THURSDAY, Aug. 25 (HealthDay News) -- The number of obese people in the United States will increase from 99 million in 2008 to 164 million by 2030, and the number of obese people in the United Kingdom will increase from 15 million to 26 million, a new study predicts.

Obesity-related diseases and health care costs will soar as a result, according to the report published Aug. 26 in The Lancet.

Already, the U.S. and U.K. obesity rates are the highest among the 34 member nations of the Organization for Economic Development and Cooperation (OECD), the study said.

The U.S. obesity rate will rise from 32 percent to about 50 percent for men, and from 35 percent to between 45 percent and 52 percent for women. The U.K. obesity rate will rise from 26 percent to between 41 percent and 48 percent for men, and from 26 percent to between 35 percent and 43 percent for women.

The report, based on analyses of U.S. data from 1988 to 2008 and U.K. data from 1993 to 2008, is the second article in the journal's obesity series.

In the United States, the cost of treating obesity-related diseases, such as diabetes, heart disease and stroke, would increase $66 billion per year by 2030, and represent a 2.6 percent increase in overall health spending.

Spending on obesity problems alone will increase 13 percent to 16 percent per year if U.S. trends continue. About 4 percent of that increase is attributable to an aging population, the study said.

In the U.K., the increase would be £2 billion per year ($3.2 billion), with overall health-care spending rising 2 percent. Spending specifically on obesity disorders will jump 25 percent per year over the next 20 years, with 10 percent of that increase due to population aging, the researchers said.

In the United States, the increasing rates of obesity would mean 7.8 million extra cases of diabetes, 6.8 million extra cases of coronary heart disease and stroke, and 539,000 extra cancer cases by 2030. The U.K. would see 668,000 extra cases of diabetes, 461,000 extra cases of coronary heart disease and 130,000 extra cases of cancer.

Losing just a little weight could offset those increases. The report noted that a 1 percent population-wide decrease in body-mass index (just 1.9 pounds for an average 198-pound adult) would prevent more than 2 million cases of diabetes, roughly 1.5 million cases of heart disease and stroke, and 73,000 to 127,000 cancer cases in the United States.

That same amount of weight loss in the U.K. would cut between 179,000 and 202,000 diabetes cases, 120,000 cases of heart disease and stroke, and 32,000 cancer cases.

Obesity prevalence varied by gender and ethnicity, the study said. In the United States, about one-quarter of all men were obese in 2008 regardless of their race, while 46 percent of black women, one-third of Hispanic women, and 30 percent of white women were obese. In the U.K., 19 percent of white men, 17 percent of black men, and 11 percent of Asian men are obese, along with one-third of black women, 20 percent of white women, and 16 percent of Asian women.

More information

The U.S. National Heart, Lung, and Blood Institute has more about overweight and obesity.