For healthy weight loss the real evidence backs the Mediterranean diet

    8 June 2016

    The current controversy between those challenging the dietary advice of the last 40 years and those who hide behind ‘expert opinion’ and ‘guidelines’ is an entertaining one to watch. The evidence seems overwhelmingly to support the contentions of the former.

    However, nutritional medicine does suffer from a lack of good evidence. The ‘gold standard’ of a randomised controlled trial (RCT) is often not available. This is because of the lack of financial potential of any results, and the fact that it takes more resources to run a trial and then follow up the participants for an appropriate amount of time than any official body is willing to fund.

    Enter the Mediterranean diet, which thankfully has been the subject of a number of RCTs and meta-analyses. The diet essentially emphasises healthy fats such as olive oil, nuts and seeds, fish and other natural protein sources, fresh fruit and vegetables and whole grains. Processed food is kept to a minimum as well as processed carbohydrates.

    A new RCT has been published, assessing the impact of a Mediterranean diet on fat loss in a high-risk population of obese and diabetic and obese individuals.

    The study followed 7,447 patients who had type-2 diabetes or three or more cardiovascular risk factors assigned to three interventions: Mediterranean diet supplemented with extra virgin olive oil (a litre per week); Mediterranean diet supplemented with nuts, or a control diet (which just involved advice to reduce dietary fat). There was no calorie counting involved, nor exercise. Patients were followed for five years.

    The observed results show how statistical significance does not always mean clinical usefulness. Patients consuming the most fat experienced the most statistically significant drops in waist circumference and weight, as compared to the low-fat group. However, a body weight difference of 0.4 kg or a waist circumference change of 0.94cm is hardly the profound difference the results seem to suggest.

    The study was done in a relatively uncontrolled setting; previous trials performed in a more controlled manner showed significantly more weight loss occurring. Perhaps the addition of exercise (a known insulin sensitiser) and intermittent fasting might have made a difference?

    I would suggest that anyone looking for evidence of the efficacy of the diet look to previous studies instead; this new research adds to our knowledge, but does not in isolation suggest that the diet is particularly helpful. (The Mediterranean diet has already been found to be superior to a low-fat diet for weight loss and maintenance. It has also shown to be preventative for people at risk of diabetes and effective at ensuring glycemic control in diabetics.)

    Weight loss is more than simple calorie counting and has to take hormones into account; the study subjects here all undoubtedly had evidence of systemic inflammation or insulin resistance, both of which are known to make weight loss even more arduous and which might explain the unspectacular results.

    The Mediterranean diet is an evidence-based diet that does not involve having to eat bland, low-fat food. It is sustainable, with an excellent track record in helping to decrease body fat, control blood sugar and contribute to overall health. If any diet is to be encouraged, it should be this one, not the scientifically dubious, epidemiologically disastrous and witch-doctor-based-medicine diet that is the ‘standard recommended diet’.