Dietary Guidelines for Americans recommend eating a nutrient-dense breakfast to promote calorie balance and weight management, since not eating breakfast has been associated with excess body weight. A team led by David Allison, Ph.D., associate dean for science in the UAB School of Public Health, said that studies designed to find links between two things, like breakfast habits and obesity, often do not prove that one causes the other.

Andrew Brown, Ph.D., first author of the new study recently published online in the American Journal of Clinical Nutrition, spearheaded the examination of 92 studies about the proposed effect of breakfast on obesity (PEBO). The PEBO-related research literature, the authors found, seemed to be influenced by factors that led to exaggerated beliefs and statements about the purported effects of breakfast consumption on obesity. These include research that lacks probative value and biased research reporting.

Probative value is the extent to which a study can move knowledge forward from the current status quo. The authors explain that probative value of a given study on a topic tends to decrease as similar types of studies are repeated excessively.

"Another way to look at it is to ask, 'Do we really feel any more confident about the relationship between skipping breakfast and obesity after the 78th compared to the 77th cross-sectional association study,''' Brown said.

Biased research reporting, the authors explain, entails distorting research findings in ways that support a particular hypothesis beyond what the data support.

"We specifically found that research articles tended to overstate the strength of study designs and ignored evidence that did not support the proposed effect of breakfast on obesity," Brown said. "These distortions leave readers believing that the relationship between breakfast and obesity is more strongly established by science than the data actually support."

Allison and his team, which included Brown and Michelle Bohan Brown, found that scientists collectively do not know as much about the relationship between skipping breakfast and obesity as previously thought, based on the current state of PEBO-related research.

Their meta-analysis indicated that there is certainty that breakfast-skipping and obesity are associated, but it cannot confirm whether there is a causal effect of skipping breakfast on obesity.

"Although we know that breakfast-skippers are more likely to be overweight or obese, we do not know if making breakfast-skippers eat breakfast would decrease their weight," Brown said. "Nor do we know if making breakfast-eaters stop eating breakfast would cause them to gain weight."

"Uncertainty should not be confused with evidence of no benefit or harm, though," Allison aid. "It just means that right now we don't know how changing breakfast-eating habits will influence obesity -- eating versus skipping breakfast could help control weight, cause more weight gain or have no effect -- and the effect may vary from person to person."