More on the latest LC/LF Diet Comparison Study, and Why LF & CRD's "fail"?

This post is a continuation of LC v. LF Diet Comparison Study Shows Calories Determine Weight Loss, discussing the following study:

In type 2 diabetes, randomisation to advice to follow a low-carbohydrate diet transiently improves glycaemic control compared with advice to follow a low-fat diet producing a similar weight loss

What distinguished this study from many other comparison studies, was that there was an attempt at keeping calories constant between the diets.  Usually LC is ad libitum, which, especially the first time one follows a low carb diet, tends to substantially spontaneously reduce caloric intake more than what is generally prescribed for a "responsible" calorie restricted diet (CRD).  This was also a longer term study where macro percentages were fixed for the duration of the trial (as opposed to the Atkins induction and progression to increase carbs in many trials).  Presuming compliance, then, the study controlled for calories and sought to look at the effects of just the macronutrient composition of the diet.  

In my opinion, the rather negligible differences for both groups after a year and continuing through two years show that neither dietary intervention was particularly effective, resulting in under 10 lbs weight loss and only transient improvements in HbA1c as measured by one method only.   So why was that?  Well, the prescribed caloric intake was fixed at 1600 cal/day for women and 1800 cal/day for the men.  Right there this part of the study design pretty much doomed it to failure.  While men generally have higher caloric needs than women, total daily energy expenditure varies so widely between individuals that clearly some women have higher needs than some men, and some men and women have higher needs than others of their gender.

When I read the study, I thought that the 1600/1800 cal/day was a bit high but didn't pay much attention to the kJ's:   1600 cal = 6,694 kJ , 1800 cal = 7,531 kJ.  I had looked at the caloric breakdown of the "diets" in the last post, but for some reason neglected to look at the breakdown of the baseline diets.  Let's take a look now.  Baseline diets -- based on 3 days logging for which the subjects were provided scales/measuring devices and included one weekend day.  
LF group = 7569  kJ = 1809 cal                LC group = 7071 kJ = 1690 cal
Hmmmmm ....  Perhaps the reason conventional advice "fails" for weight loss is because a caloric deficit is not even prescribed in many cases??   Ahh ... but maybe this wasn't really intended to be a weight loss study, rather a diabetes management one.  I think this excerpt from the intro indicates otherwise:  
Weight loss in obesity generally leads to improvement in cardiovascular risk factors and glycaemic control. However, few randomised studies have specifically targeted type 2 diabetes to compare the effect of different diets in this respect.
How is it nobody thought to alter the study protocol from the get-go based on the fact that the calorie prescriptions  were so darned close to maintenance calories for the participants?  Why not at least estimate the baseline caloric needs using a formula?  Even though these can over/underestimated for the individual (depending on the equation used and activity estimates) this is far better than using a fixed 1600 cal for all women, and 1800 cal for all men.
The size of the study was based on an earlier 6 month pilot study of 28 participants with type 2 diabetes who were randomised to the same diets as in the study presented in this paper. Twenty individuals completed the pilot study and both diet groups achieved similar weight reductions, while HbA1c levels tended to be lowered in the low-carbohydrate group only, without taking change in medication into account (low carbohydrate, p = 0.068; low-fat group, p = 0.8). Based on these results, the study sample was increased to at least 30 individuals in each group in the present study.
In my opinion, when calorie restriction is part of the intervention, efforts should be made to ensure the calorie deficit is as uniform as possible by measuring baseline needs in some fashion.   To repeat, any of the regression equations will be better than the 1600/1800 numbers, but two ways I've seen this implemented in better studies are:
  • 1-2 week lead-in period where usual intake is logged (or even better tightly monitored) to determine weight-stable intake.
  • Measuring REE and assigning a caloric intake on a %REE basis or estimating TDEE from REE and assigning a fixed deficit.   

This study did neither, it just assigned an arbitrary calorie level based on gender, and somehow didn't notice in either the pilot study or in the baseline dietary logs that these prescriptions were unlikely to produce weight loss.    So this study gives us a clue perhaps as to why "traditionally recommended [diet] for the treatment of type 2 diabetes in Sweden, with 30 E% from fat (less than 10 E% from saturated fat), 55–60 E% from carbohydrate and 10–15 E% from protein" apparently fails patients.  

I've augmented the intake data from the last post to include a column at right for the target prescription.  I used 1700 avg. cals as the target intake.  Note:  The n's are for those who completed the 3-day logs at each time point, at 24 months of the 14 non-reporters, 10 were LC and 4 LF.  I noticed a few things when I gave this table a second look.  First, they probably lost nominal weight because they didn't consume the target calories, although the authors acknowledge that under-reporting could be at play here.  

