Overweight and obesity happen when the body accumulates too much fat, whether throughout the body, in specific areas, or in organs as ectopic fat, which increases the risk of various health problems.Second, historical links between higher BMI and severe health complications have changed due to improvements in medical care.Measurements such as Body Mass Index (BMI), calculated by dividing weight in kilograms by height in meters squared, and waist circumference are simpler to use and still offer important insights into health risk, even if they are less precise than advanced imaging techniques.This improvement is largely due to better emergency care, wider public use of CPR and defibrillators, advances in intensive care, smoking cessation, and increased use of medications such as aspirin, statins, PCSK9 inhibitors, and blood pressure treatments.While highly accurate methods like underwater weighing, DEXA scans, CT scans, and MRI provide precise body fat measurements, they are not practical in everyday clinical practice.For instance, the risk of type 2 diabetes and early death can rise at BMI levels well below 30 kg/m2, which is commonly used to define obesity in some populations.Overall, current data on overweight and obesity should consider not only illness and death rates but also healthcare use, costs, medications, and the number of treatment procedures performed.A practical system for classifying obesity should be based on measurements that are easy to obtain, reliable for predicting health risks, and useful for guiding treatment decisions.For example, deaths from atherosclerotic cardiovascular disease have declined in the United States even as obesity rates have risen.This perspective allows healthcare providers to focus on both preventing and treating conditions linked to excess weight.Understanding these factors provides a clearer picture of the impact of excess weight on health and helps guide effective prevention and treatment strategies.First, BMI cut-offs are helpful for identifying increasing risk, but the relationship between body fat and health problems is continuous rather than absolute.Early intervention at these lower levels can be more effective in preventing further weight gain and improving overall health.Unlike some chronic diseases, obesity does not require that a related complication has already developed; it is enough that the risk is higher.It is also important to note that the amount of body fat considered excessive can vary between individuals and populations, meaning that the same weight or fat distribution can carry different health risks for different people.There are a few points to keep in mind regarding the thresholds used to define overweight and obesity.In some cases, this has even led researchers to suggest that being slightly overweight may have protective effects for heart health.