New Trial: LCHF vs "Medium Carb Low Fat". Who Wins?

[borofergie]

First let's get the negatives out of the way: this is a small trial (34 people randomised to two groups) and relatively short term (3 months). This is because it is a pilot trial, designed to test the efficacy of the intervention and the experimental method, as a 'proof-of-concept' for a bigger trial.

The randomized trial compared the effect of a "low-fat, calorie restricted diet in line with ADA guidelines" (40-50% carbohydrate by calories) against a "very low carbohydrate, high-fat, non-calorie controlled diet" (20-50g carbs per day).

It's quite unusual that we get to see a proper low-carb diet compared to the standard medium-carb / portion control diet.

Let's see which diet won:

A key finding of this randomized controlled trial was that a low carbohydrate diet was more effective than a standard, moderate carbohydrate diet at reducing HbA1c at three months, our primary outcome point. These results are consistent with those of several prior studies that have found substantial improvements in glycemic control with low carbohydrate diets in the setting of a metabolic ward or in controlled studies.

These results provide important support for the benefit of low carbohydrate diets in type 2 diabetes for glycemic control, as well as the feasibility of adhering to the diet for at least three months in a community setting.

In addition, the improvement in glycemic control was observed despite greater decreases in diabetes medications, particularly sulfonylureas in the low-carbohydrate group

The last point is quite important - the HbA1c improvements would probably have been even bigger if they had not weaned some of the low-carb group off their medication.

56% of patients in the low-carb group showed a clinically significant reduction in HbA1c, compared to only 22% in the medium-carb/portion control diet. Every single member of the low-carb group managed to drop their HbA1c to some extent.

It's also quite interesting that the medium-carb/portion control group spontaneously dropped their carb intake from 224 to 160g of carbs per day.

The low-carb diet also performed better in terms of weight loss, and in a measure of the mood of participants.

.

 

[borofergie]

Sorry, forgot to post a link to the actual study:
A Randomized Pilot Trial of a Moderate Carbohydrate Diet Compared to a Very Low Carbohydrate Diet in Overweight or Obese Individuals with Type 2 Diabetes Mellitus or Prediabetes

 

[Spiker]

Interesting. Definitely interesting that it was head to head with an ADA diet. One more 'but' to add to the list - by picking a measurement point of only 3 months out, the design of the experiment is pretty much ducking the question of long term adherence, which arguably matters more than almost any other factor (as long as the diet actually does have some actual benefit). If I was the ADA I would be claiming "yeah but", "yeah but people can actually maintain our diet as a life style change, whereas they will never sustain the VLC diet".

 

[borofergie]

Interesting. Definitely interesting that it was head to head with an ADA diet. One more 'but' to add to the list - by picking a measurement point of only 3 months out, the design of the experiment is pretty much ducking the question of long term adherence, which arguably matters more than almost any other factor (as long as the diet actually does have some actual benefit). If I was the ADA I would be claiming "yeah but", "yeah but people can actually maintain our diet as a life style change, whereas they will never sustain the VLC diet".

The 3 months duration was only because it was a pilot study. The full scale trial would be over a much longer time period.

 

[Spiker]

The 3 months duration was only because it was a pilot study. The full scale trial would be over a much longer time period.

Of course. It's very expensive to run longer term diet studies. I guess we will see next time. Or if there is a follow up study on the participants of this study maybe.

 

[borofergie]

If I was the ADA I would be claiming "yeah but", "yeah but people can actually maintain our diet as a life style change, whereas they will never sustain the VLC diet".

And I'd say to the ADA, "yes, but we do have definitive proof about what happens when you put T2 diabetics on a high-carbohydrate ADA style diet over a long period. No matter how many medications you give them, their diabetic control deteriorates and they suffer complications."

From the UKPDS trial (43% carbohydrate diet):

Even insulin won't save T2Ds from an ADA style diet.

 

[Spiker]

Sure but none of that matters. Even if all the ADA diet does is stave off slow lingering death, if the other diet can't be adhered to for more than 3 months, then the ADA diet still wins. Even if some wonder diet drops my HBA1c to 4.4%, it's no use if adherence is impossible.

I'm just making a devil's advocate argument here. In summary, a promising set of results but would now need to be proved in a longer term trial.

 

[Spiker]

Or to put it another way, the New Trial presents no evidence that suggests the VLC would do any better than the ADA diet over the timescales that are shown in your big graph. It's just a promising suggestion, not evidence, at this point.

 

[borofergie]

I agree, it is just a promising pilot trial, but that's all we have until someone funds a long term trial. I don't know about you, but I'm not prepared to wait for 10 years to see if low-carbing works, and suffer bleeding eyeballs, amputated toes and failing kidneys in the meantime.

 

[Spiker]

Hmm it's a bit poor that the medium carb group and low carb group had different diet educators. So are we testing for VLC vs ADA, or are we testing for course leader A vs course leader B's motivational skills. There is no way to tell. That's a bad experimental design. Disappointing.

 

[borofergie]

And of course there is some data that shows good adherence to Low-Carbohydrate diets, in this trial (for T1s) there was 50% adherence to 75g carbohydrate diet over 4 years:
http://www.dmsjournal.com/content/pdf/1758-5996-4-23.pdf

 

[Spiker]

I agree, it is just a promising pilot trial, but that's all we have until someone funds a long term trial. I don't know about you, but I'm not prepared to wait for 10 years to see if low-carbing works, and suffer bleeding eyeballs, amputated toes and failing kidneys in the meantime.

Yeah I'm happy to place a bet on low carb. Anyway for individuals, adherence isn't a risk. I either adhere to the diet or I don't. Adherence is only a risk for institutions or big organisations that are evaluating whether it's worth the effort of enrolling large numbers of people onto the diet. As an individual I can just decide that I like the results shown for 3 months on the VLC, and go for it, try as hard as I can, and if I can adhere to the diet past 3 months. all is rosy.

