Eating a non-calorie restricted Mediterranean diet high in vegetable fats such as olive oil or nuts does not lead to significant weight gain compared to a low-fat diet, according to a study published in The Lancet Diabetes & Endocrinology journal.
The study suggests that current health guidelines that recommend a low-fat, low-calorie diet create unnecessary fear of healthy fats present in a Mediterranean diet, which have known health benefits.
More and more scientific evidence suggests that total fat content is not a useful measure of harms or benefits of food, and that fats from nuts, fish and phenolic-rich vegetable oils are healthier than fats from meat and processed foods.
The study took place in 11 hospitals in Spain during 2003-2010 and included 7447 participants (men and women) aged 55-80.
They were randomly assigned to one of three groups — an unrestricted-calorie Mediterranean diet rich in olive oil (2543), an unrestricted-calorie Mediterranean diet rich in nuts (2454), or a low-fat diet where the advice was to avoid all dietary fat (2450).
All participants were at high cardiovascular risk or had type 2 diabetes, and more than 90% were overweight or obese.
After 5 years, total fat intake had decreased in the low-fat diet group (from 40% to 37.4%) and had slightly increased in both Mediterranean diet groups (40% to 41.8% in olive oil; 40.4% to 42.2% in nuts).
The percentage of energy intake from protein and carbohydrate decreased in both Mediterranean diet groups.
On average, participants in all three groups lost some weight with the greatest weight loss seen in the Mediterranean diet with olive oil group (0.88 kg weight reduction in the olive oil group, compared to 0.60 kg for the low-fat diet group and 0.40 kg for the nuts group).
There was an increase in waist circumference in all three groups with the greatest increase seen in the low-fat diet group (1.2 cm increase for the low-fat diet group, compared to 0.85 cm for the olive oil group and 0.37 cm for the nuts group).
One researcher says: “Ironically, just as focusing on total fat to prevent heart disease was misguided because it overlooked the different effects of specific fatty acids.”
“Dietary guidelines should be revised to lay to rest the outdated, arbitrary limits on total fat consumption.”
“Calorie-obsessed caveats and warnings about healthier, higher-fat choices such as nuts, phenolic-rich vegetable oils, yoghurt, and even perhaps cheese, should also be dropped.”
News source: Estruch R, et al. (2010). Effect of a high-fat Mediterranean diet on bodyweight and waist circumference: a prespecified secondary outcomes analysis of the PREDIMED randomised controlled trial. The Lancet Diabetes & Endocrinology, DOI: 10.1016/S2213-8587(16)30085-7.
