While I don’t believe that what represents an ideal diet is the same for everyone, I do favour diets that are generally rich in protein and relatively low in carbohydrate/ And one reason for this concerns that fact that such diets do tend to outperform high-carb, low-fat diets when it comes to fat loss and in blood markers of disease including certain blood fat levels.
A recent example of this came from a study in which individuals were randomised to eat either a higher protein, lower carb diet or a lower protein, higher carb diet over a year [1]. The former diet contained 1.6 g of protein per kg of body weight and less than 170 grams of carbohydrate a day, while the latter contained 0.8 g of protein per kg of body weight and more than 220 g of carbohydrate per day. The first four months was designed to provide individuals with a calorie deficit of 500 calories a day, and for the following 8 months the calorie intake was designed for weight maintenance (rather than loss).
At the end of the year, while weight loss was not significantly between the two groups, fat loss was: those on the higher protein diet did better on this measure. As a result this group had improved body composition (more lean body mass and less fat) compared to those eating the lower-protein, higher carb diet. And finally, they also did better on certain blood parameters, including low levels of ‘unhealthy’ blood fats known as triglycerides and higher levels of ‘healthy’ HDL (high density lipoprotein) cholesterol.
This study is accompanied by a podcast in which the lead author of this study, Dr Donald Layman, in which he is interviewed about this study and higher protein, lower-carb diets in general. You can listen to the podcast <a href=”http://www.nutrition.org/media/publications/podcasts/podcastLaymanfinal.mp3″>here</a>.
In the podcast, Dr Layman reiterates the point that higher protein diets do, overall, lead to better outcomes, particularly in terms of body composition. But he also raises another interesting point, in that his belief is that the effectiveness of any diet can only really be judged in individuals who actually comply with that diet. He explicitly warns against judging diets on data that comes individuals who didn’t follow the rules. When talking about this, he seems to refer specifically to a recent high-profile study that I wrote about <a href=”http://www.drbriffa.com/blog/2009/03/04/when-testing-the-effects-of-different-diets-it-helps-to-ensure-that-the-diets-are-truly-different/”>here</a>, in which individuals on ‘different’ diets actually ended up eating very similar diets. The point I made in this blog is that when testing the effects of different diets, it really does helps to ensure that the diets are genuinely different.
Dr Layman is also asked about the supposed link between higher protein diets and increased risk of cancer. He quite rightly, I think, warns that we should not infer causality from the epidemiological evidence. He makes the point too that in these studies, individuals tend to have had, in addition to higher protein intakes, lower intakes of fruit and vegetables and higher intakes of processed carbohydrates. I think the podcast is well worth a listen. To my mind it is an example of a scientist taking an eminently balanced and objective approach to the science. This is something I feel we could with a bit more of.
<strong>References:</strong>
1. Layman DK, et al. A Moderate-Protein Diet Produces Sustained Weight Loss and Long-Term Changes in Body Composition and Blood Lipids in Obese Adults Journal of Nutrition. 2009 139: 514-521