题目选项分析

Studies have demonstrated that people who keep daily diet records are far more successful at losing weight than people who don't keep track of what they eat. Researchers believe that this occurs because people who don't record their diets eat more calories than they intend to consume. One study followed a group of patients who reported that they could not lose weight when consuming only 1,200 calories a day. The study found that the group consumed, on average, 47% more calories than it claimed and exercised 51% less. In contrast, when dieters record what they eat, their actual consumption more closely matches their reported consumption.

The two boldface portions in the argument above are best described by which of the following statements?

【选项】 The first demonstrates a cause-effect relationship discovered by the researchers; the second is the basis for the researchers' argument.