The global obesity epidemic is well established, and is an important public health issue. The previous researches had applied the clues that obesity is a kind of systemic disease. The investigators hypothesized that a serious alteration of the body systems will occur after bariatric surgery, which may shed light on the mechanisms of obesity. Thus, the research aims to combine the imaging and surgery to investigate the alterations of the body that induced by obese and alterations after surgery.

In 2016, the prevalence of obesity has already reached 13% of obesity and about 40% overweight worldwide. There is no doubt that obesity is linked to a broad spectrum of diseases，such as cardiovascular diseases, fatty liver diseases, polycystic ovarian syndrome and even central nervous systems disorders. For instance, in a review, author indicated the insulin resistance of T2DM occurs primarily in the muscles of lean individuals before they become obese. The central nervous system, especially the hypothalamus, has always considered to be the regulation center of food intake and hormonal regulation of energy homeostasis. In turn, obesity may worsen the regularity function of nervous system in several pathway. Based on the previous findings, the investigators hypothesized that a serious alterations of the body systems will occur after bariatric surgery, which may shed light on the mechanisms of obesity. The investigators plan to integrate the MR imaging, biological and epidemiological data thoroughly to investigate the alterations of the body that induced by obese and also followup the alterations that after surgery.

Inclusion Criteria for obesity group:

Meeting the obesity criteria (BMI > 28); 2) Meeting the indications for bariatric surgery, planning to undergo surgery for the first time; 3) Age between 18-65 years old, no gender restrictions; 4) Right-handed, of Han ethnicity; 5) Informed consent to the study, willing to cooperate with the research, and able to sign an informed consent form.

Inclusion Criteria for the Control Group:

1. Healthy volunteers with a BMI between 18.5-23.9;
2. Age between 18-65 years old, no gender restrictions;
3. Right-handed, of Han ethnicity;
4. Informed consent to the study, willing to cooperate with the research, and able to sign an informed consent form.

Exclusion Criteria for obesity group:

1. Secondary obesity caused by other organic diseases or medication (such as hormone use, etc.);
2. Unable to undergo surgery as planned;
3. Pregnant or breastfeeding;
4. Low cognitive ability and incapable of cooperating with the study;
5. Eating disorders;
6. Alcohol or drug dependence;
7. Meeting the criteria for organic mental disorders, severe mental disorders (schizophrenia, etc.), or other serious mental illnesses requiring clinical intervention;
8. Contraindications for MR scanning (pacemakers, cochlear implants, metal objects in the body, claustrophobia, weight exceeding the machine's load limit, etc.);
9. History of neurological organic diseases (brain tumors, epilepsy, cerebrovascular accidents, severe head trauma, etc.);
10. History of congenital heart disease (myocardial infarction, severe arrhythmias, heart failure, cardiomyopathy, rheumatic heart disease, congenital heart disease, etc.);
11. Severe liver, kidney, lung, digestive dysfunction, endocrine, and blood system diseases;
12. Active infections within the last two weeks (fever, upper respiratory infection, acute gastroenteritis, etc.);
13. Use of drugs affecting the nervous system or psychotropic drugs within the last six months.

Exclusion Criteria for the Control Group:

The same criteria as points 3) to 13) above.

Aged between 18 and 65, regardless of gender. Initially diagnosed as obesity (BMI>28) and plan to undergo bariatric surgery.