoconstriction and gender

AIM

To investigate if occurrence of newly diagnosed exercise induced bronchoconstriction (EIB) would affect adolescents' ability to assess their physical activity.

METHODS

99 selected adolescents with and 47 adolescents without self-reported exercise induced dyspnea were included. All of the 146 adolescents then performed a standardized exercise challenge test on a treadmill with dry-air inhalation to detect EIB. Free living physical activity was assessed during seven days with both accelerometer (objective assessment) and a validated activity diary (subjective assessment). Height, weight and subjective sleep were recorded.

RESULTS

Out of the 146 adolescents 49 were diagnosed with EIB. Forty-six of the adolescents with EIB (35 girls and 11 boys) and 84 of the control adolescents (45 girls and 39 boys) had complete 7 day activity diary and accelerometer data. There were no differences in age, BMI and sleep between EIB and control adolescents. Boys with EIB overestimated subjective assessment compared to objective assessment more than girls with EIB. No difference was seen between control boys and girls. Furthermore, boys with EIB reported a much higher frequency of high intensity exercise than girls with EIB, but no difference was observed between control boys and girls.

CONCLUSION

Adolescent boys with newly diagnosed EIB overestimated their physical activity compared to EIB girls. Caution may thus be used when choosing methods measuring level of physical activity in this group and especially when investigating gender differences.

Children with cerebral palsy do not achieve healthy physical activity levels

AIM

This study compared daily activity energy expenditure (AEE) in children with cerebral palsy with a control group and investigated whether the children achieved healthy levels of physical activity.

METHODS

We enrolled eight children with bilateral cerebral palsy, from eight to 10 years of age, and a group of controls matched for age and gender. For three days, physical activity was simultaneously measured by accelerometers and self-reports using a diary. The daily AEE results were compared between groups and methods. The number of children that achieved healthy physical activity levels in each group was explored.

RESULTS

Children with cerebral palsy had significantly lower daily AEE, as measured by accelerometers, than the controls, and they did not achieve the healthy moderate to heavy physical activity level defined in the Nordic Nutrition Recommendations. Self-reports using the diaries resulted in an overestimation of physical activity compared with the ankle accelerometer measurements in both groups.

CONCLUSION

Our investigation of physical activity in children with cerebral palsy and controls using accelerometers and a diary found low levels of daily AEE and physical activity, and these results were most prominent in the group with cerebral palsy. The diaries overestimated physical activity in both groups.

Circadian misalignment augments markers of insulin resistance and inflammation, independently of sleep loss

Shift workers, who are exposed to irregular sleep schedules resulting in sleep deprivation and misalignment of circadian rhythms, have an increased risk of diabetes relative to day workers. In healthy adults, sleep restriction without circadian misalignment promotes insulin resistance. To determine whether the misalignment of circadian rhythms that typically occurs in shift work involves intrinsic adverse metabolic effects independently of sleep loss, a parallel group design was used to study 26 healthy adults. Both interventions involved 3 inpatient days with 10-h bedtimes, followed by 8 inpatient days of sleep restriction to 5 h with fixed nocturnal bedtimes (circadian alignment) or with bedtimes delayed by 8.5 h on 4 of the 8 days (circadian misalignment). Daily total sleep time (SD) during the intervention was nearly identical in the aligned and misaligned conditions (4 h 48 min [5 min] vs. 4 h 45 min [6 min]). In both groups, insulin sensitivity (SI) significantly decreased after sleep restriction, without a compensatory increase in insulin secretion, and inflammation increased. In male participants exposed to circadian misalignment, the reduction in SI and the increase in inflammation both doubled compared with those who maintained regular nocturnal bedtimes. Circadian misalignment that occurs in shift work may increase diabetes risk and inflammation, independently of sleep loss.

Acute Sleep Restriction Reduces Insulin Sensitivity in Adolescent Boys

BACKGROUND

Short sleep duration has been linked to impaired glucose metabolism in many experimental studies. Moreover, studies have reported indications of an increased metabolic stress following sleep restriction.

