Does a low-calorie meal pay off? some dieters say that eating less at just one meal is ineffective, because people compensate by eating more at other meals, but a new study contradicts that argument. below is an excerpt from a ny times article on this study:

"for two weeks, researchers had 17 men and women eat all their meals and snacks, as much as they wanted, at a buffet where the exact quantities consumed could be weighed and caloric intake calculated. then for the next two weeks, the participants ate a 200-calorie lunch, a commercially available food like a kashi bar or a lean pocket. but the rest of the day, they ate whatever they wanted from the buffet.

not counting lunch, the participants consumed 1,568 calories on days they had the 200-calorie lunch and 1,560 on days when they did not - an insignificant difference. but over all, they consumed 245 fewer calories on low-calorie lunch days. the result of that - unsurprisingly - was weight loss: an average of 1.1 pounds per participant in two weeks."

what type of study is this?

(a) experiment
(b) observational study