The World Health Organization (WHO) Global InfoBase Online offers a way to compare up to eight nations' statistics on a bar graph. It does not offer multi-year information. The obesity information (measuring Body Mass Index) available is from 2004.
There are statistics for the EU countries (from different years of collection) in the International Obesity Task Force's EU Platform Briefing Paper (March 15, 2005) (in PDF). Note that the report warns that "[f]ew countries conduct systematic measured surveys to obtain reliable nationally representative data to assess the degree of overweight and obesity in their populations. Self reported surveys tend to significantly underestimate the scale of the problem." You can also go to the database for the IOTF. The IOTF is part of the International Association for the Study of Obesity.
There will be increasing amounts of information on the European Health Information Platform. Try searching the site by keywords "obesity" or "body mass index."
If you want to attempt statistical research by country, the WHO also lists "Links to National Health-Related websites (Health Ministries and Central Statistics Offices, where available)."
Here are some recent articles that you may find useful. Go through your local public library's databases to try to find the full text or, if you're affiliated with a college or university, try their electronic resources.
Haslam, David W., and W. Philip T. James. "Obesity.(Seminar)." The Lancet 366.9492 (Oct 1, 2005): 1197(13).
Ellaway, Anne, Sally Macintyre, and Xavier Bonnefoy. "Graffiti, greenery, and obesity in adults: Secondary analysis of European cross sectional survey." British Medical Journal 331.7517 (Sept 17, 2005): 611(2).
Lissau, Inge, Mary D. Overpeck, June Ruan, Pernille Due, Bjorn E. Holstein, and Mary L. Hediger. "Body mass index and overweight in adolescents in 13 European countries, Israel, and the United States." Archives of Pediatrics & Adolescent Medicine 158.1 (Jan 2004): 27(7).
Europe fattens up
Anonymous. New Scientist. London: Mar 11-Mar 17, 2006.Vol.189, Iss. 2542; pg. 6, 2 pgs
Europe's Turn To Wrestle With Obesity
Paul Meller. New York Times. (Late Edition (East Coast)). New York, N.Y.: Nov 24, 2005. pg. C.5
European kids follow U.S. lead . . . to obesity; [Home Edition]
SHELLEY EMLING. The Atlanta Journal - Constitution. Atlanta, Ga.: Jun 9, 2005. pg. B.1