With commentary by Frank Hu, MD, PhD, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health.
Diabetes is on the decline in the U.S., after many years of steady increases, according to a new report issued Tuesday by the U.S. Centers for Disease Control and Prevention (CDC). From 2009 to 2014, the number of new cases declined significantly, from 1.7 million to about 1.4 million, according to the latest statistics. This new decline follows decades of increases in diabetes among U.S. adults, driven by the obesity epidemic and a lack of physical activity. In 1980, 493,000 adult in the U.S. had diabetes, according to the CDC. By 2014, that number had grown to 1.4 million.
"It's encouraging news," says Frank Hu, MD, PhD, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health, who reviewed the report. "The prevalence of diabetes has been increasing steadily in the past two decades," Dr. Hu says. "In the past few years, the prevalence has plateaued. This year, the 2014 data show there is actually a substantial decline in the number of people diagnosed with diabetes. It looks like this trend is pretty robust and not artificial due to statistical variability."
However, he adds, "It's too early to celebrate." That is because ''the number of people with diabetes is still unacceptably high in the U.S. One of 10 American adults has diabetes. In total, we have 24 million diagnosed with diabetes and another 5 million undiagnosed."
Most people, about 95%, have type 2 diabetes. The body cannot make enough insulin to control blood sugar or does not use it efficiently enough. In type 1, the body cannot make insulin.
"The single most important risk factor with type 2 diabetes is obesity," Dr. Hu says. "When people gain weight and become overweight or obese, their risk of diabetes will go up dramatically." Having diabetes, in turn, raises the risk of other health problems, such as heart disease and heart attack.
"Besides body weight, certainly diet has a very important role in the development of diabetes," Hu says. "The quality of the diet not only affects body weight, but affects diabetes risk."
Progress has not been even in the population, the CDC report suggests. For instance, among Hispanics, diabetes cases rose from 1997 through 2009 and did not show any consistent change after 2009. Among blacks, there was no significant change from 1997 through 2014. Among whites, after an increase in new cases from 1997 to 2008, the number of new cases dropped from 2008 though 2014. Education played a role. The decline was greater in those with high school education or more, the report also found.
Dr. Hu suspects that dietary improvements are one reason for the decline in diabetes. He says fewer people are drinking sugary beverages, as his research and that of others has found ill effects on health from the drinks, including weight gain. In the last decade, Dr. Hu says, consumption of sugary beverages has declined about 25% in the U.S.
Another factor is an increase in physical activity, he says. As people become more active, they can reduce their risk of getting diabetes.
"Maintaining a healthy body weight is the single most important way to avoid diabetes," Dr. Hu says. Diet is important, too. He prescribes avoiding sugary beverages and refined carbohydrates, increasing intake of fruits, vegetables, and whole grains and limiting red and processed meats.
He isn't suggesting people need to be super-slim to avoid diabetes. "We aren't talking about everyone getting to a 22 or 23 BMI, or body mass index." A 5'8" person who weighs 150 has a BMI of 22.8. Keeping BMI below 25, considered a healthy level, is acceptable to reduce risk, he says. A 5'8" person who weighs 164 has a BMI of 24.9.
Physical activity, getting in about a half hour five days a week, can reduce diabetes risk, Dr. Hu says. He also advises reducing screen time. When people watch too much TV, for instance, they tend to eat more junk food. So reducing sedentary screen time is also important, he says.