Persistently high blood glucose can lead to serious complications.
This could increase the risk of type 2 diabetes and of complications relating to the cardiovascular system, say the researchers.
When a person has obesity, their body is no longer able to process blood sugar in the normal way, but this can be reversed if the person loses weight.
Studies suggest that, following a steady rise over 30 years, rates of obesity in the United States are leveling off. At the moment, obesity affects more than 1 in 3 Americans, or around 35 percent of the population.
Type 2 diabetes often occurs alongside obesity. It is sometimes called a lifestyle disease, because it is frequently linked to a poor diet and lack of exercise, and because a change in lifestyle can reduce the chance of developing it.
Obesity rates improve, but diabetes rates still rising
Researchers from the University of Texas in Galveston and the University of Alabama in Birmingham examined data for over 18,000 adults with obesity. The information was taken from the National Health and Nutrition Examination Survey, and it covered a period of nearly 30 years, from 1988-2014.
- In 2012, 86 million Americans had prediabetes, up from 79 million in 2010
- 1.4 million Americans are diagnosed with diabetes annually
- Diabetes is the 7th leading cause of death in the U.S.
Results showed that from 1988-2014, rates of diabetes rose by up to 19 percent. This, say the authors, explains the general deterioration in blood sugar levels.
The number of obese adults with these three risk factors increased by 37 percent over that time, but another 15 percent did not have these conditions, and that figure remained stable.
People aged from 20-39 years were the least likely in the group to have these three conditions, and this did not change over time.
In those aged 40 years and over, the likelihood of having high blood pressure, high cholesterol, and diabetes decreased over time.
Overall, the average systolic blood pressure and total cholesterol levels fell between 1988 and 1992, and between 2011 and 2014, with the exception of blood pressure in young adults.
Intense intervention needed to combat diabetes and obesity
Co-author Dr. Fangjian Guo, who is an assistant professor of obstetrics and gynecology at the University of Texas, explains that having blood sugar that is persistently high challenges the body's capacity to keep blood sugar within a healthy range.
This leads to a higher risk of developing complications that are related to diabetes.
"The adverse impact of obesity on blood sugar status appears to develop over a longer period of time, and the population is still experiencing progressive worsening of glycemic status."
Dr. Fangjian Guo
Dr. W. Timothy Garvey, a professor of medicine and chair of the Department of Nutrition Sciences at the University of Alabama, who co-authored the report, explains that people with diabetes have a "very high risk" of having a potentially fatal heart attack.
He proposes a more aggressive approach to blood sugar control and weight loss for patients with obesity, because of their high risk of diabetes and heart disease.
Dr. Garvey suggests implementing healthy meal plans and physical activity to achieve these goals.
The team calls for weight control to be a public health priority, to decrease the risk of type 2 diabetes in adults with obesity.