Impact of Nighttime Food Consumption and Feasibility of Fasting during Night Work: A Narrative Review.

Shift work has been associated with an increased risk of developing chronic non-communicable diseases, such as obesity. The reduction in overnight fasting and its physiological consequences seem to affect the metabolic health of shift workers, but little has been discussed regarding the feasibility and implications of maintaining a night-long fast during work. This narrative review aims to discuss the impact of eating behavior on the reduction of overnight fasting in shift workers, as well as possible nutritional strategies involving fasting that have been tested for shift workers, to contribute to the establishment of nutritional guidelines for them. We used various databases and search engines to retrieve relevant articles, reviews, and investigations. Despite the potential benefits of overnight fasting for other groups, few studies have investigated this approach in the context of shift work. Generally, it seems to be a feasible and metabolically beneficial strategy for shift workers. However, it is essential to investigate the potential risks and benefits of reducing the fasting time for shift workers, considering social, hedonic, and stress-related factors. Furthermore, randomized clinical trials are necessary to establish safe and feasible strategies for shift workers to practice different fasting windows.

Is Evening Carbohydrate Intake in Healthy Individuals Associated with Higher Postprandial Glycemia and Insulinemia When Compared to Morning Intake? A Systematic Review and Meta-Analysis of Randomized Crossover Studies.

This systematic review aimed to summarize randomized clinical trials that compared the postprandial glycemic and insulinemic metabolic response after eating isocaloric and standardized carbohydrate meals consumed at two moments: morning versus night, in healthy individuals who were not shift workers. The search strategy consisted of an electronic search using the following electronic databases: MEDLINE (via PubMed), EMBASE (via Elsevier), LILACs (Virtual Health Library - VHL), Cochrane Registers of Clinical Trials (CENTRAL, via Wiley) and gray literature (Opengray.eu). The PICO strategy was used to define the search terms (P: healthy adults, I: nocturnal intake, C: morning intake, O: area under the curve (AUC) of the postprandial glucose and insulin response). This review was reported according to the PRISMA statement. From the 3757 articles found, 412 were duplicates and excluded, totaling 3345 that had their titles and abstracts read. A total of 42 articles met the inclusion criteria and were read in full, and eight studies were included in the systematic review. The certainty of the evidence was assessed using GRADE. The results showed, with moderate quality of evidence, a postprandial response with higher glycemic values in the evening compared to the morning (SMD = 1.30; 95% CI, 1.01 to 1.59; I2 = 0%; p < 0.00001; 8 studies and 116 participants). No differences were found between insulin values at night and in the morning (SMD = 0.19; 95% CI, -0.10 to 0.49; 6 studies and 90 participants). We concluded that the intake of carbohydrates at night leads to higher glycemic, but not insulinemic, postprandial values. Revision Record: PROSPERO number CRD42019137862 available at: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019137862 Key teaching points and nutritional relevanceThis systematic review summarized randomized clinical trials that compared the postprandial glycemic and insulinemic response after eating carbohydrate meals in the morning versus at night.A total of eight studies were included in the systematic review; the results showed a postprandial response with higher glycemic values in the evening compared to the morning.No differences were found between insulin values at night and in the morning;• The intake of carbohydrates at night leads to higher glycemic, but not insulinemic, postprandial values.

Is chronotype associated with dietary intake and weight gain during pregnancy? A prospective and longitudinal study.

OBJECTIVES: The effects of chronotype on dietary intake and weight gain during pregnancy have not been addressed in the literature. The aim of this study was to analyze the effect of chronotype on eating patterns, energy, and macronutrient intake and distribution, as well as weight gain during pregnancy. METHODS: This was a prospective cohort study carried out with 100 pregnant women in the first, second, and third gestational trimesters. Dietary intake was assessed by three 24-h dietary recalls in each trimester, totaling nine recalls. Energy and macronutrient intake and distribution were evaluated at meals throughout the day. Chronotype was derived from midsleep time on free days, and the scores obtained were categorized into tertiles. Recommendations from the Institute of Medicine were used to assess the adequacy of weight gain. Generalized estimating equation models were used to determine the effects of chronotype and gestational trimester on eating patterns, daily energy, macronutrient distribution, and weight gain. RESULTS: Pregnant women with values for midsleep time on free days indicative of eveningness have breakfast later and also have higher energy and carbohydrate intake at dinner than "morning" women. Pregnant "morning" women showed better diet quality in terms of milk and dairy and saturated fat. Also, despite the tendency for all tertiles to gain excess weight during pregnancy, we found that pregnant women with a tendency to eveningness had worse adequacy of gestational weight gain in the third trimester than "morning" women (2.24 ± 0.25 versus 1.22 ± 0.14, P < 0.001). CONCLUSION: Pregnant women with a tendency to eveningness consume breakfast later in the day and exhibit greater consumption of energy and carbohydrates in the evening, as well as a worse standard of gestational weight gain in the third trimester. Our results emphasize the importance of considering chrononutrition variables in prenatal nutritional guidelines to promote maternal and fetal health.

