Self-reported food intake may thwart research

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Self-reported food intake may thwart research

Last Updated: 2004-03-22 16:36:20 -0400 (Reuters Health)

By Amy Norton

NEW YORK (Reuters Health) - A new study of overweight, diabetic women

casts doubt on the reliability of the self-reported dietary habits often

used in medical research.

Researchers found that most of the 200 women they studied, as many as 81

percent, reported eating fewer calories than they actually had, based on

objective measures.

Many also claimed to have eating habits that closely matched the

recommended diet for diabetics, which suggests the women were really

reporting what they thought they should be eating, according to the

researchers.

The problem with fibbing about or underestimating calories is that it

makes it hard to measure the true effectiveness of dietary

interventions--a key component of diabetes treatment. The new findings

point to the importance of using some objective measure to back up

research participants' dietary claims, the study authors report in the

March issue of the journal Diabetes Care.

Their study included middle-aged and older African-American women with

type 2 diabetes, most of whom were overweight or obese. Past research

has shown calorie underreporting to be common among women, people who

are overweight, and those who want to lose weight, lead study author Dr.

Carmen D. -Hodge told Reuters Health.

She said people may, for instance, have a hard time remembering what or

how much they ate, or may feel pressured to report eating habits that

are " socially acceptable. "

For the current study, -Hodge and her colleagues at the University

of North Carolina at Chapel Hill compared diabetic women's reported food

intake with objective estimates of their calorie expenditure. To get

these estimates, they had the women wear small electronic devices called

accelerometers, which gauge the number of calories burned during

physical activity, for one week. The researchers also measured the

women's base metabolic rates. These measures were compared with

participants' self-reported dietary intake on three days.

The idea is that in the absence of weight loss or gain, a person's

calorie intake should roughly equal calorie expenditure. If someone

takes in fewer calories than she burns, she should lose weight.

-Hodge and her colleagues found that most of the women in their

study reported calorie intakes that were lower than their estimated

calorie expenditure.

Based on the accelerometer data, the researchers estimate that 81

percent underreported their calorie intake. This estimate dipped, but

remained high at 58 percent, when the researchers compared calorie

intake with base metabolic rates.

The researchers also found that the heavier a woman was, the more likely

she was to underreport calories.

It's possible, the investigators acknowledge, that many of these women,

who were part of a larger study on managing diabetes with diet and

exercise, truly were cutting calories. But, they note, six months after

the current results were compiled, the women were showing no significant

weight loss.

The " major implication, " the researchers conclude, is that such

self-reports need to be independently validated.

-Hodge said the findings are particularly relevant to studies of

people with type 2 diabetes because of their high prevalence of obesity.

SOURCE: Diabetes Care, March 2004.

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