This is a single-blind, randomized trial. Based on inclusion and exclusion criteria, 253 eligible volunteers, who were 25-60 years old, with overweight/obese and prediabetes are assigned to one of three dietary patterns: healthy Jiangnan, restricted-calorie; Mediterranean, restricted-calorie; or typical Shanghai, restricted-calorie.

The Shanghai Institutes for Biological Sciences of the Chinese Academy of Sciences(CAS) cooperated with Ruijin Hospital to conduct the study which is funded by the CAS. The study' protocol has been approved by the Ethics Committee of Shanghai Institutes for Biological Sciences. The main purpose of this study is to clarify: the efficacy of traditional Jiangnan dietary pattern, Mediterranean dietary pattern and the current Shanghai dietary pattern in improving overweight/obesity, glucose homeostasis, other cardiovascular metabolic risk factors and their main regulatory factors in Chinese.

Nowadays, the prevalence of type 2 diabetes and its related metabolic diseases is rapidly rising in China. Obesity and early pathoglycemia will increase the risk of diabetes and related cardiovascular diseases severely. Therefore, more effective methods and strategies need to be found to reduce body weight, improve pathoglycemia, and control the development of this high-risk group to type 2 diabetes. As the most popular healthy dietary pattern in the world, the role of Mediterranean diet in the prevention of type 2 diabetes remains unclear. In addition, the protective role of Chinese traditional dietary pattern with lots of plant-based foods in the region of Jiangnan has not been clarified through intervention studies. Therefore, it is urgent to explore the feasibility and effectiveness of traditional Jiangnan diet and Mediterranean diet through dietary intervention studies in Chinese.

The effectiveness of healthy dietary patterns can be further enhanced by limiting dietary intake to achieve weight loss. Recently, the Spainish study found that energy-restricted Mediterranean diet + physical activity + behavioral interventions are more conducive to weight loss in overweight/obesity with prediabetes/type 2 diabetes compared with conventional Mediterranean dietary interventions. The 2019 Diabetes Management Standard of American Diabetes Association re-emphasizes the importance of moderate weight loss for delaying the progression of type 2 diabetes, and recommends that a reduction in dietary intake is 500-750 kcal/day to reach 1-2 pounds per week is suitable. At the same time, the American Clinical Endocrine Society and the American Endocrine Society have also updated the 2019 Comprehensive Management Guide for Type 2 Diabetes. The new guidelines point out that all overweight or obese patients with prediabetes or type 2 diabetes should pay attention to weight loss. And weight loss treatment should include specific lifestyle interventions, including calorie-restricted healthy dietary plan, physical activity and behavioral interventions.

Dietary intervention studies in the past mainly relied on dietary education. However, this study now provides a healthy and reasonable dietary model for the Chinese population through lifestyle intervention to clarify the improvement of cardiovascular metabolic risk such as overweight/obesity, glucose homeostasis, and the scientific basis for establishing a healthy dietary model which is suitable for Chinese population.

Inclusion Criteria:

• Age between 25 to 60 years old
• 24.0 ≤ BMI ≤ 40.0 kg/m2
• fasting glucose≥5.6 mmol/L

Exclusion Criteria:

• Diabetes or use of insulin or other hypoglycemic medications
• Pregnancy or lactation
• Trying to change body weight in the way
• Use of antibiotic in the preceding 3 months for 3-serial days
• Obvious changes of medication in the preceding 3 months
• History of drug or alcohol abuse or other substance abuse; (Alcohol abuse is defined as regular alcohol consumption > 40 g/day)
• Any severe liver or renal diseases
• Severe gastrointestinal diseases
• Surgical events preceding 1 year (except appendicitis or hernia surgery)
• Severe cardiovascular or cerebrovascular diseases or phase three hypertension
• Implantation of heart stent
• Cancer or receiving radiotherapy and chemotherapy within 5 years
• Hyperthyroidism or hypothyroidism
• Suffering from hepatitis B, tuberculosis, AIDS and other infectious diseases
• Any mental disorders or current use of antidepressants
• Food contraindications or allergies to foods included in the intervention
• Cognitive disability
• Participated in any other clinical studies within 3 months