Scientists in the United States have found that being very overweight, also known as obesity, can leave a long-lasting memory in the body’s immune system. They discovered that even after people lose weight, the immune system may still remember the time when the person was obese. This can help explain why some people continue to have health problems, such as heart disease or diabetes, after losing weight.

The main reason for this is that obesity causes inflammation, which is the body’s way of reacting to injury or illness. Inflammation can change certain immune cells. These changes do not affect the DNA directly but can influence how the DNA works. The scientists found that these changes can remain even after a person becomes thinner.

Because of this immune ‘memory’, some health risks might not go away quickly after losing weight. Scientists say that people who have lost a lot of weight may still need medical check-ups. This research may help doctors find better ways to treat health problems linked to obesity in the future.