Effects of a chronotype-adapted diet on weight loss, cardiometabolic health, and gut microbiota: study protocol for a randomized controlled trial.

BACKGROUND: Obesity and its associated health complications have become a global public health concern, necessitating innovative approaches to weight management. One emerging area of research focuses on the influence of chronotype, an individual's preferred timing for daily activities, on eating habits, weight regulation, and metabolic health. Recent observational studies suggest that the misalignment between an individual's chronotype and external cues, such as meal timing, may contribute to metabolic dysregulation and obesity, but evidence from intervention studies is still limited. This study protocol describes a randomized controlled trial designed to explore the effects of a chronotype-adapted diet, compared with a diet with a conventional calorie distribution, on weight loss, cardiometabolic health, and gut microbiota composition. METHODS: A total of 150 overweight/obese adults will be recruited for this 4-month parallel-group, randomized, two-arm, open-label, superiority trial with 1:1 allocation ratio. Participants will be randomly assigned to either the intervention group or the control group. The intervention group will receive a low-calorie chronotype-adapted diet with a calorie distribution adapted to the individual chronotype (morning or evening), optimizing meal timing according to their peak metabolic periods. The control group will follow a standardized low-calorie healthy eating plan without considering chronotype. Both diets will have equivalent daily calorie content, adjusted according to gender and starting weight. Anthropometric measurements, body composition, blood, and fecal samples will be obtained from each participant at the beginning and the end of the study. The primary outcome is weight change from baseline. Secondary outcomes are changes from baseline in body mass index (BMI), fat mass, lipid and glycemic profile, fecal microbiota profile, and short-chain fatty acids (SCFAs). DISCUSSION: The results of this randomized controlled trial have the potential to advance our understanding of the complex interactions between chronotype, diet, body weight, and health outcomes. By providing evidence for personalized dietary interventions based on individuals' circadian preferences, this research could offer insights into personalized nutrition strategies. Such knowledge could guide the development of innovative dietary interventions to optimize the prevention and management of overweight and obesity, while also improving the risk profile of these individuals. TRIAL REGISTRATION: ClinicalTrials.gov NCT05941871. Registered on 18 May 2023.

Morning chronotype is associated with higher adherence to the Mediterranean diet in a sample of Italian adults.

BACKGROUND AND AIMS: A growing body of evidence has associated subjects with an evening chronotype with worse eating behaviours and poorer diet quality. However, only few studies have investigated the relationship between chronotype and Mediterranean diet (MD). The aim of this study was to better understand the chronotype influence on dietary habits and MD adherence in a large sample of Italian adults. METHODS AND RESULTS: A total of 1247 participants (66.7% women) with a mean age of 36.1 ± 14.6 years were included in the analysis. Chronotype was classified as morning in 35.6% of subjects, intermediate in 56.7%, and evening in 7.1%. Regarding meal frequency, evening subjects showed a significantly (p < 0.05) greater tendency to skip breakfast (20.5%) than morning (6.9%) and intermediate (12%) subjects. Similarly, evening subjects were found to skip mid-morning snack more often than morning subjects (59.1% vs. 47.1%; p = 0.04), and lunch more often than intermediate subjects (8% vs. 2.8%; p = 0.01). In addition, all meals were eaten by evening subjects at a significantly delayed time, except for lunch. As to MD adherence a significant (p < 0.001) higher adherence in morning subjects (10.1 ± 2.2) compared to intermediate (9.5 ± 2.1) and evening (9.5 ± 2.2) subjects was observed. At a logistic regression analysis adjusted for possible confounding factors, morning subjects showed an increased probability (OR 1.54, 95%CI 1.19-1.99; p < 0.001) of being in the highest MD adherence tertile. CONCLUSION: Chronotype was associated with MD adherence. In particular, morning subjects showed higher MD adherence than intermediate and evening subjects.