Obesity is a chronic disease caused by excessive accumulation and abnormal distribution of fat in the body. As early as 2002, the obese population in China was as high as 60 million, and in recent years, the prevalence of obesity among adults in China has been rising, and in 2015, the overweight rate of adults aged 18 and above in China was 30.1% and the obesity rate was 11.9%, up 7.3 and 4.8 percentage points from 2002, especially in middle-aged people. The main danger of obesity is that it can lead to a series of serious health consequences. So, what are the diagnostic criteria for obesity? BMI and waist circumference are the most commonly used measurement indexes, of which BMI is an important index for evaluating whole body fat. BMI is defined as weight divided by height squared (kg/m2). Currently, the World Health Organization defines BMI ≥25 kg/m2 as overweight and ≥30 kg/m2 as obesity. 2011, the Obesity Group of the Endocrinology Branch of the Chinese Medical Association released the diagnostic criteria for adult obesity in China: overweight: BMI 24.0-27.9 kg/m2, obesity: BMI ≥28 kg/m2. In addition, a waist circumference of ≥90 cm for men and ≥85 cm for women is considered visceral obesity. 85 cm, it is considered as visceral obesity. Lulu Chen, Department of Endocrinology, Wuhan Union Hospital Obesity is influenced by genetics, environment and other factors. Many people become fat after entering middle age, which has a great relationship with lifestyle, in addition to individual genes. With the growth of age, people live and work under great pressure after middle age, and have less spare time at their disposal, resulting in insufficient physical activity. On the other hand, influenced by lifestyle, it is easy to form bad eating habits and consume too much energy, thus leading to increased energy intake and reduced consumption, which eventually leads to obesity. In addition, with the increase of age, the body function changes after middle age, the body metabolism slows down, part of the hormone level decreases, the fat is easy to accumulate leading to obesity. Obesity can lead to a series of complications or related diseases, which can affect life expectancy or lead to a reduced quality of life. Obesity is currently considered to be associated with the following chronic diseases: 1. cardiovascular disease: including heart disease and stroke, the risk of hypertension in obese people is 3-4 times that of normal weight people. 2. metabolic diseases, such as diabetes, fatty liver, etc.. Diabetes has become a global epidemic disease, the World Health Organization estimates that in the next 10 years, due to diabetes caused by the death of 50% increase. The risk of diabetes in obese people is 2-3 times that of normal weight people. 3. musculoskeletal diseases: obesity is associated with the development of arthritis. 4. obesity is also associated with reduced cognitive function, depression, sleep apnea syndrome, etc. 5. certain cancers: the development of endometrial cancer, breast cancer, colon cancer has been found to be associated with obesity. Middle-aged people are the high incidence of the above-mentioned diseases, and, unlike obesity in adolescence, middle-aged obese people often combine a variety of metabolic abnormalities, which is more prominent for health hazards. Since obesity has so many hazards, how can we prevent and treat obesity? Obesity prevention mainly relies on lifestyle intervention, in general, is a reasonable diet and exercise. In terms of diet, middle-aged people should eat less high-fat and high-calorie food, and their diet should increase the proportion of vegetables, fruits, whole grains, beans and appropriate control of carbohydrates, and it is best to develop a suitable recipe for themselves under the guidance of doctors or dietitians. In terms of exercise, middle-aged people should adhere to regular exercise, combined with personal work and life situation, to develop a practical exercise plan. And in daily life, try to seize the opportunity to exercise activities, such as walking to and from work when conditions permit, climbing the stairs as far as possible instead of taking the elevator, etc. For patients with joint disorders, swimming is a good choice. The treatment of obesity mainly includes the measures of reducing and maintaining weight and the treatment of accompanying diseases and complications. At present, the treatment of obesity mainly includes medical nutrition treatment, physical activity, cognitive behavior intervention, drug treatment and surgery. 1. the general principle of medical nutrition treatment is to reduce the energy intake in food and beverage; reduce the total food intake; avoid high sugar, high fat and high salt diet; avoid overeating and snacking between meals; avoid eating before bedtime. 2. obese people should keep 30-60min regular and moderate intensity exercise every day. If necessary, the intensity of exercise can be increased for weight control. Physical activities should be arranged according to personal physical ability, age and interest, etc. A certain activity can be the main activity, and then with some other activities to achieve energy consumption. 3. Cognitive-behavioral intervention is also very important for the prevention and treatment of obesity, patients should grasp the scientific views and knowledge about obesity and weight control, establish beliefs, and take behavioral measures to effectively reduce and maintain weight. 4. Weight loss medication, for BMI ≥ 24 kg/m2 with related complications or BMI ≥ 28 kg/m2, after 3-6 months of simple diet and exercise treatment still can not lose 5% of weight, or even still have a tendency to increase weight. For those with BMI ≥ 24 kg/m2 and related complications or BMI ≥ 28 kg/m2 who cannot lose 5% of their body weight after 3-6 months of diet and exercise treatment alone, or even have a tendency to gain weight, weight control drugs can be given. 5. Surgery, obesity and the emergence of metabolic disorder syndrome associated with simple fat excess; abdominal obesity, dyslipidemia; more than 5 consecutive years of stable or stable increase in weight, BMI ≥ 32 kg/m2 can be considered for surgery. About the prevention and treatment of obesity, some patients have some misunderstandings. Some patients think that the treatment of obesity is only for simple weight reduction, but this is not true. Since obesity can lead to many related complications, therefore, the clinical treatment of obesity should focus on the prevention and treatment of complications in addition to weight reduction. For example, middle-aged obese people are often combined with a variety of related diseases, such as hypertension, dyslipidemia, hyperglycemia, fatty liver, etc. Therefore, for middle-aged obese people, it is especially important to carry out prevention and treatment for related complications. In addition, some patients rely too much on weight loss drugs and bariatric surgery, they think that weight loss drugs or bariatric surgery can completely solve the problem of obesity, and ignore the importance of lifestyle intervention in the treatment of obesity. Some patients think they have solved the problem of obesity once and for all after weight loss by medication or surgery, and do not pay attention to lifestyle interventions, resulting in weight rebound soon. As we all know, the occurrence of obesity is closely related to lifestyle, therefore, no matter which way patients take to lose weight, lifestyle interventions should be carried out to the whole of obesity prevention and treatment. In addition, it should be reminded that any way of weight reduction should not be carried out blindly, and it is best to implement it under the guidance of a doctor.