The New York Times gave this account of an experiment conducted to determine the noticible results of a six-week exercise program:

CARL FOSTER, an exercise physiologist...was amused by ads for a popular piece of exercise equipment. Before-and-after photos showed pudgy men and women turned into athletes with ripped bodies of steel. And it all happened after just 12 weeks of exercising for 30 minutes three times a week...

"We said: ‘Wait a minute. You can’t change yourself that much,’ " Dr. Foster said.  [He] recruited sedentary people for a six-week exercise program. Would objective observers notice any changes in their bodies? 

The plan was to photograph volunteers wearing skimpy bathing suits and then randomly assign them to one of three groups: cardiovascular exercise, weight lifting or control. Six weeks later, they would be photographed again.

Their heads would be blocked out of the photos, which would be shuffled. Then the subjects and judges would rate the body in each photo on a scale of 1 to 10, with 10 being spectacular.

The volunteers were men, age 18 to 40...And they were sedentary.

So, before reading any further:  what do you think happened?  Need I ask?

The question being posed by the experiment, it seems to me, is not whether exercise can make you look better in six weeks, but can NOT make you look better in six weeks? 

Thou need'st no ghost come from the grave to tell us this. 

Of course it can.  All you have to do is put a group of people on a crappy program, give them no dietary guidance, and wait around with your camera for six weeks, cackling wildly:  This will show them...exercise doesn't work!  It's all a sham! 

This seems like testing whether it's possible to build a light bulb that won't illuminate.

Here's how it (predictably) shook out, according to the article:

The subjects rated themselves more highly than anyone else rated them, and female panelists rated the subjects lower than the male subjects or panelists rated them. But, over all, the subjects’ ratings barely changed, if at all, after their exercise program. And neither did objective measures, like weight or percentage of body fat, or waist size or the size of the bicep or thigh.

I think it's funny that the guys in the experiment cut themselves some slack and rated each other relatively high compared to the brutally-honest women who rated them.  Perhaps they showed mercy to one another in hopes that the others would do the same? 

But the women let the guys have it but good.  A window into the precise degree of discernment with which the fair sex is evaluating us, eh, lads?

I digress.  The article goes on to suggest that it takes much longer than six weeks to make visible changes in your physique, and cites some inspiring examples of people who have lost lots of weight over years of effort.  

It's true that many of the physical transformations you see as part of the advertising materials for fitness products are nonsense. 

But in truth, six weeks is enough time--I'd even suggest plenty of time--to affect visible change in the body if the program is good, if there's a solid dietary component, and if the individual applies themselves.  

The study doesn't seem to be refuting the specific claims of any particular piece of advertising, just the notion that it's possible to change the way you look with exercise in a relatively short span of time.  And, shocker, it is tough to do.  And it's rare.  But impossible?  No way.