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.”

By comparison, obese study participants without diabetes reported more realistic eating habits, according to the researchers, led by Dr. Patrick Ritz.

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.

Diabetes Care, December 2006.

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DID YOU KNOW:
Perceptions of Obesity Varies by Race: Compared with overweight white Americans, overweight black Americans are two to three times more likely to say their weight is average -- even after they've been diagnosed as overweight or obese by a doctor, a new study finds. It's estimated that about 75 percent of black Americans are now overweight or obese. However, there's been less pressure for blacks to lose weight because of a cultural acceptance of higher body weight and heavier body shapes. International Journal of Behavioral Nutrition and Physical Activity