Being overweight can also have one hidden cost that many overlook: a negative impact on wages and salary.
Being overweight may affect hiring and promotions, "especially in a tough economy," O'Neill says.
"All things being equal, employers will probably not hire an overweight (or) obese person over others because of the risk of future health care costs," she says.
The impact may be especially negative for women.
"Studies have found that discrimination based on weight in the work place is more prevalent for women than men, especially white women in professional occupations," O'Neill says.
She urges people to begin their weight loss efforts immediately.
"Every small step to improve your health and personal finances can make a difference over time," she says. "Don't wait for the 'perfect' time. Just jump in and start doing a few things every day to improve your health and personal finances."