Next just scan across each of the macro lines for the LF diet -- they remain essentially unchanged!  IOW, the "prescribed" LFD is quite similar to how these people were eating to begin with.  Now one interpretation of this is that such a diet is what made these people fat and diabetic.   But another way to look at this is that the LF "intervention" was more of a "usual diet" control than an intervention.  The LF group fell far short of the goal to reduce protein and increase carbs, and supposedly were already eating a low fat diet.   I note also that in the LC group, baseline macros are more in line with the SAD (I have no idea what the SwedishD really breaks down to) surveys.  If that group had been assigned LF, then there would at least have been a nominal reduction in fat.  But I would also like to quibble with what constitutes a low fat diet.  Despite what certain science journalists would have you believe, the diet (to use an example of one population now at high risk for obesity and diabetes) eaten by those "sprightly" Pima was anything but LCHF:  "We estimated that the traditional Pima diet, although seasonably variable, was ∼ 70–80% carbohydrate, 8–12% fat, and 12–18% protein."  So what the Swedes, and most people for that matter, consider a low fat diet these days, is not really so.  

Did the LC group really eat a "high fat" diet?  Nope!  They did initially up their fat intake considerably from baseline (39% to 49%), however combined with decreased consumption this resulted in an average of only 2g fat/day more!  And by 24 months it was only 5% of calories more, and ... da, da, daaaah! ...  at 61g  almost a tablespoon of butter's worth less than the 73g/day at baseline.  

The more I look at this data, the bigger cluster you-know-what it all seems to shake out to be.  Neither group altered their protein consumption much to comply with the prescribed diet guidelines.  The LF group in particular actually increased protein slightly when it should have been cut, and while the LC group increased it a bit more, they fall far short of the 30% target.  All-in-all, compliance seems extremely poor here, yet I see no real mention of that in the discussion.  They did a separate "completers" analysis for those who complied with the target fat percentages defined as 35% for LF (n=20) and 45% for LC (n=12).    Check out those n's!  Only roughly 1/3rd of the "high fat" group actually ate the prescribed diet.  The rest, as they say, actually ate a lower fat (in absolute amounts) diet.

Given as medications were continued (and even initiated as was the case for statins in some) during the course of the study, and given that dietary compliance was so poor as to virtually nullify any difference in the intervention diets, this study seems pretty useless in providing ANY meaningful comparisons.  

The main outcome touted in the title -- the glucose levels -- is, as the title says "transient".  

In comments here and elsewhere the usual "it's not a proper LCHF diet" and "imagine how much better the outcome would be with keto diet" responses have been made.  That's all fine and good, but then this study should not be touted as how a high fat diet -- in the 70+% range touted by most advocates -- is effective in treatment of diabetes.  It may well be an alternative that produces nominally better short term results than a not-very-LF diet.  And both were equally relative failures for weight loss and long term diabetes management.    To the "what if it was proper keto?" I suggest:  Diabetes "Crash" Cures: VLCal vs. VLCarb as it discusses the Westman study referenced by this paper.  The Israeli Shai study that Taubes loves to do a mangled analysis of is also cited:  
Interestingly, in a randomised 2 year study from Israel that achieved good compliance, a high-fat diet was shown to induce better weight reduction and improved blood lipid levels than a traditional LFD in obese participants, while the subgroup of patients with diabetes who were randomised to the high-fat diet exhibited the largest reduction in HbA1c levels.
I'm not sure I'd describe Shai as demonstrating good compliance, and again, I get rather tired of the HF v. LF comparisons gleaned from that data when there was a third dietary intervention that goes ignored:  the highest carb Mediterranean diet!  I've discussed this here: Gary Taube$, Shai-ster  (yep, $ sign and play on words and all).  The LF diet in Shai was similar to this current study -- aim of 30% -- but calories were a bit lower (1500F/1800M).  The LC (HF) diet was Atkins induction then climbing the rungs aiming for 120g/day max.  In the end (2yrs), the "high fat" dieters in Shai reported eating slightly fewer fat grams than at baseline, as their fat intake as a percent only increased from 32% to 39% (and carbs were only reduced from 51% to 40%).   Yes, the "low carbers" did have the largest reduction in HbA1c:  "Among the participants with diabetes, the proportion of glycated hemoglobin at 24 months decreased by 0.4±1.3% in the low-fat group, 0.5±1.1% in the Mediterranean-diet group, and 0.9±0.8% in the low-carbohydrate group."  While the reduction in the LC group was the only statistically significant change vs. baseline, it was not reported whether the differences between groups were significant.  Given the small numbers of subjects in this subset and the large SD's, I doubt there was a statistically significant difference.  In any case, I wonder why the authors ignored the other outcomes in Shai for the diabetics, blogged on here:

Red = LF, Orange = MDTN, Blue = LC

The T2's did best on the Mediterranean diet at the two year mark on the markers of insulin resistance.  

