Obesity rates have increased in most age groups in the United States in recent years, but the biggest rise has been in older adults, according to a new poll.

Over the past five years, the obesity rate among people ages 65 and older has increased by 4 percentage points — from 23.4 percent in 2008 to 27.4 percent in 2014, according to the poll, from Gallup and Healthways.

During that same time period, obesity rates among people ages 45 to 64 increased by 3.5 percentage points (from 29.5 percent to 33 percent), and obesity rates among people ages 30 to 44 increased by 2.3 percentage points (from 27.0 percent to 29.3 percent). Young adults ages 18 to 29 had the smallest increase, at just 0.3 percentage points (from 17.4 percent to 17.7 percent).

Overall, 27.7 percent of American adults were obese in 2014, compared to 25.5 percent in 2008, the poll found. [Lose Weight Smartly: 7 Little-Known Tricks That Shave Pounds]

The results are based on interviews with more than 167,000 U.S. adults in 2014. The participants were asked to state their height and weight, which the researchers used to calculate the participants' body mass index (BMI), a measure of body fatness. People are considered obese if their BMI is 30 or higher.

The increase in obesity rates across nearly all demographic groups underscores the need for health officials, employers and individuals to take actions to decrease these rates, the researchers said.

However, efforts to reduce obesity may need to focus on more than just diet and exercise — the poll also found that being obese was linked with lower overall well-being.

People who were obese scored, on average, between 50.9 and 57.5 out of 100 on a survey of well-being, compared with 64.5 points for normal-weight people. The well-being score was based on people's answers to questions about their feelings toward their community, work and social lives, and their physical health.

"To date, most efforts to curb obesity focus on driving weight loss through diet and exercise, without addressing other aspects of well-being that may contribute to obesity," Janna Lacatell, director of lifestyle solutions at Healthways. "To make a truly measurable impact on reducing obesity rates, interventions should also address other factors known to influence weight management, such as financial and social well-being."

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