From the Guidelines
Consuming whole grains as part of a balanced diet can assist in weight loss, with a recommended intake of 3-5 servings daily, as supported by the most recent and highest quality study 1. The evidence suggests that whole grains can help with weight management through several mechanisms, including increasing satiety and reducing hunger due to their high dietary fiber content.
- Whole grains like oats, brown rice, quinoa, and whole wheat are rich in dietary fiber, which helps slow digestion and maintain stable blood sugar levels, preventing spikes and crashes that can trigger hunger.
- The fiber in whole grains also requires more energy to digest than refined grains, slightly increasing calorie expenditure.
- Additionally, whole grains generally have a lower glycemic index compared to refined grains, meaning they cause a more gradual rise in blood sugar. The study 1 found that consuming 2-3 servings per day of whole grains, approximately 48g, may reduce the risk of cardiovascular disease, type 2 diabetes, and overweight and obesity.
- The evidence also suggests that those who consume an average of 3-5 daily servings of whole grains have a 21-30% reduction in risk of type 2 diabetes compared with those who rarely or never consume whole grains. For best results, replacing refined grain products with whole grain versions rather than simply adding whole grains to the existing diet is recommended, as this substitution approach helps reduce overall calorie intake while improving nutritional quality 1.
From the Research
Evidence for Whole Grains in Weight Loss
- Epidemiological studies consistently demonstrate that higher intakes of whole grains are associated with lower body weight and reduced risk of obesity 2, 3, 4, 5.
- The potential mechanisms whereby whole grain intake may help reduce overweight include lower energy density of whole grain based products, lower glycemic index, fermentation of non digestible carbohydrates, and modulation of intestinal microflora 2.
- Clinical trials have failed to support a role for whole grains in promoting weight loss or maintenance, possibly due to small sample size, short duration of the intervention, or heterogeneity in study design 2, 4, 5.
- A randomized clinical feeding trial found that a weight loss diet rich in whole grains had a more beneficial effect on cardiovascular disease risk factors than diets rich in fruits and vegetables or a combination of whole grains and fruits and vegetables 6.
Limitations and Future Directions
- Further intervention studies with adequate methodology are needed to clarify the relationship between whole grain consumption and weight loss 2, 5.
- Studies should use a consistent definition of whole grain foods and examine the effects of different types and amounts of whole grains on weight management 5.
- The lack of consistency in intervention studies may be partly explained by heterogeneity in study duration, population, and sample sizes 5.