Thursday, April 3, 2014

It's what you eat, not what you call the diet.

David Katz and Stephanie Meller co-authored a systematic (careful, organized, detailed) review of research related to 7 popular dietary patterns (e.g., low carbohydrate, low fat, Mediterranean, paleolithic, vegan).  You can access their work, including a table that lists the diet categories and the features of that diet here.  For example, the paleolithic diet is based on - or tries to emulate - what we believe our Stone Age ancestors ate, therefore people consuming a paleolithic diet avoid processed foods and eat a lot of vegetables and fruits. The rationale for why each diet pattern is included in the review, or why we should care, is also listed in the table.  For example the low glycemic diet is included because a lot of research is devoted to studying how the body handles foods of different glycemic values (I have blogged about this) and glycemic index and glycemic load could matter for diabetes control.

The actual research article is about 13 pages long.  It is thorough.  It is NOT hard to read - if you have ever asked yourself (or me!), "which is the better diet?" - take the time to read the article for yourself.  Heck, start with the discussion section at the end if you like and if intrigued, go back and read the information about the diets themselves. The authors do not throw statistics at you.  They tell you why they chose to include certain studies, for example, because they were experiments that included a representative sample.  We, the readers, take it on faith that the study authors' (Katz and Meller) interpretation is correct and that they have done due diligence.  I want you to know that I feel confident in the conclusions made by these two authors. 

Here is the take away.  With regard to weight, it is still about calories and some diet patterns make it easier for a person to consume the right amount of calories for themselves.  That is not universal; the pattern that is right for me might be a disaster for you.  If you're curious, I am a blend between Mediterranean and vegetarian as these diet patterns are described in the article.  [That is an important point.  Any of these diet patterns can be trouble if the substitution one makes is to a food containing a high amount of a nutrient of concern, e.g., stop eating cheeseburgers start eating cake.]

But Drs. Katz and Meller were writing about diet patterns and health not weight loss.  Is it healthier to avoid meat altogether or to eat a low carbohydrate diet, for example?  At the conclusion of their study of the studies, Katz and Meller emphasize that we already know the answer and no matter how we actively or passively distract ourselves with the 'diet of the day,' the truth is the same.  A plant based diet, which is minimally processed and contains select carbohydrates (my new favorite way of distinguishing them), and meats that when eaten come from animals who themselves had a natural, plant based diet is health promoting.  The review also debunks the myth that grains make you fat and instead supports a dietary pattern that includes whole grains which are high in fiber because they are associated with lower rates of disease and better weight control.  My Mediterranean diet is high in whole grains and fiber.

Just an FYI, another way that Katz and Meller address the oft misunderstood carbohydrate is to suggest limiting "the objectionable carbohydrate sources—namely, starches and added sugars."
Amen to that.

Here is the proper citation and a link to the article.
Katz, D. L., & Meller, S. (2014). Can We Say What Diet Is Best for Health?. Annual Review of Public Health, 35(1).

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