Ultimately these studies tend to raise more questions than they answer.  I would love it if individual result scatter plots were provided in addition to means and such, and I think for long term studies such as Shai and this current one more diligence should be paid to assessing intake -- either more frequently, over the course of more days to average, or both.  This study shouldn't be added to any list demonstrating the glories of LCHF diets for treating diabetes with diet only.  I'm not saying that LCHF is not a viable intervention, heck, some version of LC is probably the best acute short term intervention, but these sorts of studies do not provide evidence to support the advocacy of 70+% fat diets over the long run.   But no doubt this will be added to the lists anyway.

I can't help but wonder if the researchers that designed this study did so to have LF "fail" ... inadvertantly they ended up showing that LC pretty much failed too. 


James Krieger said…
I'd like to note that the self reported 1809 and 1690 calorie intakes are likely not the true maintenance intakes of these individuals. Underreporting in these populations tends to be quite prevalent, and there are studies showing that if you actually provide an overweight/obese person with this amount of calories, they lose weight. Thus, the prescription is likely not nearly as close to maintenance as it might appear at face value.
julianne said…
This comment bothers me "The body absorbs the fat it needs and excretes the excess." From an article in the Daily Mail by Zoe Harcombe.

Read more:

As a nutritionist - I can't understand why so many low carb guru's keep saying things that are biologically wrong. Excrete fat if you dont need it - when I learned nutritional biochemistry fat was the most easily stored macronutrient - as body fat.
Sue said…
I don't think the body sits there and says okay my stores are full of fat so I will send a message to bile and lipase to take a holiday today and let the fat eaten go straight through and down the toilet!! You could just eat a lot of fat at one sitting and some of it escape digestion/breakdown by enzymes.
Nigel Kinbrum said…
Fat leaving the GI tract unabsorbed is fairly obvious. Just ask anybody who uses a lipase inhibitor. Steatorrhea a.k.a. "the soily oilies" is horrible!

Large amounts of dietary calcium caseinate can bind to dietary fat to form calcium "soaps". That increases the amount of fat excreted, but the amount isn't huge (~10g/day).
CarbSane said…
I agree James, it's probably likely ... and likely reporting was underestimated all along the way. That 24 month data looks quite off, as did Shai's befor.
CarbSane said…
^^ OK, that Testing was because I had a long comment to Julianne here earlier and it got eaten :(

Zoe Harcombe has been on my radar for quite a while. Since she doesn't seem to have a huge following or much influence -- despite her goal to cure the obesity epidemic starting in the UK -- I've not addressed her much here of late.

That quote is a perfect example of scientific mythology that bothers me. Can't say I haven't heard that theory before on Jimmy's forum, sadly. But going on that theory, she also rants against 5 a day but says carrots should be eaten with lashings of butter so that the vitamin A is absorbed. Well, if that statement is true, doesn't the fat dissolve the "A" and send it out? Somehow this woman is an "obesity expert"?

Hopefully we won't be hearing her on Ask the Low Carb Experts, though I fear eventually we will.
CarbSane said…
To add, fat absorption is pretty high absent some serious condition. I recall in one study they overfed up to 600g cream (oil, butter, cream, rendered fat, all highly bioavailable) and the absorption was in the high 90's (want to say 97%).

Not absorbing fat in excess of daily needs wouldn't seem to be very advantageous!
Sanjeev said…
James - you, Lyle & Alan should get off this "erroneous self reporting" schtick.

But I suppose as long as you insist on being true to the lit I can't offer a reasonable alternative ...
Sue said…
Kind of on a different subject, have you heard of duodenal switch. I was reading how someone eats 4000 calories but only absorbs a third of calories due to this weight loss surgery.
CarbSane said…
Thanks Nigel, that's the one!
CarbSane said…
Haven't heard about that one. I suppose if someone needs to eat a lot, it would be an option. I can't imagine 2/3rds passing through to be too comfortable though ;)