Overweight and obesity are highly prevalent conditions worldwide, despite active research of new interventions over decades. Current interventions include medications or bariatric surgery, but these approaches cannot be used in all patients and require clear indications and a close multidisciplinary management. Therefore most patients and physicians rely on lifestyle interventions, focusing on a balanced diet and physical exercise.

Recent studies have uncovered that energy metabolism is also regulated by circadian rhythms, which depend on spontaneous diurnal oscillations of the central clock, retinal sensing of ambient light, and daily feeding-fasting cycles. The chronotype has an influence on behavioral patterns, where some people describe that they are more alert in the morning or in the evening: The morning or evening chronotypes, respectively. However, in modern societies, many people are exposed to external cues in misalignment with their circadians clocks. The mismatch between the individual chronotype and the social/work life can lead to metabolic disorders.

Time-restricted eating (TRE), i.e. energy intake limited to certain windows of time without restricting calories, is an appealing approach because it proposes to realign the circadian clocks with external cues provided by the timing of food intake, thus leading to better metabolic outcomes.

The investigators speculate that the TRE intervention needs to be personalized to reach efficacy in a broader population. To tailor the TRE intervention to each individual and harmonize their eating patterns in accordance to their chronotype, the investigators plan to test early TRE vs. late TRE vs. active control in overweight and obese individuals with morning chronotype.

Inclusion Criteria:

• Clinical criteria

  • Men and premenopausal women
  • Age 25-50 years
  • BMI 25-34 kg/m2
  • Stable weight (maximum ± 2 kg of usual body weight) over the previous 3 months
  • Stable body fat mass (maximum ± 1 kg of body fat mass) during the run-in phase
  • Eating window ≥ 12 hours during the run-in phase
  • Morning chronotype

• Work-related criteria

  • Daytime work at least 3 days per week over the previous 1 month and planned during the study

• Study-related criteria

  • Able to give informed consent and follow the study procedures for the entire duration
  • Confident use of a smartphone and able to take regular pictures of food/drinks

Exclusion Criteria:

• Clinical criteria

  • Pregnant and breastfeeding women, plans for maternity during the study
  • On a diet, intermittent fasting, in a weight management program over the previous 3 months or planned during the study
  • Eating disorder(s) or prior bariatric surgery
  • Diabetes with hypoglycemic drug(s)
  • Major illness/fever over the previous 1 month
  • Active major cardiovascular, respiratory, liver, gastrointestinal, renal, neurological or endocrine disorders
  • Coagulation disorder, on anticoagulant drug, skin disorder affecting wound healing
  • Active cancer and/or oncologic treatment over the previous 12 months
  • Major sleep disorder (including untreated sleep apnea syndrome), major mental illness
  • Consumption of > 7 standard units of alcohol per week for women and > 14 standard units of alcohol per week for men

• Work and time-related criteria

  • Shift work, such as evening shifts or night shifts, over the previous 1 month or planned during the study
  • Travel/trip to a different time zone (≥ 2-hour time difference) over the previous 1 month or planned during the study

• Study-related criteria and other interventions

  • Enrolled in another interventional clinical trial (medication, medical device) over the previous 1 month and planned during the study
  • Regular medications over the previous 1 month that could affect the study endpoints (e.g. centrally acting, medications affecting gut absorption, transit or weight, hypoglycemic drug, hormonal treatment...)