OBJECTIVE

We aimed to investigate the effects of partial sleep deprivation on markers of glucose metabolism. Additionally, we aimed to investigate if short sleep duration induces a state of endocrine stress.

DESIGN

A randomized crossover design, with 2 experimental conditions: 3 consecutive nights of short sleep (SS, 4 h/night) and long sleep (LS, 9 h/night) duration.

SUBJECTS AND MEASUREMENTS

In 21 healthy, normal-weight male adolescents (mean ± SD age: 16.8 ± 1.3 y) we measured pre- and post-prandial glucose, insulin, C-peptide, and glucagon concentrations. Furthermore, we measured fasting cortisol, 24-h catecholamines, and sympathovagal balance.

RESULTS

Fasting insulin was 59% higher (P = 0.001) in the SS than the LS condition as was both fasting (24%, P < 0.001) and post-prandial (11%, P = 0.018) C-peptide. Pre- and post-prandial glucose and glucagon were unchanged between conditions. The homeostasis model assessment of insulin resistance (HOMA-IR) index was 65% higher (P = 0.002) and the Matsuda index was 28% lower (P = 0.007) in the SS condition compared to the LS condition. The awakening cortisol response and 24-h norepinephrine were not affected by sleep duration, whereas 24-h epinephrine was 24% lower (P = 0.013) in the SS condition. Neither daytime nor 24-h sympathovagal balance differed between sleep conditions. Short wave sleep was preserved in the SS condition.

CONCLUSION

Short-term sleep restriction is associated with decreased insulin sensitivity in healthy normal-weight adolescent boys. There were no indications of endocrine stress beyond this.

CITATION

Klingenberg L; Chaput JP; Holmbäck U; Visby T; Jennum P; Nikolic M; Astrup A; Sjödin A. Acute Sleep Restriction Reduces Insulin Sensitivity in Adolescent Boys. SLEEP 2013;36(7):1085-1090.

Ghrelin and obestatin in human neuroendocrine tumors: expression and effect on obestatin levels after food intake

BACKGROUND

Ghrelin and obestatin are derived from the same peptide hormone precursor and are mainly produced by the gastric mucosa. Ghrelin is involved in many biological processes, whereas the physiological function of obestatin needs further investigation. The aims of the present study were to establish the incidence of ghrelin- and obestatin-immunoreactive cells in a comprehensive panel of human neuroendocrine tumors (NETs) and to investigate if blood obestatin concentrations are influenced during a standardized meal stimulation test in healthy individuals and patients with NETs.

MATERIALS AND METHODS

The expression of ghrelin and obestatin was investigated in NETs (n = 149) and other endocrine-related disorders (n = 3) using immunohistochemistry with specific polyclonal antibodies. Coexpression of the peptides was evaluated by double immunofluorescence. Concentrations of obestatin in blood were measured during a meal test in 6 healthy individuals and 5 patients with pancreatic NETs.

RESULTS

Ghrelin and obestatin were expressed in 14/152 and 19/152 tumor tissues, respectively, mainly representing NETs of foregut origin and in pancreatic tissue from a nesidioblastosis patient. Double immunofluorescence staining showed colocalization of the peptides. During the meal test, obestatin levels in blood were unchanged in all patients but decreased significantly in the healthy individuals.

CONCLUSION

Only a minority of NETs express ghrelin and obestatin. However, analysis of patients with tumors originating from tissues that express the peptides in normal conditions could be of importance. The results from the meal test indicate that the hormone levels are affected by food intake in healthy individuals, whereas obestatin levels remained unchanged in pancreatic NET patients.

Sleep restriction is not associated with a positive energy balance in adolescent boys

BACKGROUND

A short sleep (SS) duration has been linked to obesity in observational studies. However, experimental evidence of the potential mechanisms of sleep restriction on energy balance is conflicting and, to our knowledge, nonexistent in adolescents.

