Study: Current dietary guidelines give wrong idea about effects of consuming Mediterranean diet fats

A Mediterranean diet which is rich in vegetal fats (extra virgin olive oils, dried fruit and nuts, etc.) does not mean it comes with weight gain if compared to a low-fat diet, according to a study published in the medical journal The Lancet Diabetes & Endocrinology. This work suggests that lots of current guidelines on health giving advice on reducing fat and calories give a wrong idea of the effects of consuming Mediterranean diet fats, a diet with well known health benefits.

The article is signed by the experts Ramon Estruch (Faculty of Medicine and Health Sciences of the UB and Hospital Clínic de Barcelona), Emili Ros (Hospital Clínic de Barcelona and IDIBAPS), Rosa Maria Lamuela (Faculty of Pharmacy, UB) and Xavier Pintó (Faculty of Medicine and Health Sciences of the UB and IDIBELL), among other experts from institutions and hospital centres from all the country.

The scientific evidence indicates that the total amount of lipids is not the best indicator to value the negative or beneficial effects of the food. Along these lines, dried fruit fats, fish and vegetal oils rich in phenolic compounds are healthier than the lipids from meat and processed foods.

Mediterranean diet and healthy fats

"More than forty years of nutritional policy advocated for a low calorie diet but we are proving that it has little impact on controlling obesity levels", says Ramon Estruch, first author of the study and member of the Spanish Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBERobn) of the Institute of Health Carlos III. "Our study shows that a high-fat Mediterranean diet with olive oils and dried fruits has little impact on weight or abdominal perimeter compared to the effects on a low-lipid diet. The Mediterranean diet has well known health benefits and it has healthy fats (vegetal oils, fish and dried fruits)" says Estruch. Our findings do not mean, however, that restricted diets with high levels of unhealthy lipids (butter, processed meats, sugared drinks, deserts or fast food) are beneficial.

Obesity is a risk factor for several pathologies (cardiovascular diseases, type 2 diabetes, cancer, musculoskeletal disorders, etc.). To prevent people from obesity, it is good to exercise regularly and eat a low-fat diet: up to a 30% of lipids of the total consumption of energy, according to the recommendations from the World Health Organization (WHO) and other international entities. Several studies have stated that the Mediterranean diet -including healthy fats- can help reducing health risks. However, prevention of eating fats makes it more common to suggest low-lipid diets to lose weight.

The new studied included 7.447 participants (male and female, aged between 55 and 80) and it was carried out in eleven hospitals around the country during the years 2003-2010. The participants were divided into three groups according to a different nutrition they had: a non-calorie-restricted Mediterranean diet, rich in olive oils, a Mediterranean diet without calorie restrictions and rich in dried fruits, and a total low-fat diet. All participants had a high cardiovascular risk or were diabetic (type 2), and more than the 90% suffered from obesity.

After 5 years, the total fat consumption was reduced to the low-lipid diet group while it had slightly increased in the other two groups that were on a Mediterranean diet. According to the results, all participants lost weight: the ones who lost more weight followed the non-calorie-restricted diet which was rich in olive oils. Regarding abdominal perimeter, it increased in the group that were on a low-fat diet, compared to groups with Mediterranean diet.

In a comment to the scientific article, Professor Dariush Mozaffarian (Tufts University, Boston) highlights that "dietary guidelines should be revised to erase arbitrary and obsolete limits on the total fat consumption. Prejudices and warnings on healthy and fat options should also be removed, such as dried fruits, vegetal oils rich in phenolic compounds, yogurt and even cheese. We have to forget about the myth that says low-fat and low-calorie foods lead to a lesser weight gain. This thought turns into paradox policies which focus on the total calorie consumption and not on food quality".

"The fat content on foods is not an indicator to estimate the long-term healthy positive and negative effects. Scientific evidence supports eating more calories from fruits, dried fruits, vegetal, whole grains, fish, yogurt, olive oils, etc. and less calories from processed products rich in starch, sugar, salt or trans-fat" says Mozaffarian. "We ignore this evidence including these results from the study of the Predimed prevention study - under our responsibility" concluded.