Author Topic: LCHF and healthy eating  (Read 162369 times)

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Offline Physicity

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Re: LCHF and healthy eating
« Reply #630 on: June 03, 2018, 04:12:05 PM »
The study you quote says 'may produce clinical improvements'.  This isn't evidence to support LCHF diets over standard of care for T2D, it is evidence that the study has not demonstrated that LCHF diets are worse than standard of care.  These are two different things.  It's like publishing a study on ghosts after investigating 100 haunted houses, not finding any ghosts, and concluding that ghosts may be real.  Yes they may be, but there is no evidence presented in the study to say that they are real, nor has the study provided evidence that they aren't real (only that the study did not find any in their sample).

The results, upon which the conclusions were based:
Quote
Results
Eighteen studies (n = 2204) were eligible for inclusion within the systematic review. The definition of a low-carbohydrate diet varied. At trial end, the descriptive analysis suggested that the low-carbohydrate intervention arm (LCIA) may promote favourable outcomes in terms of HbA1c, triglycerides and HDL cholesterol. The LCIA demonstrated reduced requirements for diabetes medication, which may have reduced the observed benefit of dietary carbohydrate restriction on HbA1c. Seven studies provided data to be included in the meta-analyses at 1 year. The meta-analyses showed statistical significance in favour of the LCIA for HbA1c (estimated effect = −0.28%, 95% CI −0.53 to −0.02, p = 0.03; χ 2 = 13.15, df = 6, p = 0.03; I 2 = 54%), HDL cholesterol (estimated effect = 0.06 mmol/L, 95% CI 0.04–0.09, p < 0.00001; χ 2 = 6.05, df = 6, p = 0.42; I 2 = 1%), triglycerides (estimated effect = −0.24 mmol/L, 95% CI −0.35 to −0.13, p < 0.0001; χ 2 = 1.88, df = 6, p = 0.93; I 2 = 0%) and systolic blood pressure (estimated effect = −2.74 mmHg, 95% CI −5.27 to −0.20, p = 0.03; χ 2 = 10.54, df = 6, p = 0.10; I 2 = 43%). Meta-analyses for weight, total cholesterol, LDL cholesterol and diastolic blood pressure did not demonstrate a statistically significant difference between interventions.

Well you're correct that the study does not show LCHF worse than the standard of care. But it's not all like your ghosts analogy. The study provides evidence, but the researchers have reservations about certain aspects, but these do not contradict the results.

(BTW, the reduced requirement for diabetes medication is huge. T2D is considered a progressive disease and standard of care rarely, if ever, results in reducing requirements for medication. Usually is the opposite over time.)

With results like 'estimated effect = −0.28%, 95% CI −0.53 to −0.02,', 'estimated effect = −2.74 mmHg, 95% CI −5.27 to −0.20, p = 0.03' , the effects are small indeed.   One P value is p=0.93!

This paper isn't doing much to promote LCHF.  But just so you know, I do believe this kind of diet is hugely beneficial, particulary for type 2 diabetes.  It's just that this paper isn't doing much to support that belief.

Offline RubyDuckman

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Re: LCHF and healthy eating
« Reply #631 on: June 03, 2018, 04:17:20 PM »
Okay, fine, it is evidence, but of very low quality.

Just like finding a new exoplanet is low-quality evidence of alien life.

That's a poor analogy. I would say comparatively this is of higher quality evidence than that.

This is direct measurements of effect with some categories showing evidence of a good probability, that is indirect finding.
Barely reaching statistical significance isn't even remotely the same as "good probability"


I think the HDL and Triglycerides findings showed good probability.
That's because you have no idea how statistics work.

Statistical significance isn't the same as clinical significance.

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Online John Albert

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Re: LCHF and healthy eating
« Reply #632 on: June 03, 2018, 04:51:04 PM »
Why wait until it is complete, unless you want to change the methodology to suit a particular result - which is unscientific, but it is what we are taught to do.

Be careful about projecting the inadequacies of your field onto the rest of science.

You'd do well to heed your own advice.

Huh?  Care to explain?

Correct me if I'm wrong, but you appear to apply principles of subjective statistics to scientific questions.

Can a single, unreplicated study from untrustworthy sources working outside their field of expertise represent objective evidence?

