Researchers from the University Hospital of Angers in France, led by Dr. Patrick Ritz, recruited 21 obese men and women, roughly half of whom had been diagnosed with type 2 diabetes. The researchers asked the diabetic participants to recall what they'd eaten over the past three days, then verified their actual caloric intake using a metabolic calculation technique called the doubly labeled water method.
Ritz and colleagues found that the diabetic participants reported eating one-quarter fewer calories than would be needed "even for basic functions to live," according to their report, published in the journal Diabetes Care.
However, obese participants who had not been diagnosed with type 2 diabetes were more accurate in reporting their eating habits, though Ritz's team was unsure why the non-diabetic men and women were more realistic.
The study's authors said physicians and dieticians should be made aware of diabetics' tendency to far underestimate their own caloric intake, since diet is a "cornerstone" of diabetes treatment and management. Doctors should be aware of a patient's true eating habits in order to advise dietary changes, the researchers said.
According to consumer health advocate Mike Adams, author of "The Food Timing Diet," gauging caloric intake accurately is "surprisingly difficult," even for people who are not obese.
"That's why it's so important to eat fresh product as meals or even snacks," Adams said. "Fruits and vegetables contain high amounts of water that make us feel full without burdening us with too many calories.