Areduction of body weight is the lowest level of body weight loss that can significantly improve health by decreasing blood lipids, blood pressure, and factors related to the onset of type 2 diabetes.

5-10%.

Explanation:

The maintenance of the weight in human beings is important for the individual health. Humans can be classified into three categories depending upon the body mass index - under weight, over weight and normal weight.

The level of cholesterol, proteins and lipids contribute to the weight of an individual.  The over weight individual must reduce their body weight upto 5-10% because this reduction in weight improves their health status and reduce the chances of heart disease.

Thus, the answer is 5-10%.