Offline CarbShark

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Re: LCHF and healthy eating
« Reply #633 on: June 03, 2018, 04:52:08 PM »
The study you quote says 'may produce clinical improvements'.  This isn't evidence to support LCHF diets over standard of care for T2D, it is evidence that the study has not demonstrated that LCHF diets are worse than standard of care.  These are two different things.  It's like publishing a study on ghosts after investigating 100 haunted houses, not finding any ghosts, and concluding that ghosts may be real.  Yes they may be, but there is no evidence presented in the study to say that they are real, nor has the study provided evidence that they aren't real (only that the study did not find any in their sample).

The results, upon which the conclusions were based:
Quote
Results
Eighteen studies (n = 2204) were eligible for inclusion within the systematic review. The definition of a low-carbohydrate diet varied. At trial end, the descriptive analysis suggested that the low-carbohydrate intervention arm (LCIA) may promote favourable outcomes in terms of HbA1c, triglycerides and HDL cholesterol. The LCIA demonstrated reduced requirements for diabetes medication, which may have reduced the observed benefit of dietary carbohydrate restriction on HbA1c. Seven studies provided data to be included in the meta-analyses at 1 year. The meta-analyses showed statistical significance in favour of the LCIA for HbA1c (estimated effect = −0.28%, 95% CI −0.53 to −0.02, p = 0.03; χ 2 = 13.15, df = 6, p = 0.03; I 2 = 54%), HDL cholesterol (estimated effect = 0.06 mmol/L, 95% CI 0.04–0.09, p < 0.00001; χ 2 = 6.05, df = 6, p = 0.42; I 2 = 1%), triglycerides (estimated effect = −0.24 mmol/L, 95% CI −0.35 to −0.13, p < 0.0001; χ 2 = 1.88, df = 6, p = 0.93; I 2 = 0%) and systolic blood pressure (estimated effect = −2.74 mmHg, 95% CI −5.27 to −0.20, p = 0.03; χ 2 = 10.54, df = 6, p = 0.10; I 2 = 43%). Meta-analyses for weight, total cholesterol, LDL cholesterol and diastolic blood pressure did not demonstrate a statistically significant difference between interventions.

Well you're correct that the study does not show LCHF worse than the standard of care. But it's not all like your ghosts analogy. The study provides evidence, but the researchers have reservations about certain aspects, but these do not contradict the results.

(BTW, the reduced requirement for diabetes medication is huge. T2D is considered a progressive disease and standard of care rarely, if ever, results in reducing requirements for medication. Usually is the opposite over time.)

With results like 'estimated effect = −0.28%, 95% CI −0.53 to −0.02,', 'estimated effect = −2.74 mmHg, 95% CI −5.27 to −0.20, p = 0.03' , the effects are small indeed.   One P value is p=0.93!

This paper isn't doing much to promote LCHF.  But just so you know, I do believe this kind of diet is hugely beneficial, particulary for type 2 diabetes.  It's just that this paper isn't doing much to support that belief.

Well, it wasn't intended as a promotion for LCHF and no one said it did promote LCHF diet for T2D. It is more evidence supporting LCHF diets over the standard care diet for Type 2 Diabetes.

FWIW, as I said before, reducing medications needed for T2D is a pretty big deal. That's by itself is worth the price of admission.

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I'm not a doctor, I'm just someone who has done a ton of research into diet and nutrition.

Offline gmalivuk

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Re: LCHF and healthy eating
« Reply #634 on: June 03, 2018, 05:30:04 PM »
Okay, fine, it is evidence, but of very low quality.

Just like finding a new exoplanet is low-quality evidence of alien life.

That's a poor analogy. I would say comparatively this is of higher quality evidence than that.

This is direct measurements of effect with some categories showing evidence of a good probability, that is indirect finding.
Barely reaching statistical significance isn't even remotely the same as "good probability"


I think the HDL and Triglycerides findings showed good probability.
Good probability of a tiny effect size is not really anything too exciting, though.
The world is so exquisite with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories for which there's little good evidence. Far better...is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides.

Online John Albert

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Re: LCHF and healthy eating
« Reply #635 on: June 03, 2018, 05:37:43 PM »
Well, it wasn't intended as a promotion for LCHF and no one said it did promote LCHF diet for T2D. It is more evidence supporting LCHF diets over the standard care diet for Type 2 Diabetes.

FWIW, as I said before, reducing medications needed for T2D is a pretty big deal. That's by itself is worth the price of admission.

