Williams PG, Grafenauer SJ, O'Shea JE. Cereal grains, legumes, and weight management: a comprehensive review of the scientific evidence. Nutr Rev. 2008 Apr;66(4):171-82.

To assess the evidence about the role of grains and legumes in the prevention and management of overweight and obesity, to ensure health messages are evidence-based and consistent with the best research available.

• Published in English
• Human studies
• Anthropometric outcome measures reported

• Original data not reported
• Only intermediate markers examined rather than direct measures of overweight and obesity
• Studies with a low quality rating, using methods and criteria of the European Heart Network, generally because they lacked control groups or the methods were inadequately described or validated

Recruitment

Literature search:

• Databases searched: PubMed, Medline, Scopus, Cinhal, Science Direct
• Dates included: 1980 - 2005
• Search terms: cereal, grain, wholegrain, legume, pulse, bread, pasta, rice, wheat, barley, oat, rye, soy, bean, pea in conjunction with obesity, overweight, satiety, BMI, waist
• References in identified papers also examined
• Relevant studies assessed for scientific quality using the methods and criteria described by the European Heart Network

Design: Comprehensive, systematic review

Blinding used (if applicable): not applicable

Intervention (if applicable): not applicable

Statistical Analysis: not completed

Timing of Measurements: not applicable

Dependent Variables

• Body mass index (BMI)
• Weight
• Waist circumference (WC)
• Waist-hip ratio (WHR)

Independent Variables

• Grain intake - as part of a dietary pattern or individual grain foods, including whole grain versus refined grains
• Legume intake

Control Variables

Initial N:

• Number of abstracts identified for review: N = 556
• Number directly relevant to topic: N = 121

Attrition (final N): Number of eligible studies after exclusion: N = 53

Age: not mentioned

Ethnicity: not mentioned

Other relevant demographics

Anthropometrics

Location: Authors - Australia

Key Findings

• There is good evidence from epidemiological and intervention studies that
  • a diet high in whole grains is associated with lower BMI;
  • a diet high in whole grains and legumes can help reduce weight gain; and
  • significant weight loss is achievable with energy-controlled diets that are high in cereals and legumes
• There is weak evidence that high intakes of refined grains may cause small increases in WC in women.
• There is no evidence that low-carbohydrate diets that restrict cereal intake offer long-term advantages for sustained weight loss.
• There is insufficient evidence to make clear conclusions about the protective effect of legumes on weight.

Epidemiological studies

Studies that analyzed dietary patterns (using principal components analysis or cluster analysis)

• Most studies found an association between a prudent dietary pattern with higher levels of cereals and legumes with lower measures of overweight, supporting recommendations to include these foods in a healthy diet
  • studies do not provide a clear consensus on
    • role of bread specifically
    • differing aspects of whole-grain versus refined cereals
    • dose-response data about the relationship
  • 11 studies identified
  • 10 studies found patterns that included higher intakes of whole grains to be associated with lower measures of obesity.
  • studies included both male and female subjects, age ranges = 8 to 87 years, in 12 different countries
  • one study found no association between BMI and quintiles of conformance to prudent diet with high intake of whole grains and legumes (Health Professionals Follow-up Study)

Cross-sectional studies

• Studies are consistent overall in demonstrating that higher intakes of whole-grain cereals and legumes are associated with lower BMI, WC and risk of overweight.
  • 1 major study showed a slight higher WHR (But not BMI) with higher consumption of refined grains
  • 3 other studies did not support that finding

Longitudinal studies of weight change

• Overall, results of longitudinal studies of weight change are somewhat inconsistent
  • Most studies have found an inverse relationship between whole-grain intake and weight gain
  • There is limited evidence in relation to legume intake.
  • A few studies found that higher intakes of refined grains appeared to be associated with increases in WC and BMI in women (weight changes < 0.7 kg over a 12 year period, statistically significant)
  • No studies were found that examined the association of high and low glycemic index grain consumption with body weight

Intervention studies

• There are few well-controlled studies that have specifically examined the effect of higher intakes of cereals and legumes on weight reduction or maintenance in the long-term, or compared the effects of refined- and whole-grain cereals specifically.
• Studies provide consistent evidence that weight loss is still achievable in diets that are high in cereals, especially the whole-grain variety
  • 17 intervention studies identified
    • 11 directly reported changes in weight or WC
      • Only a few (~4) studies reported a better rate of weight loss when the grain intake of the diet was increased.
      • All other studies demonstrated that a diet with high cereal content can support weight control, although most did not find a superior rate of weight loss when compared to diets with lower cereal intake levels.

Other Findings

Low carbohydrate diets

• 6 studies since 2003 have compared conventional and low-carbohydrate diets; duration = 3 to 12 months
  • over 6 months, slightly better weight loss (differences of 3.8 - 5.8 kg) reported with low-carbohydrate diet
  • after twelve months, the difference lost significance in those studies that followed participants longer

This research provides strong support for continuing messages to the public that a diet high in whole-grain cereals and legumes will support good overall health and is likely to help maintain a healthy body weight.