 

[borofergie]

Hmm it's a bit poor that the medium carb group and low carb group had different diet educators. So are we testing for VLC vs ADA, or are we testing for course leader A vs course leader B's motivational skills. There is no way to tell. That's a bad experimental design. Disappointing.

Come on, really? How do you think that would work on the scale of something like UKPDS? One person educates everyone? I don't think you can say that adherence to either diet was bad based on the data in the paper.

And in general, you need to test the efficacy of the dietary information, no the motivational skill of the course leader.

 

[borofergie]

Yeah I'm happy to place a bet on low carb. Anyway for individuals, adherence isn't a risk. I either adhere to the diet or I don't. Adherence is only a risk for institutions or big organisations that are evaluating whether it's worth the effort of enrolling large numbers of people onto the diet. As an individual I can just decide that I like the results shown for 3 months on the VLC, and go for it, try as hard as I can, and if I can adhere to the diet past 3 months. all is rosy.

Yes. Exactly.

Almost ALL of the data shows the superiority of carbohydrate restriction for short term glycemic control (I can think of only one study in which it was a draw). We know that a high-carbohydrate diet won't help you glycemic control (and will probably make it worse).

If I can show someone a way to get their HbA1c under control inside 3 months, and they aren't motivated enough to stick to it, then as far as I am concerned that's a personal choice, and my sympathy stops there.

 

[borofergie]

Although the problem with this is that your general T2D on the street never gets their hands on the information, or if they do their perception is so dented by the NHS advice (and prejudice against Akins) that they are never in a position to make the correct decision.

I've sat and watch @IanD describe the benefits of low-carb to a typical T2D audience (Hounslow diabetic group), and although they were receptive, most of them had never even heard of low-carbing as a method for controlling diabetes.

 

[Spiker]

Come on, really? How do you think that would work on the scale of something like UKPDS? One person educates everyone? I don't think you can say that adherence to either diet was bad based on the data in the paper.

And in general, you need to test the efficacy of the dietary information, no the motivational skill of the course leader.

Right, but this wasn't anything like on the scale of the UKPDS. This was two groups of 15 or 16 people, each with different diets and different motivational instructors. And motivation was part of the experimental design. Small groups of that size can easily be influenced by the quality of motivation and education. In my view this was careless experimental design. They should have randomised both diets across both educators, if they needed 2 educators. Sloppy and potentially wasted the money they put into the study.

 

[borofergie]

Right, but this wasn't anything like on the scale of the UKPDS. This was two groups of 15 or 16 people, each with different diets and different motivational instructors. And motivation was part of the experimental design. Small groups of that size can easily be influenced by the quality of motivation and education. In my view this was careless experimental design. They should have randomised both diets across both educators, if they needed 2 educators. Sloppy and potentially wasted the money they put into the study.

But how would that work when they do scale it up? The pilot study is supposed to be testing procedures that can be used in the bigger study, where having a single educator will likely be impossible.

 

[Spiker]

But how would that work when they do scale it up? The pilot study is supposed to be testing procedures that can be used in the bigger study, where having a single educator will likely be impossible.

When they scale it up, it won't matter because if they have fifty educators instead of two those fifty educators will be randomised over the 2 diets, so it will be very easy to demonstrate statistically that the causation is the diet and not the educator. But when you have 2 diets and 2 educators and assign all subjects on the same diet to the same educator, you have just torpedoed your experimental protocol. Every claim this article makes for the VLC diet over the ADA diet can be equally argued to be a claim for the abilities of instructor LC over instructor RS. There is literally no way to prove which of these hypotheses on causation is more valid. They are equally valid. As the instructors are also the authors, that means it's not a double blind trial, which casts further doubts. These guys have shot themselves in the foot by a poor design. If they had just run 4 classes and made sure each educator had taught both diets, they would have avoided this problem and actually also done a better job of validating a model that would scale up to a larger scale study. All I can say is "Doh". :-(

 

[LittleGreyCat]

I'm with Spiker on this one.

A potentially very useful trial compromised by some poor design decisions.

@borofergie - we know you have strong views on LCHF and many agree with you including myself - however this shouldn't influence the analysis of individual trials. A badly designed trial can actually have a detrimental effect on a valid proposal. Support for badly designed trials because you like the result can also undermine an otherwise strong position.

Please bear in mind the current issues with drugs such as statins where the drug companies only published trial data which supported their drugs and so there is now even less trust in anything they tell us.

A balanced view is always the strongest in the long term.

Cheers

LGC

 

[mo1905]

When they scale it up, it won't matter because if they have fifty educators instead of two those fifty educators will be randomised over the 2 diets, so it will be very easy to demonstrate statistically that the causation is the diet and not the educator. But when you have 2 diets and 2 educators and assign all subjects on the same diet to the same educator, you have just torpedoed your experimental protocol. Every claim this article makes for the VLC diet over the ADA diet can be equally argued to be a claim for the abilities of instructor LC over instructor RS. There is literally no way to prove which of these hypotheses on causation is more valid. They are equally valid. As the instructors are also the authors, that means it's not a double blind trial, which casts further doubts. These guys have shot themselves in the foot by a poor design. If they had just run 4 classes and made sure each educator had taught both diets, they would have avoided this problem and actually also done a better job of validating a model that would scale up to a larger scale study. All I can say is "Doh". :-(

Spiker makes some very good points here which I totally agree with and whether or not the results of this small scale study can be deemed valid or not is debatable, however, it's a step forward that at least studies like this are beginning to happen and some professionals are beginning to look at low carb advice very seriously.