The relationship between dietary fat and fatty acid intake and body weight, diabetes, and the metabolic syndrome

Abstract

In this review, we have summarized studies published between 1993 and the present that have addressed the associations between dietary fat intake and obesity, the metabolic syndrome and diabetes. With regard to obesity, although there is a substantial body of data suggesting that there is an association between total fat and saturated fat intakes and body weight, there are nearly as much data suggesting that there is no association. Thus, we conclude that the data on the association between total fat intake and saturated fat intake and body weight remain inconclusive. Interventional randomized studies comparing the Atkin's diet to other regimes - with percentage of fat being the primary difference and similar overall intensity of intervention - tend to show a greater weight loss than lower fat diets. However, the usefulness of these results is limited by differences in other macronutrients and high drop-out rates. Larger intervention studies suggest that lower dietary fat is associated with weight loss; however, the studies were not designed to specifically examine dietary fat and weight, and thus differences in intervention intensity make it impossible to draw definitive conclusions from these results. Systemic studies of trials and meta-analyses suggest that diets lower in fat and with calorie restriction are associated with greater weight loss, but these interventions have typically been of limited duration or involved additional lifestyle changes (e.g. an increase in physical activity). Although many prospective cohort studies show a positive relationship between dietary fat intake and weight gain, these data are also inconclusive. From our review, we also conclude that there is insufficient evidence - due to the small number of studies - to determine whether there is a relationship between intake of MUFAs or PUFAs and body weight. We also conclude that there is insufficient evidence at this time to determine the association between diabetes risk and intake of total fat or of any particular type of fat. However, there are a sufficient number of studies that suggest that total fat and saturated fat intakes increase the risk of having components of the metabolic syndrome, and that higher intakes of MUFAs and PUFAs have a beneficial effect in reducing this risk. © 2009 S. Karger AG, Basel and FAO.