The trial on middle-aged men found increased consumption of wholegrains to be inversely related to weight gain even after changes in added bran or fibre intakes were accounted for.
"This suggests that additional components in whole grains may contribute to favourable metabolic alterations that may reduce long-term weight gain," reported the researchers in this month's American Journal of Clinical Nutrition (vol 80, no 5, 1237-1245).
The team from Harvard School of Public Health and other US universities noted that studies investigating wholegrain consumption in relation to weight gain have been obscured by methodologic inconsistencies in the assessment of whole grains.
They used new quantitative estimates of wholegrain intake to analyse data from a prospective cohort of 27 082 men aged 40-75 years old, following them for eight years.
They observed a dose-response relationship between wholegrain intake and long-term weight gain : for every daily 40g increment in wholegrain intake from all foods, weight gain was reduced by 0.49 kg. Bran that was added to the diet or obtained from fortified-grain foods as well as fruit and cereal fibre further reduced the risk of weight gain, said the researchers.
However no associations were observed between changes in refined-grain or added germ consumption and body weight.