tl;dr A feeble attempt to cover (cash in on) a story that was a misreported load of bull from the beginning.

The article justifies itself by referencing "recent reports in the popular media," i.e., we're too classy to report on fake fluffy science stories, we just do the public service of helping people understand them. But this article doesn't really help. If it wanted to help clear up the story, instead of nosing its way to the trough, it would have explained that the study was not designed to measure the effects of exercise on depression. In fact, exercise was one of the effects studied. To know that you don't even have to get past the abstract (http://www.bmj.com/content/344/bmj.e2758):

Main outcome measures: The primary outcome was self reported symptoms of depression, assessed with the Beck depression inventory at four months post-randomisation. Secondary outcomes included use of antidepressants and physical activity at the four, eight, and 12 month follow-up points, and symptoms of depression at eight and 12 month follow-up.

Whaaaa? What's going on here? The authors of the study helpfully explained it to the journalist, who opted to write the kind of article that would attract a lot of readers instead of an accurate one. But the journalist made a small concession to the truth by quoting the authors' explanation: "the new study simply recommended exercise of any kind – the authors explained that they 'asked a pragmatic question concerning a feasible intervention that could be used in primary care.'"

Sure enough, if you read the abstract, the study was designed to test the effectiveness of advice and education about exercise, not exercise itself:

Interventions: In addition to usual care, intervention participants were offered up to three face to face sessions and 10 telephone calls with a trained physical activity facilitator over eight months.

The key word in the authors' description of the study is "pragmatic." When it comes to lifestyle changes, non-doctors like us want to know, "What happens if I do X? Will it make a difference to my health?" Doctors are curious about that just like the rest of us, but professionally, the question they ask is, "What happens if I tell my patient to do X? Will it improve my patient's health?"

The answer is almost always "no," because patients almost never make lasting lifestyle changes. Knowledge about the effects of lifestyle changes is interesting and provocative, and worth passing on to patients, but a lifestyle change isn't a treatment that a doctor can administer. As the study says: "Numerous studies have reported the positive effects of physical activity but most of the current evidence originates from small non-clinical samples using interventions that are not practicable in healthcare settings." That's why studies like this exist: to test the treatments and services that health care professionals can provide to patients.

Unsurprisingly, the study yielded conclusions relating to the intervention it was designed to study:

The TREAD intervention was a pragmatic and acceptable intervention that could be implemented in the National Health Service and increase physical activity levels but had no impact on symptoms of depression.

The main implication of our results is that advice and encouragement to increase physical activity is not an effective strategy for reducing symptoms of depression.

Clinicians and policy makers should alert people with depression that advice to increase physical activity will not increase their chances of recovery from depression. (This is a hilarious recommendation. I am pretty sure that depressed people already know that getting advice does not cure depression. But hey, now we know from science.)

So much for "advice" and "encouragement." But we aren't doctors -- we want to know about the effects of exercise itself. The study did measure both exercise and depression as outcomes, so maybe they were able to draw some conclusions about the relationship between physical activity and depression. Hmmm....

Although our intervention increased physical activity, the increase may not have been sufficiently large to influence depression outcomes. The absolute difference between the randomised groups in terms of the proportion meeting our physical activity threshold was about 15% so there is still a possibility that physical activity itself might have some benefits for depression.

Also: A better understanding of the underlying mechanisms that might link physical activity and mood could lead to new therapeutic opportunities.

Ah. So the authors themselves don't believe the conclusion trumpeted in the headlines. It must have been some other researchers who drew such conclusions from the study. The BBC article does mention that some researchers have given critical attention to the study, so maybe they journalist found some who felt that stronger conclusions could be drawn about exercise? ... <crickets> Apparently not, though when I checked out the earlier media coverage, I found this one, single quote in all the articles:

"Exercise and activity appeared to offer promise as one such treatment, but this carefully designed research study has shown that exercise does not appear to be effective in treating depression."

That single statement is the basis of the ENTIRE media coverage of this article. As you might guess, it came not from a research article but from a Bristol University press release (http://bristol.ac.uk/news/2012/8529.html) Not only that, it came from one of the authors of the study! Seems like the first thing a journalist would do is ask him why his statement in the press release about the study contradicts the conclusions in the article he co-authored about the very same study. But that would ruin the story, wouldn't it?

Once again it seems that journalists can rise high in their profession by serving as an aggregation service for sensationalistic press releases, and some scientists are willing to openly whore for attention via non-peer-reviewed channels.