Obesity increases the risk of other health conditions such as heart disease and stroke.
The researchers also found that around 35 percent of men and 40 percent of women in the U.S. were obese in 2013-2014.
Previous research has shown that obesity rates rose significantly among both men and women between 1980 and 2000. Increases in obesity were recorded among men but not women through 2003-2004. No significant increases were since found for men or women from 2003-2004 to 2011-2012.
Katherine Flegal, of the National Center for Health Statistics, and colleagues set out to examine the prevalence of obesity for 2013-2014. They also aimed to examine overall trends in obesity from 2005 to 2014.
To do so, the researchers looked at data taken from the National Health and Nutrition Examination Survey (NHANES).
NHANES is a long-running nationally representative health survey of the U.S. population. From its most recent period, 2013-2014, the researchers examined data for 2,638 adult men with an average age of 47, and 2,817 women with an average age of 48.
To investigate obesity trends between 2005 and 2012, the researchers also used data from 21,013 participants of the NHANES surveys during this time.
Past results from the NHANES surveys have shown that obesity rates vary by sex, age, race, socioeconomic status, and smoking habits. As a result, the researchers adjusted their findings for these factors.
Class 3 obesity also increased among women but not men
The findings of the study, published in JAMA, reveal that the age-adjusted rates of obesity in 2013-2014 were 35 percent in men and 40.4 percent in women.
The rates of class 3 obesity, where a person has a body mass index (BMI) of 40 or higher, were 5.5 percent for men and 9.9 percent for women.
For men, obesity was significantly lower among those who smoked, compared with those who had never smoked. This was not the case among women; instead, those with a high level of education were significantly less likely to be obese.
From 2005 to 2014, the researchers found significant increasing trends for both overall obesity and class 3 obesity among women. No significant trends, however, were observed for men.
The researchers measured obesity using weight and height measurements recorded in the surveys. The authors acknowledge that this was a limitation of their study, as they did not take into account body fatness.
Obesity increases the risk of many other health conditions. These include:
- High blood pressure (hypertension)
- Type 2 diabetes
- Heart disease
- Some forms of cancer.
In addition to these, the Centers for Disease Control and Prevention (CDC) state that obesity raises the risk of all causes of death. As a result, treating and preventing obesity is a high priority.
In an editorial accompanying the study in JAMA, Dr. Jody Zylke and Dr. Howard Bauchner write that the development of new drugs and procedures will not solve the problem:
"The emphasis has to be on prevention, despite evidence that school- and community-based prevention programs and education campaigns by local governments and professional societies have not been highly successful."
As a solution, they suggest that prevention could be led by "collaboration with the food and restaurant industries that are in part responsible for putting food on dinner tables."
Part of being able to prevent obesity is understanding why it happens in the first place. Unfortunately, Flegal and her colleagues state that data are lacking to show the causes of obesity trends.
"Other studies are needed to determine the reasons for these trends," the authors conclude.