Grains and Weight Management

Of the developed nations, Australia is one of the most overweight, with more than 60% of adults and one in four children overweight or obese. The prevalence of overweight and obesity in Australia has been steadily increasing during the past 30 years and if the current trends continue unabated, it is estimated that nearly three-quarters of the Australian population will be overweight or obese by 2025. While evidence suggests that rates of overweight and obesity may be reaching a plateau in children, the prevalence in Australia is still higher than is desirable.

It is well recognised that a diet high in whole grains, fibre and legumes promotes good health.

Long-term observational studies demonstrate that people who include whole grain and/or high fibre grain foods are less likely to gain weight over time. Two reviews of the evidence on grain foods and weight have been published in the last five years and conclude that higher intakes of grain foods, particularly whole grains and/or high fibre, are associated with lower BMI, smaller waist circumference and less weight gain.

A word on low carbohydrate diets:
The popularity of high protein low carbohydrate diets has led some people to cut out all grain foods to lose weight. However, research shows that effective higher protein diets for weight loss and weight maintenance recommend moderate carbohydrate intakes and approximately 4 serves of grain foods each day, with preference to whole grain, high fibre and/or low glycemic index (GI), as part of a nutritionally balanced weight loss diet.

In summary, restricting grain foods, particularly whole grain or high fibre grain foods, within a low carbohydrate diet does not appear to offer long term advantages for maintaining a healthy weight. In fact, rather than promoting health and a healthy weight a recent review found that long term exposure to a low carbohydrate diet increased risk of mortality.

“Whole grains are an important part of a healthy higher protein diet for weight management which is why the CSIRO Wellbeing diet recommends at least 3 serves of whole grains per day.”
Professor Manny Noakes, Research Program Leader CSIRO Food, Nutrition and Health Science

Suggested Mechanisms

Fibre: It is believed that the higher fibre content of diets rich in whole grains is one of the main mechanisms through which they help control body weight. Dietary fibre can assist weight control in the following ways:

  • higher fibre whole grain foods are typically less energy dense than refined foods;
  • the bulking properties of dietary fibre promote satiety;
  • high fibre whole grain foods typically (but not always) have a lower GI, which slows the rate of starch digestion leading to lower blood glucose and insulin levels after a meal; and
  • fibre increases chewing, which increases saliva and gastric juice production. This expands the stomach and helps to satisfy the appetite sooner.

Metabolic Effects: In the Health Professionals Follow up Study, associations between whole grain intake and reduced weight gain were attenuated after adjustments were made for micronutrients like magnesium, and they persisted even after bran and fibre intakes were accounted for, implying additional metabolic effects beyond the effect of the fibre content. This suggests there are additional components in whole grains that may contribute to metabolic alterations which favour long-term weight management.

To assist health care professionals in communicating to their clients click on the following link to access the consumer information resource on Grains & Weight Loss‘.

To view references click here.

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