Circadian misalignment measured by social jetlag from early to late pregnancy and its association with nutritional status: a longitudinal study.

A mismatch between circadian and social clocks leads to a circadian misalignment, which has been widely measured by social jetlag (SJL). There are several studies measuring SJL, but it has not been studied in pregnant women. Therefore, this study aimed to identify the occurrence of SJL throughout pregnancy and to verify whether there is an effect of pre-pregnancy body mass index (BMI) on SJL throughout pregnancy. The baseline of the present study was conducted with 205 1st trimester pregnant women of whom 100 were followed in their 2nd and 3rd trimester. SJL was calculated based on the absolute difference between mid-sleep time on workdays versus work-free days. The pre-pregnancy BMI and current BMI (kg/m2) were calculated. Linear regression and Generalised Estimating Equation (GEE) adjusted for confounders were used to determine the association between SJL and the gestational trimesters (time), and anthropometric variables. Most of the pregnant women (54.5%) presented SJL > 1 h in the first gestational trimester. We also found an isolated effect of the gestation trimester on the SJL mean. In this sense, pregnant women had a decrease in SJL from the second to the third trimester (1.33 ± 0.08 versus 1.12 ± 0.07, respectively; p = 0.012). GEE analyzes showed that pregnant women of a normal weight showed a decrease in SJL from the second to the third trimester (1.29 ± 0.11 and 0.93 ± 0.08, respectively, p = 0.032), but this was not found in the other groups of nutritional status (underweight, overweight and obesity). In addition, a positive association between SJL and pre-gestational BMI in the third trimester (ß = 0.200, p = 0.046) was found. SJL is quite prevalent during the gestational period and excessive BMI both before and during pregnancy is associated with an increased risk of having SJL > 1 h in the third and second trimesters, respectively. In addition, pregnant women of normal weight-but not underweight or overweight-had decreased SJL from the second to the third trimester.

Association between chronotype and psychomotor performance of rotating shift workers.

It is known that the chronotype potentially mediates the performance and tolerance to work in shifts and that shift rotation is associated with negative effects on psychomotor performance. This study aimed to evaluate the effect of chronotype on psychomotor performance throughout a complete shift rotation schedule. Thirty males working in clockwise rotating shifts from a mining company were evaluated under a real-life condition over the following shift schedule: 2 days of day work, 2 days of evening work and 2 days of night work. The chronotype was determined using the Munich Chronotype Questionnaire adapted for shift workers and the obtained scores were categorized by tertiles (early-type, intermediate-type and late-type). Work performance was evaluated by Psychomotor Vigilance Test (PVT) daily just before shift starts and after shift ends. Sleep duration was evaluated by actigraphy over the whole shift. No isolated effect of the shift or interaction between shift and chronotype was found in the performance variables evaluated. A significant isolated effect of the chronotype showed that the early-type individuals had higher values of pre- and post-work Mean of Reaction Time (MRT) (308.77 ± 10.03 ms and 306.37 ± 8.53 ms, respectively) than the intermediate-type (257.61 ± 6.63 ms and 252.91 ± 5.97 ms, respectively, p < 0.001) and the late-type (273.35 ± 6.96 ms and 262.88 ± 6.05 ms, respectively, p < 0.001). In addition, late individuals presented a greater number of lapses of attention (5.00 ± 0.92; p < 0.05) than early (1.94 ± 0.50, p < 0.05) and intermediate (1.33 ± 0.30, p < 0.001) ones. We concluded that, compared with intermediates, late-type workers had a greater number of lapses of attention on the shift schedule as a whole, while early-type workers showed the highest pre- and post-work MRT. These findings show that the psychomotor performance of rotating shift workers seems to be influenced by the chronotype, but not by the shift rotation.

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.

Circadian Misalignment Is Negatively Associated with the Anthropometric, Metabolic and Food Intake Outcomes of Bariatric Patients 6 Months After Surgery.

PURPOSE: Circadian misalignment has been associated with an increased risk of overweight and obesity, as well as changes in metabolic parameters. This study evaluated the association between social jet lag (SJL), a measure of circadian misalignment, and anthropometric, metabolic and food intake outcomes 6 months after bariatric surgery. MATERIALS AND METHODS: A total of 122 bariatric patients were included (77% female, aged 33 years (range 28-41); 79.5% underwent Roux-en-Y gastric bypass). Anthropometric, food consumption and SJL were evaluated in the preoperative evaluation and in the third and sixth months after surgery. SJL was calculated based on the absolute difference between the mid-sleep time on weekends and weekdays. Generalised estimating equations and linear regression were performed to evaluate the associations between mean SJL exposure and the outcomes. RESULTS: The interaction between SJL and follow-up time negatively influenced the evolution of weight (p = 0.01), BMI (p = 0.04) and insulin levels (p = 0.01). SJL had an effect on intake of calories (p = 0.001), carbohydrate (p = 0.005) and total (p = 0.007), monounsaturated (p = 0.03) and polyunsaturated fat (p < 0.001). Linear regression showed a negative association between mean SJL exposure over the 6 months and the percentage of weight loss (coefficient = - 0.30, p = 0.006), body weight loss (kg) (coefficient = - 0.17, p = 0.03) and the reduction of BMI (coefficient = - 0.24, p = 0.007). CONCLUSIONS: SJL was negatively associated with anthropometric, metabolic and food consumption outcomes 6 months after bariatric surgery. Future studies with longer follow-up are needed to confirm these findings. TRIAL REGISTRATION: Clinical Trials.gov : NCT03485352.

