Some researchers did a study of other studies to try to determine what effect exercise has in reducing the risk of chronic disease in fat people. I will admit, I am not going to pay to read the full research paper.
In the abstract summary, the researchers say that exercise offers only a modest reduction in chronic disease risk for fat people.
I found that confusing because I believe that recently there has been quite a bit of research to the contrary. So first, I have to wonder what studies were these guys looking at. Recently may be part of the problem because part of the researchers’ criteria was to use studies dating before March 2010.
Other criteria included that the trials had to be randomized, at least 10 weeks duration, with a sample mean body mass index of greater or equal than 30, and the study had to report on things like blood pressure, blood lipids, glucose/insulin or C-reactive protein. Note – the study had to report on at least one of those factors, not all of them.
The researchers admit that there was a great “heterogeneity” (consisting of dissimilar elements or part) in responses to risk factors across the studies and the types of exercise used was heterogenous across the different studies. So lots of different kinds of exercise and lots of different responses.
And there was a problem in differentiating the effect of the physical activity independent of weight loss. In other words, what was causing the effect – losing weight or the physical activity?
The abstract summary concludes with: “The degree to which physical activity is effective at lowering risk factor levels among high-risk obese individuals is not known.”
Seems pretty clear. Basically they are saying “I don’t know.”
I don’t find that surprising, considering how many variables they were dealing with in looking at 44 different studies conducted by different researchers for different purposes.
How do you get from “Overall, physical activity had no more than a modest effect on chronic disease risk factors in obese individuals” to “The degree to which physical activity is effective at lowering risk factor levels among high-risk obese individuals is not known.” These statements seem to be contradictory.
“I don’t know” is a perfectly acceptable answer.
http://www.doctorslounge.com/index.php/news/pb/23691
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-789X.2011.00933.x/abstract
Fatties United! 
Because they think they have to say something & because the subject is fat, they think they have to say something negative, & because I am reasonably certain that they didn’t search too deeply & that they likely were only looking for anything which would suggest that there is nothing fat people can do to improve health except lose weight, or that fat people are incapable of being fit or healthy, which most of us fat people know for ourselves is bullshit.
They cannot find a 30-year study of 30,000 or more people at the Cooper Institute which showed that fat fit people are as healthy as fit thin people & have as low risk of disease as fit thin people, etc., & many studies which have indicated that fat people do not necessarily have higher disease risks, etc., & especially that regular moderate movement (exercise is often a negative word to many of us) is beneficial to people of all sizes & shapes? Now that I think about it, considering how little impact exercise generally has on people’s weight (personal experience amplifies this, numerous experiences, most recently a four-year period of increasing my daily exercise to 4 hours per day & losing a grand total of 18 pounds in 4 years), perhaps what they REALLY mean is that exercise is not shown to result in much WEIGHT LOSS in ‘obese’ people, which, as we all known, is translated in the minds of many researchers into ‘having no benefit.’
And, as you say, there is no shame in saying you do not know. However, it doesn’t help you get more research grants.
If they really wanted to know, they’d do a real study rather than a data dredge.
You know, I have the same feeling about these “studies” which are really just “cherry-picking” data from other studies. Like statistics aren’t malleable enough, now you are adding, as you say, dredging data from other studies.