Although a variety of other weight loss drugs exist, only 22 randomized controlled studies of fluoxetine, orlistat and sibutramine met the high standards set by the researchers for inclusion in the review.
Of the 22 studies reviewed, the drugs' manufacturers paid for 18 of them and did not provide the reviewers with unpublished studies the companies had done on each of the included drugs, Norris says.
Norris says there is only a small amount of data on other weight loss drugs and people with type 2 diabetes. For instance, the researchers did not find any good studies examining the effects of popular weight loss drugs like ephedra in diabetic patients.
Obesity has been closely linked with type 2 diabetes. In a 2000 study, 80 to 90 percent of people with type 2 diabetes are overweight. Obesity may also worsen problems associated with diabetes, including high blood sugar, high cholesterol and high blood pressure, say Norris and colleagues.
Norris says people with diabetes who are also overweight may have a harder time losing weight than non-diabetics.
Insulin therapy itself might cause weight gain, Norris says. Keeping track of a complex series of treatments for diabetes, high cholesterol and high blood pressure "all complicate behavioral change aimed at weight reduction."
Recommendations by the American Diabetes Association in 2002 say that weight loss drugs may be useful in treating obesity among type 2 diabetes patients, but also note that "these drugs work best in conjunction with lifestyle strategies" such as low fat diets and increased exercise.
Norris and colleagues say more research is needed to find out whether weight loss drugs work better when combined with diet and exercise changes.
"In general populations, drugs have been combined with various lifestyle interventions, but most [drug] trials include relatively weak lifestyle programs, perhaps in
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Contact: Susan Norris
snorris@cdc.gov
Center for the Advancement of Health
17-Feb-2005