Tuesday, February 25, 2014

Saturated Fat Makes You Fat! You Read the Press Release - Here is the Whole Story: A Story of Muffins, SFA, MUFA, PUFA, Body, Liver & Visceral Fat and N6s & Lean Mass

I have to admit: Whether a conclusion as general at this is warranted based on the data from a recent study is questionable.
Somehow I knew that people would freak out, about a press release I reposted on the SuppVersity Facebook page earlier today (read it!). Next to saying that you can eat fructose and not get obese saying that you can eat PUFAs without getting fat is probably as heretic as saying that saturated fat makes you fat... what? Oh yes! You're right, it can be even worse. I mean, imagine you'd say that unsaturated fatty acids are less obesogenic than saturated fats.

Ah, come on! That's so mainstream it must be propaganda from the "pharmaceutical enteprise/ cholesterol lowering drug entreprise" [sic!], right?

Well, I am just looking at the acknowledgements of the study the press release refers. Let's see: "None of the authors have any conflicts of interest to disclose" and "This study was funded by the Swedish Research Council (project K2012-55X-22081-01-3)." No, I wouldn't say this sounds like there had been a "pharmaceutical enteprise/ cholesterol lowering drug entreprise" funding the study
Just as an aside: Discarding the results, because the results are not inline with your own indoctrictinat like the guys who sponsored it, is pretty pathetic. If you want to argue that the results Fredrik Rosqvist and his colleagues from the Uppsala University, and the Center for Clinical Research Dalarna are b*s*, you better take a look at the study design to identify flaws and shortcomings - and guess what?! That's what we are about to do now.
Now that we have all calmed down a bit, let's see what exactly we could freak out about - or, to put it differently, let's take a closer look at the study design, the results, and their interpretation.

I - The Research Question

I know that many of you don't care about questions. That's a mistake. In science, questions are everything. Answers are secondary. The motto of a true researcher is thus - just as the Greek philosopher Euripides had it -  "Question everything. Learn something. Answer nothing." In the end, we've already made a very good start by questioning the scientists' conclusion that
"[...] overeating SFA promotes hepatic and visceral fat storage whereas excess energy from PUFA may instead promote lean tissue in healthy humans." (Rosqvist. 2014)
What we are interested in part I of our analysis are not our questions, though. What we want to look at now, is the question that worried the researchers, the questions, whether ...
"[...]liver fat accumulation during moderate weight gain could be counteracted if the excess energy originate mainly from PUFA rather than from SFA." (Rosquist. 2014)
This question, as logical as it may seem for the average individual who has been sucking up the "good fat (PUFA) vs. bad fat (SFA)" mantra with his PUFA-enriched formula ever since he was born, is obvious a reason to freak out for the meanwhile almost as average black-and-white thinking inhabitant of the blogosphere.

Don't interpret this article as incentive to follow all dietary recommendations to the "T" before you've read my 2012 article on the effects of an allegedly heart healthy low fat diet on the LDL particle profile of healthy volunteers | read more
What this question is not, though, is pure invention. The idea to investigate whether liver fat accumulation during moderate weight gain could be counteracted if the excess energy originate mainly from PUFA rather than from SFA was born, when the researchers observed an isocaloric diet rich in PUFA given for 10 weeks reduced liver fat content and tended to reduce insulin resistance compared with a diet rich in SFA in individuals with abdominal obesity and type 2 diabetes (Bjermo. 2012) - the differences were not earth-shattering, but statistically significant (-1% total fat in PUFA vs, +0.6% body fat in SFA); and the "improvements" in the visceral fat to subcutaneous fat ratio (a marker of a healthier fat distribution) in the PUFA group of the Bjermo study were brought about (mainly) by increases in subcutaneous body fat in the PUFA group.

In view of the fact that the alleged improvements (in many cases the values simply worsened less) of the blood lipids, glucose and insulin levels, the hypothesis that "liver fat accumulation during moderate weight gain could be counteracted if the excess energy originate mainly from PUFA rather than from SFA" (Rosquist. 2014) is legitimate, but probably optimistic.

II - Study Design

So, if the underlying hypothesis is valid, the next thing we could target to debunk the claim that saturated fats are more fattening / unhealthier than unsaturated fats would be to have a closer look at the design of the LIPOGAIN study:
  • Figure 1: Rel. changes in liver, visceral and subcutaneous fat in subjects over-consuming a high vs. low (white) saturated fat diet.
    the subjects were randomly allocated to the two intervention groups
  • the scientists made sure that the subjects gained weight at identical rates (3%) (the amount of muffins consumed per day was individually adjusted weekly, i.e. altered by +/- 1 muffin/day depending on the rate of weight gain of the individual)
  • the dietary intervention was based on highly standardized food items 
  • muffins containing sunflower oil (high in the major dietary PUFA, linoleic acid, 18:2 n-6) or 
  • muffins containing palm oil (high in the major SFA, palmitic acid, 16:0). 
  • the muffing were baked in large batches under standardized conditions in a metabolic
    kitchen at Uppsala University
  • except  for  the type of fat, the  muffins  were  identical  with  regard  to  energy,  fat (51%),  protein (5%), carbohydrate (44%; sugar to starch ratio 55:45), and cholesterol content, as well as taste and structure.
I guess you will agree that there are no major design flaws, here. If anything, you could speculate that the changes in SFA and PUFA intake (-1.6% and +4.9% SFA intake and +7.9% and +0.3% PUFA intake in the PUFA and SFA group, respectively) were pretty pathetic and insufficient to produce significant results.
Figure 2: Relative contribution of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids to the total energy intake of the subject before and after the study (Rosquist. 2014)
If you take a look at my plot of these differences (you should be aware that they are expressed in terms of the total energy intake), you will have to concede, though, that the difference between SFA/PUFA ratios, i.e. 0.9 and 3.6, is pretty significant.
Figure 3: There is a distinct correlation between the relative amount of omega-6 fatty acids in the blood and the change in lean mass - a beneficial one!
More or less flawless, but still questionable: Whether that's enough for you to accept that the Rosquist et al. used their results to make a general statements about the effects of saturated vs. unsaturated fat intake is up to you. The same goes for the real-world significance of the different body and liver fat trajectories in Figure 1.

In view of non-negligible increases in total, liver and visceral body fat and the absence of the often-touted pro-anabolic effects of saturated fats (mind the proportionality of an increase in the allegedly bad omega-6 concentration in the blood and the lean mass increases / decreases in Figure 3), it's difficult to keep nibbling on a chunk of bacon without at least taking into consideration that the "bad PUFAs" may not be as bad after all.

"Whut?" Calm down, I am not suggesting that you have to go back to the "saturated fat is bad for you" mantra, but I would like to invite you to take a parting look at Figure 2 (right) and note that the main characteristic of the "PUFA" diet is not its high PUFA content, but it's balanced fat content. Maybe the sentence "The optimal diet is characterized by a balanced intake of all three main types of dietary fat" would thus be a conclusion we can agree on - ha?
  • Bjermo, Helena, et al. "Effects of n− 6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: a randomized controlled trial." The American journal of clinical nutrition 95.5 (2012): 1003-1012.
  • Rosqvist, Fredrik, et al. "Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans." Diabetes (2014): DB_131622.