Abdominal adiposity: a stronger marker to predict survival

Body mass index (BMI^a) is normally used in epidemiological studies as a marker of total adiposity, whereas waist circumference (WC^b) is used as a marker of body shape and fat distribution. Recent epidemiological studies have demonstrated that when both WC and BMI are included simultaneously in statistical models, WC adjusted for BMI (or “WC for a given BMI”) is more strongly related to disease risk than BMI or WC alone. For instance, among individuals with the same BMI, even within the normal range of BMI, those with higher WC showed a lower survival, suggesting that “WC for a given BMI” may capture the specific effect of the abdominal fat mass¹. Given the widely recognized effects of abdominal adiposity on health, the understanding of how diet can modulate changes in the phenotype “WC for a given BMI” (WCBMI) is deemed necessary. The aim of the present study was to ascertain the association between specific food groups/items consumption and changes in WCBMI, i.e. changes in WC that are independent of concurrent changes in BMI.

The current study² included participants from five countries involved in the European Prospective Investigation into Cancer and Nutrition (EPIC) study, participating in the DiOGenes (Diet, Obesity and Genes) project, namely Italy, United Kingdom, the Netherlands, Germany and Denmark (n = 48,631). At Baseline (between1992–1998), participants filled out extensive questionnaires covering their diet, lifestyle, and medical history, and anthropometric measurements were obtained. Updated information on anthropometric data has been obtained from EPIC participants through follow-up examinations during 1998–2005 (median follow-up time 5.5 years). The outcome of interest in the present study was the change over time of WC that is independent of the concurrent change in BMI, i.e. gains in WC over and above a given gain in BMI, likely to represent the specific accumulation of abdominal fat mass. For that we defined the phenotype WCBMI (cm/year) both at baseline and at follow-up as the residual values from the gender- and centre-specific regression equations of WC on BMI^c. Annual changes in this phenotype (ΔWCBMI) were calculated as (follow-up WCBMI – baseline WCBMI) / follow-up time³. The association between dietary variables and ΔWCBMI (in cm/year) was modelled using multi-adjusted linear regression analyses.

Higher consumption of fruit and dairy lowers the increase of abdominal adiposity

Of all food groups considered, six food groups were found to be significantly associated with ΔWCBMI in a consistent way in both men and women. Fruit and dairy product consumption were inversely associated with gains in WCBMI, indicating that a higher consumption of fruit and dairy was associated with a lower increase of abdominal adiposity. On the other hand, consumption of white bread, processed meat, margarine, and soft drinks were all positively associated with ΔWCBMI, indicating that higher consumption of these foods was associated with greater gains in abdominal adiposity. The lowest gain of abdominal adiposity was observed when either dairy products or fruits substituted the consumption of softdrinks. In order to better translate these findings into public health messages that encourage overall healthy diets we constructed a summary score of our results. Overall it was estimated that those following a diet characterized by high fruit and dairy products and low white bread, processed meat, margarine, and soft drinks consumption, would show 1.1 cm less gain in WC for a given gain in BMI during a 10 years period, compared to those with a diet with opposite characteristics.

A whole dietary pattern for a lower accumulation of abdominal fat mass

In the present study we have observed that among European men and women, a dietary pattern characterized by a high consumption of fruits and dairy products, and a low consumption of white bread, processed meat, margarine, and soft drinks was associated with a lower gain in WC independently of concurrent gains in BMI, likely to represent a lower accumulation of abdominal fat mass. In addition, this study supports that a whole dietary pattern incorporating simultaneously several food recommendations may yield further benefits on health – in this case prevention of abdominal fat accumulation, compared to the effect of its single components, and hence recommendations should encourage an overall healthy diet.

a. BMI is calculated as weight in kg divided by the squared height in meters.
b. WC in cm is normally measured at the waist line using a tape.
c. Calculating the residuals of WC regressed on BMI is a way of adjusting WC for BMI.