This study aimed to explore the effects of quantity and quality of dietary carbohydrate intakes on glucose and lipid levels and metabolism, as well as gut microbiota by a randomized crossover controlled intervention trial.

Inclusion Criteria:

• Male and female aged 18 - 65 years;
• BMI 20 - 35 kg/m2;
• Consent to be randomly assigned to an intervention or control group;
• Willingness to eat the food and beverages provided in the study;
• Patients with or at high risk of metabolic syndrome, and the diagnostic criteria of metabolic syndrome were based on the Chinese Guidelines for the Prevention and Treatment of diabetes (2024 edition).

Exclusion Criteria:

• Use of medications that affect blood glucose metabolism;
• Familial hyperlipidemia, or use of drugs that affect lipid metabolism;
• Long-term or current use of nonsteroidal anti-inflammatory drugs, antibiotics, antihistamines, or immunomodulatory drugs, and unable to stop taking these drugs within 72 h before the start of the study;
• Use of hormonal medications such as anticoagulants, anabolic steroids, and hydrocortisone;
• Have a history of serious illness, or are in the acute stage of cardiovascular, renal, thyroid, gastrointestinal, hepatobiliary, immunologic, respiratory, neurological, musculoskeletal, psychiatric, infectious, and malignant diseases, and are receiving treatment or use of related drugs;
• Self-reported weight gain or loss of more than 7 kg in the 6 months before enrollment;
• Vegetarian;
• Have food allergies or other problems that may affect food intake;
• Unable to consume only the food and beverages provided in the study;
• Drink alcohol more than 2 times per day, more than 14 times per week, and unwillingness to stop drinking during the study;
• Participate in a weight-loss program;
• Unwillingness to maintain weight throughout the study;
• Females who have given birth within the past year, are pregnant or plan to become pregnant within 6 months, are breastfeeding;
• Intend to participate in other dietary intervention studies and drug use studies in the next 4 months;
• Poor venous blood access;
• Any other that the physician assessed as unsuitable for the trial conditions.