New research suggests that obese adults with diabetes often say they eat less than they actually do - a problem that can hinder management of the disease, according to researchers.

Their study of 21 obese men and women found that all of those with type 2 diabetes reported eating far fewer daily calories than objective tests suggested they did.

Researchers caught the erroneous reporting by using a sensitive measure of metabolic rate known as the doubly-labeled water method. All of the study participants had a stable weight, which would be maintained when the amount eaten equals the calories burned each day.

But on average, diabetic adults reported a calorie intake that was nearly one quarter lower than they would need “even for basic functions to live,” the study authors report in the journal Diabetes Care.

By comparison, obese study participants without diabetes reported more realistic eating habits, according to the researchers, led by Dr. Patrick Ritz of the University Hospital of Angers in France.

The researchers tested the reliability of the study participants’ reports on their diet by having them recall what they’d eaten over the previous three days; they then calculated each person’s estimated daily calorie intake and compared that with the metabolic rate.

It’s not clear why diabetics were less accurate in their food reports than their non-diabetic counterparts, according to Ritz’s team. But they say doctors and dietitians should be aware of this tendency.

Honesty about eating habits is vital, as diet is a “cornerstone” of managing diabetes, the researchers point out. Doctors need to know a patient’s true eating habits not only to help devise a better diet, but to figure out which eating patterns might be behind any problems in diabetes control.

SOURCE: Diabetes Care, December 2006.