By Dorene Internicola

NEW YORK, Jan 6 (Reuters) - For people fighting to get fit in 2014, fitness experts say a New Year's resolution to get in shape can be an important first step and can increase overall success.

Losing weight and getting fit are among the top five resolutions every year although many good intentions run aground by the spring. But the resolution itself carries some power.

"Research suggests that success is higher (among those who make resolutions), than those who make no resolutions at all," said Dr. Barbara Bushman, a clinical exercise specialist with the American College of Sports Medicine.

Bushman, a professor at Missouri State University, said success favors the realistic. About 45 percent of Americans make New Year's resolutions, according to researchers at the University of Scranton. About eight percent achieve their goal.

Jacqueline Ratliff, an exercise physiologist with the American Council on Exercise, borrows an acronym from project management to delineate successful goal-setting.

"With regard to New Year's resolutions, it is important for people to make these goals S.M.A.R.T. (specific, measurable, attainable, relevant, and time-bound)," she explained.

Although the initial motivation might be something intrinsic, like the desire to fit into a smaller size, Ratliff said success is sustained through internal motivation, such as enjoying the feelings associated with working out.

"Think of health and fitness like the stock market," she added. "Your goal in initially investing is not to get rich quick, it is to secure long-term wealth or, in this case, health."

Arizona-based wellness and weight management coach Lauve Metcalfe said: "Many people have difficulty with New Year's resolutions because they have unrealistic expectations."

She said lack of positive support and negative family dynamics can wreak havoc on the best of intentions.

"Putting yourself first is paramount," she added.

(Editing by Patricia Reaney and Stephen Powell)