Reducing your total calorie intake, not eating whole grains, causes weight loss. A study published in 2008 in the “American Journal of Clinical Nutrition” found that participants who followed reduced-calorie diets containing whole grains lost the same amount of weight as study subjects who consumed reduced-calorie diets containing refined grains -- such as white bread. However, although weight loss was similar in both groups, participants who consumed whole grains had higher reductions in abdominal fat mass compared with study subjects who ate refined grains. Translation: just eating whole grains won't change the number on the scale, but they'll help whittle your waist.
One reason whole grains are beneficial for healthy weight management is they are generally higher in fiber than refined grains. A study published in 2013 in “ISRN Obesity” reports that dietary fiber enhances satiety and reduces hunger, making fiber beneficial for weight loss. However, researchers who conducted this study report that the fiber intakes of people following reduced-calorie diets often fall short of meeting daily fiber requirements of 25 to 35 grams daily. For best weight-loss results, aim to consume fiber from whole grains, legumes, fruits, vegetables, nuts and seeds. One cup of cooked oatmeal provides 3.2 grams of fiber, 1 cup of brown rice contains 3.5 grams and two slices of whole-wheat bread provide 3.8 grams of dietary fiber.