PREDIMED study weighs in to dietary fat discussion

By Eleanor McDermid

A prespecified analysis of the PREDIMED study suggests that an increase in the proportion of calories consumed as fat in the context of a Mediterranean-style diet does not have an adverse effect on bodyweight.

"These results have practical implications, because the fear of weight gain from high-fat foods need no longer be an obstacle to adherence to a dietary pattern such as the Mediterranean diet, which is known to provide much clinical and metabolic benefit", say Ramon Estruch (University of Barcelona, Spain) and co-researchers.

The findings from the 5-year, randomised dietary intervention trial come at a time when dietary fat recommendations are a hotly contested issue, with, for example, the controversial reception of the UK National Obesity Forum's recent guidelines, which include the advice to eat more fat.

At study baseline, the 7447 participants, who all had Type 2 diabetes and at least three cardiovascular risk factors, consumed around 40% of their daily calories from fat - already higher than the current 35% average in the UK and the 30% recommended by the World Health Organization.

During the 5 years of the study, this proportion increased slightly to 41.8% and 42.2% in patients assigned to adopt a Mediterranean diet with supplementary olive oil (50 mL/day) and nuts (30 g/day), respectively, but declined slightly to 37.4% in those assigned to receive standard low-fat dietary advice.

But the somewhat higher fat consumption did not have an adverse effect on the participants' bodyweight or waist circumference, although these increased slightly in all three groups over the 5-year study.

Relative to the control diet group, the groups assigned to the Mediterranean diet plus olive oil and nuts, respectively, had bodyweight decreases of 0.433 and 0.075 kg, with the former being statistically significant. This was independent of variables including baseline body mass index, total energy intake and leisure-time physical activity.

Likewise, participants' average waist circumference reduced by 0.549 and 0.936 cm in the olive oil and nuts groups, respectively, versus the control group, with both of these changes significant after accounting for baseline variables.

"Overall, our results show that an increase in vegetable fat intake from natural sources in the setting of a Mediterranean diet had little effect on bodyweight or central adiposity in older individuals who were mostly overweight or obese at baseline", say the researchers.

Their current analysis, reported in The Lancet Diabetes & Endocrinology, is a prespecified secondary analysis of PREDIMED. The previously reported primary analysis showed that adherence to the Mediterranean diet had cardiovascular benefits for patients with Type 2 diabetes. The patients were aged around 67 years, on average, and almost all were overweight or obese.

Source: Lancet Diabetes Endocrinol 2016; Advance online publication

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