Almost half of U.S. adults will be considered obese by 2030 — with women, African Americans and people in low-income households most vulnerable, according to new projections published Wednesday in the New England Journal of Medicine.

Researchers said those groups in particular are on a rapid course for "severe obesity," which is typically a body mass index of over 35, or about 100 pounds of excess weight.

"That used to be pretty rare," said Zachary Ward, lead author of the new research, as well as a doctoral candidate at Harvard University. "But we're finding that it's quickly becoming the most common BMI category in those subgroups."

The health implications of carrying too much weight have been well documented with links to heart disease, stroke, type 2 diabetes, as well as at least a dozen types of cancer. In January, the American Cancer Society found that obesity-related cancers are rising, including a third of liver cancer deaths linked to obesity.

Obesity is getting worse everywhere in every state.

Ward's team started with BMI data collected from 6.27 million adults. Body mass index is considered a valid indicator of weight health because it takes into account both how much a person weighs and how tall the person is.

The BMI information came from the adults themselves through phone surveys. But because people tend to overestimate their height and underestimate their weight, the findings were likely biased, Ward said. So the researchers brought in another set of data, this time from actual height and weight measurements taken in a doctor's office, and adjusted the body mass indexes from those 6 million adults according to real-life calculations.

Based on the current trends, the team predicted that by 2030, 48.9 percent of U.S. adults will be considered obese, with a BMI of 30 or higher, and 24.2 percent will be in the "severe obesity" category.

"Obesity is getting worse everywhere in every state in terms of the number of people who are developing obesity and the degree or the severity of obesity," Ward said.

While no state is projected to have an obesity prevalence below 35 percent, the problem is expected to be concentrated in parts of the southeastern U.S. and the Midwest with higher levels of poverty.

"In places like Mississippi, Alabama, Oklahoma, we're projecting that they're going to be close to 60 percent obesity prevalence in 2030," Ward told NBC News.

Evidence is growing that shedding even just a few pounds can have dramatic and positive impacts on health. On Monday, researchers reported postmenopausal women can cut their risk for breast cancer if they can sustain a weight loss of at least four pounds.

But losing weight — and keeping it off — is difficult, especially for women who tend to put their families' health ahead of their own, experts said.

"They'll focus on making sure that their children have healthy food," said Marlene Schwartz, director of the Rudd Center for Food Policy and Obesity at the University of Connecticut.

"Their own health is not prioritized," she added.

Racial and ethnic minorities, as well as economically vulnerable populations, face particular barriers as they try to move away from food high in fat, sugar and starch.

"There are big obstacles to making significant changes in the food environment. You're fighting against the economic reality that inexpensive food is often not healthy food," Schwartz said.

"We need to find ways to make it more affordable for people to buy healthy food," she added.

There is evidence that providing healthier food and drink options at lower costs can work to reverse obesity trends. This past summer, a study from the Centers for Disease Control and Prevention found obesity rates among preschoolers enrolled in the federal Women, Infants and Children nutrition aid program dropped to 14 percent in 2016 from 16 percent in 2010.

Some experts attributed the decline in part to changes in the WIC program that switched from high-fat to low-fat milk, and cut the amount of sugar-sweetened juice permitted for the children.

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