Highlights d 10 h time-restricted eating (TRE) in metabolic syndrome (MetS) promotes weight loss d TRE in MetS reduces waist circumference, percent body fat, and visceral fat d TRE in MetS lowers blood pressure, atherogenic lipids, and glycated hemoglobin d Benefits of TRE are ''add-ons'' to statin and anti-hypertensive medications

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Introduction Career firefighters experience chronic circadian rhythm disruption, increasing their risk of cardiometabolic disease. The recent discovery that eating patterns regulate circadian rhythmicity in metabolic organs has raised the hypothesis that maintaining a consistent daily cycle of eating and fasting can support circadian rhythms and reduce disease risks. Preclinical animal studies and preliminary clinical trials have shown promising effects of time-restricted eating (TRE) to reduce disease risk without compromising physical performance. However, there is a lack of research on TRE in shift workers including firefighters. This study aims to investigate the feasibility and efficacy of 10-hour TRE on health parameters that contribute to cardiometabolic disease risks among career firefighters who work on a 24-hour shift schedule. Methods and analyses The Healthy Heroes Study is a randomised controlled parallel open-label clinical trial with 150 firefighters over 1 year. Firefighters are randomised with a 1:1 ratio to either the control or intervention group. The control group receives Mediterranean diet nutritional counselling (standard of care, ‘SOC’). The intervention group receives the same SOC and a self-selected 10-hour TRE window. After the 2-week baseline, participants enter a 3-month monitored intervention, followed by a 9-month self-guided period with follow-up assessments. The impact of TRE on blood glucose, body weight, body composition, biomarkers (neuroendocrine, inflammatory and metabolic), sleep and mood is evaluated. These assessments occur at baseline, at the end of intervention and at 6, 9 and 12-month follow-ups. Temporal calorie intake is monitored with the smartphone application myCircadianClock throughout the study. Continuous glucose monitors, wrist-worn actigraphy device and questionnaires are used to monitor glucose levels, activity, sleep and light exposure. Ethics and dissemination The study was approved by the Institutional Review Boards of the University of California San Diego and the Salk Institute for Biological Studies. Results will be disseminated through peer-reviewed manuscripts, reports and presentations. Trial registration number NCT03533023; Pre result.

Time-Restricted Eating (TRE) is a consistent 6-12-hour daily eating window without any overt caloric reduction. TRE has been shown in pre-clinical and clinical studies to have widespread benefits including improved cardiometabolic health. Most clinical trials have studied healthy or overweight participants, but the effect of TRE on patients undergoing medical treatment for cardiometabolic disease is unclear. In this single-arm paired-sample pilot study, 19 participants with metabolic syndrome and who had an eating window of 14 hours or more at baseline were put on a 10-hour TRE intervention for 3 months. Despite most participants already taking antihypertensives and statins at baseline, there were significant decreases in blood pressure and LDL cholesterol. There were also significant decreases in HbA1c, waist circumference, and body weight. To better understand the mechanism behind these improvements, here we report the changes in plasma metabolite changes following the 3-month TRE intervention. These findings are important to understand the physiological effects of TRE, especially for individuals to use as a co-treatment.

The suprachiasmatic nucleus (SCN) in the hypothalamus of the vertebrate brain is the central pacemaker regulating circadian rhythmicity throughout the body. The SCN receives photic information through melanopsin-expressing retinal ganglion cells (mRGC) to synchronize the body with environmental light cycles. Determining how these inputs fit into the network of synaptic connections on and between SCN neurons is key to impelling our understanding of the regulation of the circadian clock by light and unraveling the relevant local circuits within the SCN. To map these connections, we used a newly-developed Cre-dependant electron microscopy reporter, APEX2, to label mitochondria of mRGC axons, and serial blockface scanning electron microscopy to resolve the fine structure of mRGC in 3D volumes of the SCN. The maps thus created provide a first draft of the patterns of connectomic organization of SCN in the core and the shell, composed of different neuronal subtypes, and here shown to differ with regard to the patterning of their mRGC input as the shell receives denser mRGCs synaptic inputs compared to the core. This challenges the presently held view that photic information coming directly from the retina is mainly integrated by the core region of the SCN.