In a large United States study 27,082 men aged 40-83 years were periodically questioned on a variety of lifestyle factors. Over an eight-year period, the participants completed self-reporting questionnaires regarding medical history, dietary intake, physical activity, age, height, weight, smoking history, and marital status.
Dietary intakes were recorded and the percentage of wholegrain in foods was analysed: breakfast cereals (37.6%), brown rice (25.3%), cooked oatmeal (21.8%), and popcorn (11.6%). Bran, wheatgerm and other fibres were also investigated for their role in weight management.
The team of researchers found that an increase in wholegrain intake helped reduce long-term weight gain. For every 40g daily in wholegrain intake from all foods, weight gain was reduced by 1.1kg. Bran that was added to the diet or obtained from fortified-grain foods further reduced the risk of weight gain and for every 20g daily increase in intake, weight gain was reduced by 0.36kg. Changes in cereal and fruit fibre also helped to reduce the risk of weight gain.
This could not be said for refined grains where the risk of weight gain could not be ruled out. Refined grains included grain foods with less than 25 per cent wholegrain or bran content by weight, such as some breakfast cereals, refined wheat flour breads, white bread, English muffins, bagels, pancakes, waffles, white rice, pasta, cookies, doughnuts, brownies, sweet cakes and pizza.
Men who consumed the largest amounts of wholegrain foods also tended to have a lower body mass index (BMI) rating, were less likely to smoke and were more physically active. Higher intakes of wholegrains were associated with lower intakes of total fat, saturated fat, dietary cholesterol and alcohol, and higher intakes of dietary fibre, magnesium, vitamin E, vitamin B6, and folate.
In this population of men, an increase in consumption of wholegrains, especially from foods that contain at least 25 per cent or more wholegrain or bran, protected against long-term weight gain.
Also see our article on low GI foods.
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