Whole grain foods contain the same bran, germ and endosperm ratios as the original plant material, and this gives them a high fibre and high nutrient content. Evidence suggests that including more whole grains in the diet is protective of obesity. While calorie restriction and exercise are generally ineffective in long-term weight loss, strategies to improve diet quality through education and exchange of energy dense nutrient poor foods for high fibre nutrient dense foods are effective in promoting weight loss or preventing weight gain. As well as promoting satiety because of their high fibre content, whole grain food also slow digestion and absorption of macronutrients, which can have favourable effects on plasma glucose and insulin levels. The effects of whole grains on weight changes over time have been studied by researchers using repeated measures of grain intake and body weight.
Using data collected from 74 091 US female nurses aged 38 to 63 years between 1984 and 1996, researchers1 investigated how whole grains affect weight gain. Food frequency questionnaires were taken in 1984, 1986, 1990 and 1994, and these were used to assess the amount of whole grains in the diet. Body mass index, weight changes and the odds ratio of developing obesity were calculated from data collected from the subjects during the study. The researchers found that the women who consumed more whole grains weighed less than women who ate fewer whole grains. Over the length of the study (12 years), those with the greatest increase in intake of dietary fibre weighed an average of 1.52 kg less than those with the smallest increase in intake. Women with the highest intake of dietary fibre had a 49% lower risk of major weight gain than women with the lowest intake.
The results from this study suggest that weight gain is inversely correlated with intake of fibre and whole grain foods. Alternative it could be stated that eating refined carbohydrate foods is associated with weight gain. This supports previous studies and suggests that dietary choices are important in maintaining a healthy weight. Interestingly, the study found that increases in dietary fibre were most effective in reducing weight gain in subjects who were overweight at baseline. Refined grains may promote weight gain because they cause larger increases in insulin, which over time may shift metabolic fuels from oxidation to storage. Refined grains may also be associated with less satiety, because the foods generally contain less bulk and have faster digestion. Incorporating more high fibre whole grains foods is an effective strategy in weight control.
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