It has nothing to do with LCHF diets in specific. It was a study of low- and moderate- carbohydrate diets. The term "LCHF" was not even mentioned in the study.

Offline CarbShark

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Re: LCHF and healthy eating
« Reply #636 on: June 03, 2018, 07:04:31 PM »
Okay, fine, it is evidence, but of very low quality.

Just like finding a new exoplanet is low-quality evidence of alien life.

That's a poor analogy. I would say comparatively this is of higher quality evidence than that.

This is direct measurements of effect with some categories showing evidence of a good probability, that is indirect finding.
Barely reaching statistical significance isn't even remotely the same as "good probability"


I think the HDL and Triglycerides findings showed good probability.
Good probability of a tiny effect size is not really anything too exciting, though.
Ok. Good thing I didn’t represent it as exciting evidence.

Reducing T2D meds is something to get excited about


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Offline CarbShark

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Re: LCHF and healthy eating
« Reply #637 on: June 03, 2018, 07:08:37 PM »
Well, it wasn't intended as a promotion for LCHF and no one said it did promote LCHF diet for T2D. It is more evidence supporting LCHF diets over the standard care diet for Type 2 Diabetes.

FWIW, as I said before, reducing medications needed for T2D is a pretty big deal. That's by itself is worth the price of admission.

It has nothing to do with LCHF diets in specific. It was a study of low- and moderate- carbohydrate diets. The term "LCHF" was not even mentioned in the study.

No, but several (not all) of the studies included meet the criteria for LCHF. And if you actually read even just the abstract you'd realize that one of the issues they raised was specifically about the terminology used to refer to these diets.
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Offline CarbShark

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LCHF and healthy eating
« Reply #638 on: June 03, 2018, 07:52:16 PM »
At the risk of beating a dead horse, which, I guess I'm prone to do, let's look at this quote from the guy accusing me of misrepresenting the study in question. 

You said it represented evidence supporting LCHF diets over the standard care diet for Type 2 Diabetes" when in fact it said nothing at all about LCHF diets. It actually concluded that moderate-low carb diets "may promote favourable outcomes in terms of HbA1c, triglycerides and HDL cholesterol" but the results are inconclusive and patient adherence is problematic; it also said that the existing research literature is mostly biased so "clarity" is needed.

(Below are the results and conclusions from the study, with emphasis added)

JA Says:
Quote
"in fact it said nothing at all about LCHF diets."

The fact is that the authors specifically mentioned that there is no consensus on how to refer to these diets. Several of the studies included meet the criteria for LCHF diets.

JA Says:
Quote
"It actually concluded that moderate-low carb diets "may promote favourable outcomes in terms of HbA1c, triglycerides and HDL cholesterol" but the results are inconclusive"

It actually does not use the word "inconclusive" at all. He seems to be assuming that using the word "may" rather than "definitely does" is the same as "inconclusive."

Further, he ignores the caveat on HbA1c, where they explain those results may be understated due to the effect of subjects stopping their medication during the studies (that would reduce the affect of the LC diet lowering HbA1c).

And, they did not use the word "may" at all when the study says "The LCIA demonstrated reduced requirements for diabetes medication" So just this one line negates his argument that this study does not have evidence that favors LCHF diets over standard of care.

JA says:
Quote
" and patient adherence is problematic"

Well, no they said it was "an issue." they did not use the word "problematic" and that means something different.

And, as for the adherence issues they raised, it's not that big of a deal. The dieters did not strictly adhere to the minimal carb intakes in the studies with the strictest levels (<20g and <50g) But they did lower their total carb intake much more than the other diets, both as a proportion of calories and actual grams, and got more benefit. That's hardly "problematic."

JA says:
Quote
"it also said that the existing research literature is mostly biased so "clarity" is needed."

Well, no, that's not what they said. They ran an analysis that found specific reasons for risk of bias (mostly non-double-blinding, for the diet trials included in this analysis).

But nowhere did they relate bias to the need for clarity. That's just JA making shit up again.

"Clarity" is used only in reference to the terminology used to refer to LC diets.

Read for yourselves.  Decide who is misrepresenting the authors and who is changing the meaning of their study.


