To review evidence relating to the consumption of whole grains and healthy body weight (BW).

Systematic review and analysis of observational studies reporting whole-grain consumption and measures of BW and adiposity, including the effect on macronutrient intakes and lifestyle factors.

Medline and other databases were searched for the period 1990 to 2006 to produce a full reference list; observational studies were retained for further analysis if they included an appropriate control group and reported whole-grain intake and body mass index (BMI) or a measure of adiposity.

Fifteen trials were identified which included data from 119 829 male and female subjects aged 13 years and over.

The combined and weighted mean difference in BMI from 15 studies representing 20 treatment groups (n = 119 829) using a random-effects model was 0·630 kg/m2 lower when high versus low whole-grain intake was compared, P < 0·0001 (95 % confidence interval (CI) 0·460, 0·800 kg/m2). In high consumers, adiposity assessed as waist circumference was reduced by 2·7 (95 % CI 0·2, 5·2) cm, P = 0·03 (six data sets, n = 4178) or as waist:hip ratio by 0·023 (95 % CI 0·016, 0·030), P < 0.0001 (four data sets, n = 20 147). Higher intake of whole grains led to increased dietary fibre intake (9 g, P < 0·01), while total and saturated fat intakes decreased by 11 g and 3·9 g, respectively.

A higher intake of whole grains (about three servings per day) was associated with lower BMI and central adiposity. In addition, people who consume more whole grains are likely to have a healthier lifestyle as fewer of them smoke, they exercise more frequently and they tend to have lower fat and higher fibre intakes.

The purpose of this overview is to synthesise and summarise the findings and recommendations of all 14 projects funded between 1997 and 2002 under Phase 2 of the Department of Health's Policy Research Programme Nutrition Initiative. This is aimed at end users, including policy makers, practitioners, researchers and research funding bodies.

The main findings and recommendations for policy and practice, as well as for future research, contained in the peer-reviewed final report of each project are summarised under headings identified as being useful for policy groups and practitioners: Maintenance of a healthy weight; Functional outcomes related to different markers of iron status; Nutritional aspects of bone health in humans; and Dietary interventions.

The overview draws together the key findings and recommendations for current and future policy and practice from the second phase of the research programme and identifies research gaps.

The findings and recommendations of the Department of Health's Nutrition Research Initiative have contributed to the scientific evidence base for policy development, policy evaluation, and will inform practitioners as well as researchers and research funding bodies.