Each day before breakfast, the men and women used a bath scale to weigh themselves and measure body fat, then used the breathalyzer.
Those in the first two groups did not lose substantial amounts of weight -- their breath acetone levels were constant. The researchers suggested that the exercise-only group members, allowed to set their own pace, weren't working hard enough.
Those in the third group who followed instructions lost substantial amounts of fat and their breath acetone levels rose.
The researchers speculate that the device might also be used in the prevention and treatment of diabetes. When diabetes is out of control, acetone breath levels rise.
Hiyama could not say what the device might cost or how soon it could be on the market.
"I think it's an interesting device," said Larry Birnbaum, a professor and chair of exercise physiology at the College of St. Scholastica, in Duluth, Minn., who reviewed the findings and has researched fat burning. He pointed out some limitations, including the small study size of 17 people.
One strength of the study, he said, is that the device results were compared with those of a "gold standard" test. "They did compare their device with gas chromatography and reported a strong correlation," he noted.
"That is good," Birnbaum explained. But he added that validity would be enhanced if independent researchers repeated that comparison. The device also needs to be tested on a larger number of people with varying levels of acetone in their blood and breath, he said.
In the future, Birnbaum said, if the device research bears out, it could provide people an additional piece of information. "It might help people stick with a diet; it might help them modify their diet."