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Up to 20% of the population in industrialised countries are employed as shift workers. Shift work is an independent risk factor for metabolic diseases, such as type-2 diabetes, cardiovascular disease (CVD) and obesity. This may be associated with shift workers’ typical habit of eating during the night, as it forces the body to process nutrients when the body is expecting a period of fast. This study aimed to examine whether redistributing meal times, to create a defined overnight fast period, can improve CVD risk factors in night shift workers.
Eligible participants were permanent or rotating night shift workers who habitually ate on night shift between 1am to 6am and had abdominal obesity as assessed by waist circumference, but were otherwise healthy. This randomised crossover trial comprised a four-week control period and a four-week intervention period separated by a minimum two-week washout period. During the intervention period, participants were advised to rearrange meal and snack times to create a five hour nightly fast between 1am and 6am. Up to four random 24-hour food recalls per participant were performed during both periods of the study, to check compliance and to assess energy intake. All recall periods included a night shift. Participants attended the research facility at the end of each period to be weighed (seca, gmbh & co. kg, Hamburg, Germany). Work schedule and meals were standardised 24 hours prior to attending the research facility. Data were analysed using paired t-test and reported as mean (SD).
Participants (n = 19) were aged 41(10) years. Daily energy intake was not markedly different between the two study periods, intake was 10633 (3591) kJ/ day in the intervention period vs. 10919 (4276) kJ/ day in the control period (n = 60 recalls in each period, p = 0.670). Body weight was significantly lower at the end of the intervention period compared with at the end of the control period (86.2 (17) vs. 87.1 (18) kg, p = 0.001). Similarly, BMI was lower at the end of the intervention period compared with end of control period (30.7 (6) vs. 31.1 (6) kg/m2, p = 0.001).
Increasing evidence indicates that working night shifts potentiates weight gain. We show that advising shift workers to avoid eating during 1am and 6am for a four-week period had a positive impact on body weight. Manipulating meal and snack times for shift workers may be a simple strategy to assist in weight management.
Randomised controlled trials comparing low- v. high-fat diets on cardiometabolic risk factors in people with overweight or obesity have shown inconsistent results, which may be due to the mixed metabolic status of people with excess adiposity. The role of dietary fat manipulation in modifying cardiometabolic indicators in people with overweight or obese without metabolic disturbance is unclear. Thus, meta-analysis was conducted to compare low- v. high-fat diets on cardiometabolic indicators in people who are overweight or obese without metabolic disturbance in the present study. Databases were searched until October 2016. The pooled effects of outcomes with heterogeneity were calculated with a random-effects model, heterogeneities were analysed by subgroup and meta-regression. As a result, twenty studies with 2106 participants were included in the meta-analysis. Total cholesterol and LDL-cholesterol levels were lower following low-fat diets compared with high-fat diets: weighted mean difference (WMD) was −7·05 mg/dl (−0·18 mmol/l; 95 % CI −11·30, −2·80; P=0·001) and −4·41 mg/dl (−0·11 mmol/l; 95 % CI −7·81, −1·00; P=0·011), respectively. Conversely, significant higher level of TAG (WMD: 11·68 mg/dl (0·13 mmol/l), 95 % CI 5·90, 17·45; P<0·001) and lower level of HDL-cholesterol (WMD: −2·57 mg/dl (−0·07 mmol/l); 95 % CI −3·85, −1·28; P<0·001) were found following low-fat diets compared with high-fat diets. In conclusion, dietary fat manipulation has a significant influence on blood lipid levels in people with overweight or obesity without metabolic disturbances.
This meta-analysis of randomised controlled trials assessed the effect of Ca on body weight and body composition through supplementation or increasing dairy food intake. Forty-one studies met the inclusion criteria (including fifty-one trial arms; thirty-one with dairy foods (n 2091), twenty with Ca supplements (n 2711). Ca intake was approximately 900 mg/d higher in the supplement groups compared with control. In the dairy group, Ca intake was approximately 1300 mg/d. Ca supplementation did not significantly affect body weight (mean change ( − 0·17, 95 % CI − 0·70, 0·37) kg) or body fat (mean change ( − 0·19, 95 % CI − 0·51, 0·13) kg) compared to control. Similarly, increased dairy food intake did not affect body weight ( − 0·06, 95 % CI − 0·54, 0·43) kg or body fat change ( − 0·36, 95 % CI − 0·80, 0·09) kg compared to control. Sub-analyses revealed that dairy supplementation resulted in no change in body weight (nineteen studies, n 1010) ( − 0·32, 95 % CI − 0·93, 0·30 kg, P= 0·31), but a greater reduction in body fat (thirteen studies, n 564) ( − 0·96, 95 % CI − 1·46, − 0·46 kg, P < 0·001) in the presence of energy restriction over a mean of 4 months compared to control. Increasing dietary Ca intake by 900 mg/d as supplements or increasing dairy intake to approximately 3 servings daily (approximately 1300 mg of Ca/d) is not an effective weight reduction strategy in adults. There is, however, an indication that approximately 3 servings of dairy may facilitate fat loss on weight reduction diets in the short term.
Identifying dietary modifications that potentiate the blood pressure (BP)-lowering effects of antihypertensive medications and that are practical for free-living people may assist in achieving BP reduction goals. We assessed whether two dietary patterns were effective in lowering BP in persons on antihypertensive therapy and in those not on therapy. Ninety-four participants (38/56 females/males), aged 55·6 (sd 9·9) years, consumed two 4-week dietary regimens in random order (Dietary Approaches to Stop Hypertension (DASH)-type diet and low-Na high-K (LNAHK) diet) with a control diet before each phase. Seated home BP was measured daily for the last 2 weeks in each phase. Participants were grouped based on antihypertensive drug therapy. The LNAHK diet produced a greater fall in systolic BP (SBP) in those on antihypertensive therapy ( − 6·2 (sd 6·0) mmHg) than in those not on antihypertensive therapy ( − 2·8 (sd 4·0) mmHg) (P = 0·036), and this was greatest for those on renin–angiotensin system (RAS) blocker therapy ( − 9·5 (sd 6·4) mmHg) (interaction P = 0·007). The fall in SBP on the DASH-type diet, in those on therapy (overall − 1·1 (sd 6·2) mmHg; renin–angiotensin blocker therapy − 4·2 (sd 4·7) mmHg), was not as marked as that observed on the LNAHK diet. Dietary modifications are an important part of all hypertension management regimens, and a low-Na and high-K diet enhances the BP-lowering effect of antihypertensive medications, particularly those targeting the RAS.
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