In Massachusetts, Tufts University researchers reported that people who ate a diet with whole grains, which matched the recommended dietary allowance for fiber, lost close to an extra 100 calories per day. The study suggests that substituting whole grains for refined grains in the diet increases calorie loss by reducing calories retained during digestion and speeding up metabolism.
Previous epidemiology studies have suggested certain health benefits of whole grains and high dietary fiber intake; however, questions about whether whole grains and fiber are beneficial for weight regulation have persisted, partially because there hasn’t been data from controlled metabolic studies.
The researchers caution that the effects of a whole grain diet on resting metabolic rate were sensitive to dietary adherence, so cautious interpretation is warranted. Based on previous research and current study measurements, however, they believe that the calorie loss was not due exclusively to the digestion of extra fiber intake.