OBJECTIVE

We investigated the effects of 3 consecutive nights of partial sleep deprivation on components of energy balance.

DESIGN

In a randomized, crossover design, 21 healthy, normal-weight male adolescents (mean ± SD age: 16.8 ± 1.3 y) completed the following 2 experimental conditions, each for 3 consecutive nights: an SS (4 h/night) and a long sleep (LS; 9 h/night) duration. Endpoints were 24-h energy expenditure (EE), spontaneous physical activity (SPA), postintervention diet-induced thermogenesis (DIT), appetite sensations, ad libitum energy intake (EI), and profiles of plasma ghrelin and leptin.

RESULTS

The 24-h EE on day 3 was 370 ± 496 kJ higher in the SS condition than in the LS condition (P = 0.003). This difference in EE was explained by prolonged wakefulness in the SS condition and a 19% higher SPA (P = 0.003). In a postintervention breakfast-meal challenge, there was a 0.19-kJ/min smaller incremental AUC in DIT over 4 h in the SS condition than in the LS condition (P = 0.012) with no time × condition effect (P = 0.29). Subjects consumed 13% less energy in the ad libitum meal in the SS condition (P = 0.031), with a concomitant decreased motivation to eat. Concentrations of ghrelin and leptin remained unchanged with sleep restriction.

CONCLUSION

Short-term sleep restriction in male adolescents is associated with a small negative energy balance driven by increased EE from prolonged wakefulness and a concomitant decreased EI and motivation to eat. This trial was registered at clinicaltrials.gov as NCT01198431.

Short sleep duration and its association with energy metabolism

A growing body of observational evidence suggests that short sleep duration is a risk factor for the development of obesity. Although increased energy intake is the most prevailing causal explanation for this association, we should also consider possible effects on energy metabolism to understand fully the potential impact of short sleep duration on the regulation of energy balance. We performed a search of the literature from 1970 to 2011, including original papers, investigating the relation between short sleep and energy metabolism in animals and humans. Although the limited number of experimental studies in humans precludes any definitive conclusions about causality, short sleep duration does not seem to substantially affect total daily energy expenditure, nor is there sufficient evidence in support of any meaningful effect of restricted sleep on the specific components of energy metabolism (i.e. resting metabolic rate, intentional as well as unintentional physical activity, diet-induced thermogenesis, and substrate utilization). As studies on rats suggest that other factors that can potentially influence energy metabolism could be affected (i.e. hormonal systems and thermoregulation), we included these factors in our literature search and found some indications in support of an up-regulation of thyroid hormones and glucocorticoids as well as increased heat dissipation following total or severe sleep deficit. Although we found some evidence also in humans that suggests a possible effect on energy metabolism, the limitations of the studies make it difficult to draw conclusions on the effect of short sleep on energy metabolism under relevant free living conditions. To explore this area further, more studies using suitable methodology under relevant conditions to mimic real-life situations are needed.

Sleeping during the day: effects on the 24-h patterns of IGF-binding protein 1, insulin, glucose, cortisol, and growth hormone

BACKGROUND

Disturbed sleep is a major risk factor for metabolic disturbances, including type 2 diabetes, but the involved mechanisms are still poorly understood. We investigated how an acute shift of sleep to the daytime affected IGF-binding protein 1 (IGFBP1), which is a risk factor for diabetes.

METHODS

Seven healthy men (age, 22-32 years) participated in a night sleep condition (sleep 2300-0700 h) and a day sleep condition (0700-1500 h) with hourly blood samples taken for 25 h (starting at 1900 h) and isocaloric meals every 4th hour awake. The blood samples were analyzed for IGFBP1, insulin, GH, glucose, and cortisol.

