More proof: crunches alone won't give you a sixpack
Hundreds of thousands of men and women are still doing crunches till they're blue in the face, with or without miracle machines from Tell Sell, in the hope of gaining a slimmer waist or a washboard. Impossible, say trainers. And a study published in the Journal of Strength and Conditioning Research proves them right again.Localized fat loss
No, say trainers, you can't lose fat in specific places by training. You can only lose fat. If you are burning more energy than you consume via food, your body breaks down fat everywhere it can, and sooner or later you'll see the benefits in the places you most want to see the fat melting away.

Researchers have done countless experiments in which subjects do sit-ups and crunches, and measured the amount of subcutaneous fat that disappeared around their waste - with no result.
American sports scientists repeated these studies briefly by getting 14 non-active people in their twenties with stable bodyweight to train their abdominal muscles for six weeks consecutively. The subjects had to do a workout for their middle section five times a week. The workout consisted of seven exercises, with two sets of ten reps for each.A control group of ten people in their twenties did nothing in those six weeks.
Results
The table below shows that the ab training [Exercise] did not result in any statistically significant changes in the bodyweight, total fat mass or the android fat mass. Android fat is the fat in the torso: around the abdomen, chest, shoulders, neck and back. At the end of the six weeks the test subjects were capable of doing more crunches.









Conclusion
"Abdominal exercise training was effective to increase abdominal strength but was not effective to decrease various measures of abdominal fat", the researchers conclude.

"Some individuals attempt to reduce their waistline by solely performing abdominal exercises possibly because of claims made by various abdominal equipment advertisements. The information obtained from this study can help people to understand that abdominal exercise alone is not sufficient to reduce waistline or subcutaneous abdominal fat."
Source:
J Strength Cond Res. 2011 Sep;25(9):2559-64.