But in fact, obesity researchers say, no one has any idea how many people can lose weight and keep it off.

Another concern, obesity researchers say, is possible long-term effects of taking the drug for life.

In fact, obesity researchers say, it takes only a modest weight loss - 5 to 10 percent - to improve health.

The calipers quickly became a tool of the trade for obesity researchers.

See also news coverage and reactions from other obesity researchers.

The obesity researchers say they are not trying to be contrarians.

But obesity researchers say the work, which began just two years ago, is encouraging.

Other obesity researchers say Colorado's history makes it the perfect proving ground.

Not everyone is able to do so, obesity researchers say.

Yet other treatments, short of surgery, are not effective for very long, obesity researchers say.