RESULT

The acute shift of sleep and meal timing (to 8 h) shifted the 24-h patterns of IGFBP1, glucose, insulin, and GH to a similar degree. However, the day sleep condition also resulted in elevated levels of IGFBP1 (area under curve (AUC)+22%, P<0.05), and reduced glucose levels (AUC-7%, P<0.05) compared with nocturnal sleep. Sleeping during the day resulted in elevated cortisol levels during early sleep and reduced levels in late sleep, but also in increased levels the subsequent evening (P's<0.05).

CONCLUSION

Sleep-fasting seems to be the primary cause for the elevation of IGFBP1, irrespective of sleep timing. However, sleeping during the day resulted in higher levels of IGFBP1 than nocturnal sleep, suggesting altered metabolism among healthy individuals, which may have implications for other groups with altered sleep/eating habits such as shift workers. Moreover, sleep and meal times should be accounted for while interpreting IGFBP1 samples.

Eating and shift work - effects on habits, metabolism and performance

Compared to individuals who work during the day, shift workers are at higher risk of a range of metabolic disorders and diseases (eg, obesity, cardiovascular disease, peptic ulcers, gastrointestinal problems, failure to control blood sugar levels, and metabolic syndrome). At least some of these complaints may be linked to the quality of the diet and irregular timing of eating, however other factors that affect metabolism are likely to play a part, including psychosocial stress, disrupted circadian rhythms, sleep debt, physical inactivity, and insufficient time for rest and revitalization. In this overview, we examine studies on food and nutrition among shift workers [ie, dietary assessment (designs, methods, variables) and the factors that might influence eating habits and metabolic parameters]. The discussion focuses on the quality of existing dietary assessment data, nutritional status parameters (particularly in obesity), the effect of circadian disruptions, and the possible implications for performance at work. We conclude with some dietary guidelines as a basis for managing the nutrition of shift workers.

Overweight more prevalent among children than among adolescents

AIMS

To study if there is a change in paediatric overweight/obesity prevalence from 1982 to 2002 in a population with a high proportion of post-graduate education.

DESIGN

Two samples of children in Uppsala County, Sweden, were compared: children who were 4, 10 and 16 year old in 1982; or 4, 10 and 16 year old in 2002. Mean BMI (in the lowest 10%, middle 50% and highest 10%) and ISO-BMI ('age adjusted BMI') cut-off values were calculated in each age and gender group.

RESULTS

Using the mean BMI or ISO-BMI cut-off values, the BMI-distribution shifted from 1982 to 2002. More 4- and 10-year-old girls and boys were overweight/obese, although this shift was larger in girls. No shift was seen in the 16-year-olds, only the middle 50% group in the 16-year-old girls had a slight increase of their mean BMI. In the 2002 4-year-old, and both 10-year-old samples, a higher proportion of the girls were overweight/obese compared to the boys, but no difference was seen in the 16-year-old sample.

CONCLUSION

Young children, especially girls, have become much more overweight/obese during the past 20 years, despite a high proportion of post-graduate education in the population. The lack of major change in 16-year-olds may suggest a rather recent change in the children's environment/lifestyle.

Minor changes in blood lipids after 6 weeks of high-volume low- intensity physical activity with strict energy balance control

Physical activity has been shown to favorably affect metabolic risk markers, including blood lipids. The impact of high-energy turnover, without influencing the traditionally used markers of exercise training effects, on blood lipids is still unclear. The aim was to study the effect of high-volume low-intensity physical activity on the blood lipid pattern, with a tight control of diet and energy balance. Eight untrained men [42.5 (12.1) years, body mass index 24.2 (2.8) kg m(-2)] were tested in two different 6-week protocols. In the sedentary protocol, the subjects were instructed to limit their everyday physical activity. In the activity protocol, a 2-h physical activity bout was performed 5 days week(-1) (approximately 40% of VO(2max); equivalent of an additional 21 MJ week(-1) in energy expenditure). The diet for both protocols comprised approximately 40 energy percent (E%) fat, approximately 50 E% carbohydrates (CHO). The polyunsaturated fatty acids to saturated fatty acids ratio of the diet was approximately 0.12. There were no changes during each 6-week period or differences between the two protocols in body weight, body composition or aerobic capacity. Low-intensity physical activity did not affect lipid parameters substantially, except for a slightly lower Apo-B/Apo-A1 ratio with the activity protocol (P < 0.05). Total and low-density lipoprotein cholesterol, as well as Apo-B and Apo-A1, were increased during the beginning of each 6-week period (P < 0.05), but returned to basal levels by the sixth week. In conclusion, 6 weeks of high-volume low-intensity physical activity did not affect blood lipids substantially.