The interpretation and effect of a low-carbohydrate diet in the management of type 2 diabetes: a systematic review and meta-analysis of randomised controlled trials | European Journal of Clinical Nutrition
Quote
Eighteen studies (n = 2204) were eligible for inclusion within the systematic review. The definition of a low-carbohydrate diet varied. At trial end, the descriptive analysis suggested that the low-carbohydrate intervention arm (LCIA) may promote favourable outcomes in terms of HbA1c, triglycerides and HDL cholesterol. The LCIA demonstrated reduced requirements for diabetes medication, which may have reduced the observed benefit of dietary carbohydrate restriction on HbA1c. Seven studies provided data to be included in the meta-analyses at 1 year. The meta-analyses showed statistical significance in favour of the LCIA for HbA1c (estimated effect = −0.28%, 95% CI −0.53 to −0.02, p = 0.03; χ 2 = 13.15, df = 6, p = 0.03; I 2 = 54%), HDL cholesterol (estimated effect = 0.06 mmol/L, 95% CI 0.04–0.09, p < 0.00001; χ 2 = 6.05, df = 6, p = 0.42; I 2 = 1%), triglycerides (estimated effect = −0.24 mmol/L, 95% CI −0.35 to −0.13, p < 0.0001; χ 2 = 1.88, df = 6, p = 0.93; I 2 = 0%) and systolic blood pressure (estimated effect = −2.74 mmHg, 95% CI −5.27 to −0.20, p = 0.03; χ 2 = 10.54, df = 6, p = 0.10; I 2 = 43%). Meta-analyses for weight, total cholesterol, LDL cholesterol and diastolic blood pressure did not demonstrate a statistically significant difference between interventions.

Dietary adherence was an issue in most studies. A very low-carbohydrate diet (<50 g/day) seems unrealistic in this population, however, a low-carbohydrate diet (<130 g/day) appears to be achievable. Improved clinical outcomes were observed in some studies as a result of achieving a low- or moderate-carbohydrate diet.

Fifteen out of 18 studies were considered high risk of bias, with performance bias being a common issue.

Conclusions
Reducing dietary carbohydrate may produce clinical improvements in the management of type 2 diabetes.

Further research is needed to understand the true effect of dietary carbohydrate restriction on HbA1c independent of medication reduction and to address known issues with adherence to this dietary intervention.

Clarity is needed regarding appropriate classification of a low-carbohydrate diet.
« Last Edit: June 04, 2018, 11:30:30 AM by CarbShark »
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Online jt512

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Re: LCHF and healthy eating
« Reply #639 on: June 03, 2018, 09:24:21 PM »
Why wait until it is complete, unless you want to change the methodology to suit a particular result - which is unscientific, but it is what we are taught to do.

Be careful about projecting the inadequacies of your field onto the rest of science.

You'd do well to heed your own advice.

Huh?  Care to explain?

Correct me if I'm wrong, but you appear to apply principles of subjective statistics to scientific questions.

Yup, which is just what scientists do.  Classical statistics doesn't answer the question "given the accumulated data, how likely is the hypothesis."  So scientists have to make that call—gasp—using their subjective judgment.  Or, they have to formally use formal Bayesian statistics, which—gasp—begin with subjective priors.  In fact, both classical and Bayesian statistics require subjective judgments about how to model experimental data.  You're ignorant if you think that science, or even data, is "objective."
« Last Edit: June 03, 2018, 09:38:50 PM by jt512 »
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Re: LCHF and healthy eating
« Reply #640 on: June 03, 2018, 09:31:08 PM »
Why wait until it is complete, unless you want to change the methodology to suit a particular result - which is unscientific, but it is what we are taught to do.

Be careful about projecting the inadequacies of your field onto the rest of science.

I wasn't talking about my own field specifically (which is physics, if the name didn't give it away).  I was talking about science in general.  It is a recognised problem (Steve Novella mentioned this at some point on the podcast, don't remember which episode, and there are repositories available where people can submit there methodology in advance of their study results).  It's also visible in the analysis of published literature, with publication bias.  You can make a negative finding into a positive finding, if you change what you are looking for when your null hypothesis doesn't work out the way you want.  You can change your P value to basically anything you want in order to get a required result too.

All that is indeed true, but I don't think the problem is science-wide.  Experimental psychology and medicine, yeah, but I don't see much of that going on in chemistry or high-energy physics, for instance.

Quote
Sadly, I have been taught these lesson by several well regarded people from different disciplines at 'quality' universities...

