Yes, there is ample scientific and anecdotal evidence in favour of the fact that more vigorous exercise can cause weight loss. Therefore, the negative correlation that was established is quite valid. However, it also depends on the value of the coefficient of correlation to be able to say with a reasonable level of significance that walking causes lower weight. An alternate explanation for the finding can be that those people who were working in the company have cut down on their calories intake on the basis of a recent government campaign, which contributed more to the weight loss than walking.