Could consumption of olive oil help protect against obesity?

I’m currently in Portugal, and practically all of my main meals have come in the form of meat or fish plus salad. The salads have come dressed with olive oil, and I’ve noticed here this is used quite sparingly. Part of the reason for that is that there is a common perception here that olive oil is fattening. On the other hand, the fat conscious Portuguese (well the ones I spend time with, anyway) will happily eat mounds of starchy carb. For instance, bread accompanies every meal, irrespective if that meal is loaded with rice or potatoes.

These same people think it’s odd that when I prepare a salad, I use very generous amounts of olive oil to dress it. What they also think is odd, from what I can gather, is how I can eat salads swimming in oil twice a day and not be overweight.

I thought about this when I came across a recent Spanish study that looked at the relationship between oil consumption and risk of obesity [1]. Basically, this study found that the consumption of olive oil (rich in monounsaturated fat) or a mixture of oils (including olive oil) were at significantly reduced risk of becoming obese over time compared to those consuming predominantly sunflower oil (rich in omega-6 polyunsaturated fats). Even though this study controlled for so-called confounding factors such as caloric intake and age, an epidemiological study of this nature cannot tell us whether or not olive oil somehow helps protect against obesity and/or if omega-6 fats somehow help cause it.

To answer this question, we would require long terms studies in which individuals are fed these different fats in controlled conditions for relatively long periods of time. I’m not aware that such studies have been done. However, there is an interesting study in monkeys. In this study, two groups of monkeys were fed different diets for 6 years. One group of monkeys was fed a diet which contained 8 per cent of calories in the form of trans fat (usually industrially produced fats). The other group of monkeys ate a diet enriched with monounsaturated fat. In both diets, 35 per cent of calories came from fat. Both groups were fed the same number of calories too.

At the end of the study, monkeys fed trans fat gained more than 7 per cent in body weight, compared to less than 2 per cent of the monkeys fed monounsaturated fat. Also, the trans fat-fed monkeys tended to accumulate their weight in an around the abdomen ” precisely the form of excess weight most strongly linked with conditions such as heart disease and diabetes.

This study provides at least some evidence that consuming olive oil might help afford some protection from obesity. It also provides good evidence that when it comes to weight and obesity, a calorie is not a calorie.


1. Soriguer F, et al. Incidence of obesity is lower in persons who consume olive oil. Eur J Clin Nutr 2009 Jul 22. [Epub ahead of print]

2. Kavanagh K, et al. Trans fat diet induces abdominal obesity and changes in insulin sensitivity in monkeys. Obesity 2007;15(7):1675-84.

6 Responses to Could consumption of olive oil help protect against obesity?

  1. Chris 24 August 2009 at 11:38 pm #

    In the seventies and eighties there was big weight pushing so called ‘benefits’ of polyunsaturated fat and including the proposition that the degree of ‘unsaturation’ could be beneficial to weight management.
    I cannot reference this but I recall circa the late eighties news reaching the likes of me that polyunsaturates did not live up to the promise and that instead mono-saturates fitted the bill. This is in agreement with your post.

    I have read proponents of the proposition that the super-availability of polyunsaturates and the concurrent super-availability of omega-6 EFAs in the western diet is the major food-health scandal and travesty of the age.

    On two levels I can support the merits of your post.
    In the last six – eight months I have really addressed the likely overabundance of n6 EFAs in my diet while making attempts to raise consumption and quality of mono-saturated fat and n3 EFAs. I feel remarkably better.
    Also Barry Sears, he of the ‘Zone’ series of diet and health books is a big advocate of olive oil.

    Between ‘The True You Diet’ and ‘The 7 day Zone diet’ I was provoked into considerable thought on dietary matters and with a radical departure from the (mainstream) misconceptions still prevailing in the ‘noughties’.

    Have a pleasant stay in Portugal – fancy trading places?

  2. The other (non-dietician)Kate 25 August 2009 at 10:19 am #

    Hi Dr Briffa,
    Is this south or north Portugal?
    In the north, which is close to where I live in Galicia, lard is also consumed along with olive oil. The pig is an important resource!
    I have found Portugese olive oil to be the nicest (and cheapest) olive oil and so may have a trip over the border to buy some.
    It is very hard to resist the bread – especially the wood-fired oven baked bread, but I stick to a once a week treat.
    Saludos from Galicia

  3. Dr John Briffa 26 August 2009 at 8:23 pm #


    South – but I know the north quite well and its local cuisine. You’re comments about the pig extend to Portugal: even as a committed carnivore I did not realise it was possible to consume so many parts of this animal. I’ll spare readers the details…

  4. Cal Orey 26 August 2009 at 10:05 pm #

    This shouldn’t be a question, it’s an answer. As the author of The Healing Powers of Olive Oil–I know that olive oil helps to keep obesity and its linked diseases at bay. Studies, anecdotes, and personal experience show it. I’m size 4, 120ish lbs., at 5’5″ — 56. Yeah, it works.

  5. Trinkwasser 11 September 2009 at 4:58 pm #

    “To answer this question, we would require long terms studies in which individuals are fed these different fats in controlled conditions for relatively long periods of time. I’m not aware that such studies have been done.”

    Er, it’s being done as we speak, on the entire population of the Western World. (grins cynically)

    Stephan at Whole Health Source

    is one place to find a bunch of useful information, also Peter’s Hyperlipid

    I’m also a fan of olive oil, the more peppery the better for the polyphenol/antioxidant content, probably one factor in the “Mediterranean Diet” which it appears the Mediterraneans are also now being talked out of following. Perversely (or not) that lard is probably also beneficial, I’m not alone in finding radical improvements to my lipids from replacing Omega 6s with saturated fat alongside the monounsaturates and Omega 3s.

    OK, that’s today sorted then, I’ll walk very fast to the butcher’s and come back with a rump steak which I’ll fry in olive oil and black pepper and eat with a salad (more olive oil) and wash down with some red wine and coffee (but not decaff!) and follow with a few strawberries and a square of 85% chocolate. See, I’m listening!


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