I'm surprised that as a physics student you were taught such shoddy statistics.  I've done some reading on the statistics that physicists use—at least, high energy physicists—and it's pretty impressive stuff.  And I have a friend who's an astrophysicist who does some very interesting and rigorous work in signal processing.
« Last Edit: June 04, 2018, 04:27:12 AM by jt512 »
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Offline gmalivuk

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Re: LCHF and healthy eating
« Reply #641 on: June 03, 2018, 10:34:54 PM »
Okay, fine, it is evidence, but of very low quality.

Just like finding a new exoplanet is low-quality evidence of alien life.

That's a poor analogy. I would say comparatively this is of higher quality evidence than that.

This is direct measurements of effect with some categories showing evidence of a good probability, that is indirect finding.
Barely reaching statistical significance isn't even remotely the same as "good probability"


I think the HDL and Triglycerides findings showed good probability.
Good probability of a tiny effect size is not really anything too exciting, though.
Ok. Good thing I didn’t represent it as exciting evidence.

Reducing T2D meds is something to get excited about
It might be. What are the numbers on that?
The world is so exquisite with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories for which there's little good evidence. Far better...is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides.

Online John Albert

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Re: LCHF and healthy eating
« Reply #642 on: June 04, 2018, 01:45:10 PM »
Well, no they said it was "an issue." they did not use the word "problematic" and that means something different.

And, as for the adherence issues they raised, it's not that big of a deal. The dieters did not strictly adhere to the minimal carb intakes in the studies with the strictest levels (<20g and <50g) But they did lower their total carb intake much more than the other diets, both as a proportion of calories and actual grams, and got more benefit. That's hardly "problematic."

That's your own (non-professional) opinion. The study actually said:

     
Quote
Dietary adherence was an issue in most studies. A very low-carbohydrate diet (<50 g/day) seems unrealistic in this population, however, a low-carbohydrate diet (<130 g/day) appears to be achievable.

<130 g/day is not very low for a daily carb intake. It's almost certainly not low enough to induce ketosis in most humans.

Adherence issues were judged to be "an issue" with the <50 g/day diets. Less than 50g per day is considered the norm for keto diets. For reference, the Atkins diet recommends less than 20g per day for its ketogenic "induction" phase and between 30-80 g/day for its long-term "balancing" phase. 


JA says:
Quote
"it also said that the existing research literature is mostly biased so "clarity" is needed."

Well, no, that's not what they said. They ran an analysis that found specific reasons for risk of bias (mostly non-double-blinding, for the diet trials included in this analysis).

They specifically said:

     
Quote
Fifteen out of 18 studies were considered high risk of bias, with performance bias being a common issue.

High risk of bias in 15 out of 18 studies. That's 84%, a pretty significant majority.

It also says performance bias was common. Do you know what "performance bias" means? It means (inadvertently or deliberately) introducing undocumented confounding variables into the experiment group. It's pretty common in non-blinded studies done by ideologically-motivated researchers, because knowing which subjects are in the experiment group tends to influence them to influence the results toward their preferred conclusion.

This kind of bias is also prevalent in the kinds of crappy alt-med studies that exhibit clinically significant results. You should listen to Mark Crislip's Quackcast if you're interested in learning some things about critical analysis of medical studies.
« Last Edit: June 04, 2018, 03:16:00 PM by John Albert »

Online John Albert

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Re: LCHF and healthy eating
« Reply #643 on: June 04, 2018, 02:00:33 PM »
You're ignorant if you think that science, or even data, is "objective."

Objectivity is an ideal of experimental science. That's where scientific skepticism comes in, and why peer review, professional critique, and independent replication are so important. 

You still didn't answer my question. Can a single, unreplicated study from untrustworthy sources working outside their field of expertise represent objective evidence? 
« Last Edit: June 04, 2018, 02:05:42 PM by John Albert »

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Re: LCHF and healthy eating
« Reply #644 on: June 04, 2018, 02:15:04 PM »
You're ignorant if you think that science, or even data, is "objective."
Can a single, unreplicated study from untrustworthy sources working outside their field of expertise represent objective evidence?

Can a replicated study from trustworthy sources working in their field represent objective evidence, when subjective judgments entered into every stage of the study design, data collection, analysis, interpretation of the results, conclusions, and the peer review?
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