Effect of consuming a late-night high-protein/moderate-carbohydrate vs. low-protein/high-carbohydrate meal by night workers on their food perceptions later during the day: a randomized crossover study.

It is typical of night workers to consume a large dinner meal before their work shift, even though this practice may increase the risk for metabolic disorders. Night workers usually eat at night to socialize with colleagues as well as to stay alert and to avoid upset stomach during the night shift. However, little is known if and how the composition of the nighttime meal by night shift workers influences their food perceptions and eating behavior later during the day. The aim of this study was to analyze the effect of a high-protein/moderate-carbohydrate (HP/MCHO) meal vs. low-protein/high-carbohydrate (LP/HCHO) meal eaten at night by night-shift workers on their food consumption and perceptions later during the day. Fourteen male night shift workers were followed-up for 7 days for their eating and sleep habits. Then, participants underwent two isocaloric dietary events - one event a HP/MCHO meal containing 45% carbohydrate, 35% protein, and 20% fat and the other event a LP/HCHO meal containing 65% carbohydrate, 15% protein, and 20% fat, with a 6-day washout period between them - at 01:00 h during their night shift. Thereafter throughout the day, participants filled a food register of all the food consumed and perceptions, including hunger before meals, enjoyment of meals, and satiety. Generalized estimating equation analyses were used to examine the effect of both conditions on food consumption and food perceptions. Appetite for salty food snacks was greater after the HP/MCHO condition than after the LP/HCHO condition (p = .041). During the day following consumption of the nighttime HP/MCHO vs. LP/HCHO meal, there was higher percentage of carbohydrate consumption during lunch and a lower percentage of fat consumption during dinner (48.14% vs. 36.98% and 27.34% vs. 40.39%, respectively). These findings suggest the composition in terms of carbohydrates, protein, and fats of the meal consumed for the night shift by night workers may affect later during the day both food consumption and perceptions.

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.

Oxidative stress and fatty acid profile in Wistar rats subjected to acute food restriction and refeeding with high-fat diets.

PURPOSE: To assess oxidative stress and the profile of fatty acids incorporated into the hepatic tissue of animals refed with high-fat (HF) diets after acute food restriction. METHODS: Fifty male Wistar rats were divided into five groups and fasting for 48 hours. One group was sacrificed without refeeding (NR), a control group (C) was refed with the standard AIN-93 diet and the remaining groups with HF diets respectively consisting of hydrogenated vegetable oil (PHVO), trans-free (TF) margarine and trans-free margarine enriched with ω-3 and ω-6 (O). After this period the animals were sacrificed for malondialdehyde (MDA), catalase and hepatic fatty acid determination. RESULTS: The groups refed with HF diets showed elevation of MDA levels compared to the C group (p<0.001 for GVH and p<0.01 for TF and O). Hepatic catalase activity was higher in the TF and O groups compared to group C (p<0.05 for both). The amount of saturated fatty acids was lower in the PHVO and O groups compared to the remaining ones (p<0.001). CONCLUSION: The consumption of high-fat diets after prolonged fasting favors oxidative imbalance in hepatic tissue.

Oxidative stress and fatty acid profile in Wistar rats subjected to acute food restriction and refeeding with high-fat diets

To assess oxidative stress and the profile of fatty acids incorporated into the hepatic tissue of animals refed with high-fat (HF) diets after acute food restriction. METHODS: Fifty male Wistar rats were divided into five groups and fasting for 48 hours. One group was sacrificed without refeeding (NR), a control group (C) was refed with the standard AIN-93 diet and the remaining groups with HF diets respectively consisting of hydrogenated vegetable oil (PHVO), trans-free (TF) margarine and trans-free margarine enriched with ω-3 and ω-6 (O). After this period the animals were sacrificed for malondialdehyde (MDA), catalase and hepatic fatty acid determination. RESULTS: The groups refed with HF diets showed elevation of MDA levels compared to the C group (p<0.001 for GVH and p<0.01 for TF and O). Hepatic catalase activity was higher in the TF and O groups compared to group C (p<0.05 for both). The amount of saturated fatty acids was lower in the PHVO and O groups compared to the remaining ones (p<0.001). CONCLUSION: The consumption of high-fat diets after prolonged fasting favors oxidative imbalance in hepatic tissue.