Many people are confused about what Body Mass Index (BMI) means as it relates to body fat. Keep in mind that it is just one tool to use when you are looking at your health. Scientists use BMI as a research tool to make objective comparisons as to how fat a person is. A person with a BMI of 25 or above is considered overweight and a BMI over 30 is considered obese.
BMI uses a person's height and body weight to measure a person's fatness. This method has some limitations because it doesn't consider a person's body type (slim, muscular, etc.) For example, a fit person with high muscle mass will tend to have a high BMI which suggests that the person is overfat. This person would actually be fit and healthy with low risk for fat-related diseases. So, even though you might use BMI as a starting point, a person's level of fatness is best measured using a direct method. Two methods used are under-water weighing and skinfold measurements. Under-water weighing is not readily available to most people. Having a skinfold body fat test with calipers done by a fitness professional is convenient and reasonably accurate.
Regular exercise, low body fat and increased muscle mass are all factors that should outweigh any health risks suggested by a higher BMI.