Effects of acutely displaced sleep on testosterone

CONTEXT

It is not yet clear whether the diurnal variation in testosterone is regulated by circadian or homeostatic (sleep) influences.

OBJECTIVE

The present study tested whether testosterone is driven by a circadian-independent sleep effect by shifting sleep acutely to daytime in a 24-h sampling regiment.

DESIGN, SETTING, AND PARTICIPANTS

In the sleep laboratory, seven healthy young men (age, 22-32 yr) participated in three conditions: habituation (sleep between 2300-0700 h), night sleep (2300-0700 h), and day sleep (0700-1500 h), the latter two in a balanced order.

INTERVENTION AND MAIN OUTCOME MEASURE

Serum testosterone was, in all conditions, sampled by hourly blood drawing for 24 h during constant bed rest.

RESULTS

Mean testosterone levels increased as a log-linear function of time (hours) across both sleep periods (b = 4.88; P < 0.001), from 15.3 +/- 2.1 to 25.3 +/- 2.2 nmol/liter during night sleep and from 17.3 +/- 2.1 to 26.4 +/- 2.9 nmol/liter during day sleep. Similarly, mean testosterone levels decreased with time (log-linear) awake (b = -1.80; P < 0.001). There was also evidence of a weak circadian component (acrophase ranging between 0651-0924 h) and an increase with time in the laboratory. Moreover, all these effects, except for the increase during sleep, differed significantly between individuals.

CONCLUSION

In conclusion, testosterone increased during sleep and fell during waking, whereas circadian effects seemed marginal. Individual differences were pronounced.

Increased VLDL-TAG Turnover during and after Acute Moderate-Intensity Exercise

PURPOSE AND METHODS

Breakdown rates of very low density lipoprotein triacylglycerols (VLDL-TAG) were quantified before (3 h), during (45 min), and after (3 h) moderate physical exercise at 40% VO2 max in young sedentary subjects (four male and four female, age 29.8 +/-1.6 yr, BMI 24.1 +/- 0.9 kg x m, VO2max 37.0 +/- 1.7 mL x kg x min), using boluses of H5-glycerol (100 mu mol x kg) and H2-palmitate (6.6 mu mol x kg). The catabolic rates of VLDL-TAG were calculated from the decay in the isotopic enrichment using a single-pool model. The results were compared with those obtained during 6 h of rest in five of the same volunteers.

RESULTS

VLDL-TAG concentration remained constant throughout the study with exercise (P = NS). The fractional catabolic rate was nearly doubled from rest to exercise (P < 0.05 vs rest) and increased to an even greater extent during the early phase of recovery (P < 0.001 vs rest). During the late recovery phase, the value returned to the preexercise value (P = NS vs rest). The values for the absolute catabolic rate (kabs) followed the same trend.

CONCLUSION

VLDL-TAG turnover was increased during exercise and during the early phase of recovery.

Performance and sleepiness during a 24 h wake in constant conditions are affected by diet

This study investigated the effects of high-carbohydrate (HC) and high-fat (HF) diet on cognitive performance, and subjective and objective sleepiness. Seven male participants were kept awake for 24 h in a metabolic ward. Meals were given every 4h and cognitive performance and sleepiness ratings were assessed hourly. The Karolinska Drowsiness Test (KDT, EEG derived) was performed twice after meal. Performance in simple reaction time showed a significant interaction of diet and the post-prandial period, a slower reaction time was observed for the HC-diet 3.5 h after meal intake. Diet did not affect EEG measures but a general post-prandial increase of objective sleepiness was observed 3.5h after meal servings. The HC-diet was significantly associated with an increase of subjective sleepiness. The study demonstrated that the HC-diet caused larger oscillation in performance and increased sleepiness as compared to HF-diet throughout day and night.

