Weight regain after weight loss is a major problem in the treatment of obesity. Two novel types of intermittent fasting recently have received more attention: the 5:2 diet and time-restricted eating (TRE). TRE requires individuals to eat in a specified number of hours per day (typically 4 to 10 hours) without energy intake restriction. The 5:2 diet involves 5 feast days and 2 fast days per week; participants eat ad libitum without restriction on feast days while 25% of energy needs (approximately 500-800 kcal per day) are consumed on fast day. This randomized controlled trial aimed to evaluate the effect of TRE and the 5:2 diet on weight loss maintenance and cardiometabolic risk factors after a low-calorie diet in obese adults over 12 months compared to usual health care.

Weight regain after weight loss is a major problem in the treatment of persons with obesity. Two novel types of intermittent fasting recently have received more attention: the 5:2 diet and time-restricted eating (TRE). TRE requires individuals to eat in a specified number of hours per day (typically 4 to 10 hours) without energy intake restriction. The 5:2 diet involves 5 feast days and 2 fast days per week; participants eat ad libitum without restriction on feast days while 25% of energy needs (approximately 500-800 kcal per day) are consumed on fast day. Preliminary evidence suggests that both TRE and the 5:2 diet have beneficial effects on weight loss and cardioprotection in humans. Whether TRE or the 5:2 diet is an effective approach for weight-loss maintenance remains unknown. This randomized controlled trial aimed to evaluate the effect of TRE and the 5:2 diet on weight loss maintenance and cardiometabolic risk factors after a low-calorie diet in obese adults over 12 months compared to usual health care. All participants who have achieved greater than 5% of weight loss after a 8-week low-calorie-diet induced weight loss phase, will be assigned to one of the three study groups (TRE, the 5:2 diet and control groups) in a 1:1:1 ratio. Participants in the TRE group will be instructed to eat during a window of 8 h/d (8 am to 4 pm) over 12 months. Participants in the 5:2 diet group will be instructed to consume 500-600 kcal/d on fast days and eat ad libitum on feast days. Participants in the control group were instructed to receive usual health care.

Inclusion Criteria:

• 1.Man or women aged 18-75 years;
• 2.Body mass index (BMI)of 28.0 to 45.0 kg/m2;

Exclusion Criteria:

• 1. History of HIV, hepatitis B or C (self-report) or active pulmonary tuberculosis;
• 2. Diagnosis of type 1 and type 2 diabetes;
• 3. History of malignant tumors;
• 4. Serious liver dysfunction or chronic kidney disease (AST or ALT > 3 times the upper limit of normal, or eGFR<30 ml/min/1.73 m2);
• 5. History of serious cardiovascular or cerebrovascular disease (angina, myocardial infarction or stroke) in the past 6 months;
• 6. History of severe gastrointestinal diseases or gastrointestinal surgery in the past 12 months;
• 7. History of Cushing's syndrome, hypothyroidism, acromegaly, hypothalamic obesity;
• 8. Being a smoker or having been a smoker in the 3 months prior to their screening visit;
• 9. Taking medications affecting weight or energy intake/energy expenditure in the last 6 months, including weight loss medications, antipsychotic drugs or other medications as determined by the study physician;
• 10. Currently participating in weight loss programs or weight change in the past 3 months (> 5% current body weight) ;
• 11. Women who are pregnant or plan to become pregnant;
• 12. Patients who cannot be followed for 24 months (due to a health situation or migration);
• 13. Patients who are unwilling or unable to give informed consent.