The human body may buffer small differences in meal size and timing during a 24-h wake period provided energy balance is maintained

Because approximately 20% of the work force in the industrialized world have irregular working hours, it is pertinent to study the consequences of eating at irregular, especially nighttime hours. We studied the postprandial responses during nocturnal fasting vs. eating throughout a 24-h wake period. Seven healthy males were studied twice in a crossover design. After a 6-d diet adjustment period [high fat diet, 45 energy percent (en%) fat, 40 en% carbohydrates)] with sleep from 2300 to 0700 h, the men were kept awake for 24 h at the metabolic ward and given either 6 isoenergetic meals, i.e., every 4 h (N-eat) or 4 isoenergetic meals from 0800 to 2000 h followed by a nocturnal fast (N-fast), with the same 24-h energy intake. Energy expenditure, substrate utilization, activity, heat release, body temperature and blood variables were measured over 24 h. Energy expenditure and blood glucose, triacylglycerol, insulin and glucagon concentrations were lower and nonesterified fatty acids concentrations were higher during the nocturnal fast than during nocturnal eating (P < 0.05); however, no 24-h differences between the protocols were apparent. Nocturnal fasting slightly altered the secretory patterns of the thyroid hormones and cortisol (P < 0.05). We found no clear indication that it would be more favorable to ingest few larger daytime meals than smaller meals throughout the 24-h period. The body seems to be able to buffer small differences in meal size and timing provided energy balance is maintained.

Endocrine responses to nocturnal eating--possible implications for night work

BACKGROUND

Night work is becoming more common and shift workers display several metabolic disturbances. Aim To study the endocrine responses in relation to time of day during a 24-h period and how dietary macronutrient composition affects these responses.

DESIGN

Seven males (26-43 y and 19.9-26.6 kg. m(-2)) were studied in a crossover design. Isocaloric diets described as high-carbohydrates (HC; 65 energy percent (E%) carbohydrates and 20E% fat) or high-fat (HF; 40E% carbohydrates and 45E% fat) were given. After a 6-day diet adjustment period, the subjects were kept awake for 24 h in a metabolic unit and were served an isocaloric meal (continuation of respective diet) every 4-h. Blood samples were taken throughout the 24-h period.

RESULTS

Insulin and leptin responses to meal intake differed with respect to time of day (p < 0.05). Time of day affected glucagon, thyroid stimulating hormone (TSH), free thyroxin (fT4), total triiodothyronine (tT3), cortisol, chromogranin A (CgA) and pancreatic polypeptide (PP) concentrations (p < 0.05). Meal intake decreased cortisol concentration after meals at 0800, 1200 and 0400 but not at 1600, 2000 and 0000 h. The PP's postprandial increase was greater during 0800-1600 h compared to 2000-0800 h. With the HC meals, lower glucagon and CgA concentrations (p < 0.05), and a tendency for lower tT3 concentrations (p = 0.053) were observed compared to the HF meals.

CONCLUSION

Insulin, PP, TSH, fT4, cortisol and leptin responses to meal intake differed with respect to time of day. The decreased evening/nocturnal responses of cortisol and PP to meal intake indicate that nocturnal eating and night work might have health implications.

Metabolic responses to nocturnal eating in men are affected by sources of dietary energy

Because night work is becoming more prevalent, we studied whether feeding at different times of a 24-h period would elicit different metabolic responses and whether dietary macronutrient composition would affect these responses. Seven men (26-43 y, 19.9-26.6 kg/m(2)) consumed two isocaloric diets, in a crossover design. The diets were a high carbohydrate (HC) diet [65 energy % (E%) carbohydrates, 20E% fat] and a high fat (HF) diet (40E% carbohydrates, 45E% fat). After a 6-d diet-adjustment period, the men were kept awake for 24 h and the food (continuation of respective diet) was provided as six isocaloric meals (i.e., every 4 h). Energy and substrate turnover, heart rate, mean arterial pressure (MAP), blood glucose, triacylglycerol (TAG), nonesterified fatty acid (NEFA) and glycerol were measured throughout the 24-h period. Significantly higher energy expenditure and NEFA concentration, and lower blood glucose and TAG concentrations were observed when the men consumed the HF diet than when they consumed the HC diet. Significant circadian patterns were seen in body and skin temperature (nadir, 0400-0500 h). When the men consumed the HF diet, significant circadian patterns were seen in fat oxidation (nadir, 0800-1200 h; plateau, 1200-0800 h), heat release (nadir, 0800-1200 h; plateau, 1600-0800 h), heart rate (nadir, 0000 h), blood glucose (nadir, 0800-1200 h; peak, 0000-0400 h), NEFA (nadir, 0800-1200 h; peak, 1200-2000 h) and TAG (nadir, 0800-1200 h; peak, 0400-0800 h) concentrations. Energy expenditure, carbohydrate oxidation, MAP and glycerol concentration did not display circadian patterns. Unequal variances eradicated most circadian effects in the HC-diet data. The increased TAG concentration in response to feeding at 0400 h might be involved in the higher TAG concentrations seen in shift workers. Distinct macronutrient/circadian-dependent postprandial responses were seen in most studied variables.

Time of day type of food--relation to mood and hunger during 24 hours of constant conditions

A six-day high-carbohydrate meal (HC; 65 E% (energy percent) carbohydrates, 20 E% fat and 15 E% protein) and a six-day high-fat meal (HF; 40 E% carbohydrates, 45 E% fat and 15 E% protein) were given to seven healthy subjects in a crossover design. On the last day subjects were kept awake for 24 hours in a metabolic laboratory while substrate utilisation and energy expenditure were measured by indirect calorimetry. The subjects were given isocaloric meals every four hours. Results showed that hunger decreased at night (F = 4.2, p < 0.05) and linearly increased after meal intake. Macronutrient composition (fat/carbohydrates) seemed to be of less importance for hunger. Hunger and thirst were found to be strongly associated with gastrointestinal substances, for hunger the strongest being a negative correlation with triacylglycerol (partial correlation = -0.39). It is suggested that it might not be necessary for shift workers to eat full portions at night but that satiation will occur with less food. Possibly lack of adjustment of nocturnal food intake might be one reason why overweight is common in shift work populations.

Inverse relationship between protein intake and plasma free amino acids in healthy men at physical exercise

The effect of a "normal" (n = 8) and "high" (n = 6) protein intake (1 and 2.5 g x kg(-1) x day(-1), respectively) and of exercise on plasma amino acid (AA) concentrations, insulin, and glucagon concentrations was followed throughout a continuous 24-h period in adult male subjects at energy balance after six days on a standardized diet and exercise program. Subjects were fasting from 2100 on day 6 to 1200 on day 7 and then fed 10 identical meals hourly until 2100. Physical exercise was performed (46% maximal oxygen uptake) between 0830 and 1000 (fasting) and in a fed state (1600-1730) on each day. The normal-protein group showed fasting plasma AA concentrations that were higher (P < 0.05) than those for the high-protein group, except for leucine, methionine, and tyrosine. Glutamine, glycine, alanine, taurine, and threonine concentrations were distinctly higher ( approximately 30% or greater) throughout the 24-h period in subjects consuming the normal- vs. the high-protein diets. Exercise appeared to increase, although not profoundly, the plasma concentrations of amino acids except for glutamate, histidine, ornithine, and tryptophan. The profound diet-related differences in plasma AA concentrations are only partially explained by differences in the renal clearance of the amino acids. We speculate on the possible metabolic basis for these findings.