low-carb kicks butt in studies - again

http://www.cnn.com/2004/HEALTH/diet....eut/index.html

Headline from CNN:

Reports: Low-carb has mixed results
Tuesday, May 18, 2004 Posted: 8:55 AM EDT (1255 GMT)

WASHINGTON (Reuters) -- Low-carbohydrate diets help people lose weight
in the short term but work no better than other diets after a year,
researchers reported on Monday.


The actual abstracts, read the conclusions:

*******
A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat
Obesity and Hyperlipidemia

A Randomized, Controlled Trial
William S. Yancy, Jr., MD, MHS; Maren K. Olsen, PhD; John R. Guyton,
MD; Ronna P. Bakst, RD; and Eric C. Westman, MD, MHS

18 May 2004 | Volume 140 Issue 10 | Pages 769-777

Background: Low-carbohydrate diets remain popular despite a paucity of
scientific evidence on their effectiveness.

Objective: To compare the effects of a low-carbohydrate, ketogenic
diet program with those of a low-fat, low-cholesterol, reduced-calorie
diet.

Design: Randomized, controlled trial.

Setting: Outpatient research clinic.

Participants: 120 overweight, hyperlipidemic volunteers from the
community.

Intervention: Low-carbohydrate diet (initially, 20 g of carbohydrate
daily) plus nutritional supplementation, exercise recommendation, and
group meetings, or low-fat diet (30% energy from fat, 300 mg of
cholesterol daily, and deficit of 500 to 1000 kcal/d) plus exercise
recommendation and group meetings.

Measurements: Body weight, body composition, fasting serum lipid
levels, and tolerability.

Results: A greater proportion of the low-carbohydrate diet group than
the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At
24 weeks, weight loss was greater in the low-carbohydrate diet group
than in the low-fat diet group (mean change, –12.9% vs. –6.7%; P
0.001). Patients in both groups lost substantially more fat mass
(change, –9.4 kg with the low-carbohydrate diet vs. –4.8 kg with the
low-fat diet) than fat-free mass (change, –3.3 kg vs. –2.4 kg,
respectively). Compared with recipients of the low-fat diet,
recipients of the low-carbohydrate diet had greater decreases in serum
triglyceride levels (change, –0.84 mmol/L vs. –0.31 mmol/L [–74.2
mg/dL vs. –27.9 mg/dL]; P = 0.004) and greater increases in
high-density lipoprotein cholesterol levels (0.14 mmol/L vs. –0.04
mmol/L [5.5 mg/dL vs. –1.6 mg/dL]; P 0.001). Changes in low-density
lipoprotein cholesterol level did not differ statistically (0.04
mmol/L [1.6 mg/dL] with the low-carbohydrate diet and –0.19 mmol/L
[–7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects
were more frequent in the low-carbohydrate diet group.

Limitations: We could not definitively distinguish effects of the
low-carbohydrate diet and those of the nutritional supplements
provided only to that group. In addition, participants were healthy
and were followed for only 24 weeks. These factors limit the
generalizability of the study results.

Conclusions: Compared with a low-fat diet, a low-carbohydrate diet
program had better participant retention and greater weight loss.
During active weight loss, serum triglyceride levels decreased more
and high-density lipoprotein cholesterol level increased more with the
low-carbohydrate diet than with the low-fat diet.

**************

The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets
in Severely Obese Adults: One-Year Follow-up of a Randomized Trial
Linda Stern, MD; Nayyar Iqbal, MD; Prakash Seshadri, MD; Kathryn L.
Chicano, CRNP; Denise A. Daily, RD; Joyce McGrory, CRNP; Monica
Williams, BS; Edward J. Gracely, PhD; and Frederick F. Samaha, MD

18 May 2004 | Volume 140 Issue 10 | Pages 778-785


Background: A previous paper reported the 6-month comparison of weight
loss and metabolic changes in obese adults randomly assigned to either
a low-carbohydrate diet or a conventional weight loss diet.

Objective: To review the 1-year outcomes between these diets.

Design: Randomized trial.

Setting: Philadelphia Veterans Affairs Medical Center.

Participants: 132 obese adults with a body mass index of 35 kg/m2 or
greater; 83% had diabetes or the metabolic syndrome.

Intervention: Participants received counseling to either restrict
carbohydrate intake to 30 g per day (low-carbohydrate diet) or to
restrict caloric intake by 500 calories per day with 30% of calories
from fat (conventional diet).

Measurements: Changes in weight, lipid levels, glycemic control, and
insulin sensitivity.

Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg
for persons on the conventional diet. Differences between groups were
not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). For
persons on the low-carbohydrate diet, triglyceride levels decreased
more (P = 0.044) and high-density lipoprotein cholesterol levels
decreased less (P = 0.025). As seen in the small group of persons with
diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c
levels improved more for persons on the low-carbohydrate diet. These
more favorable metabolic responses to a low-carbohydrate diet remained
significant after adjustment for weight loss differences. Changes in
other lipids or insulin sensitivity did not differ between groups.

Limitations: These findings are limited by a high dropout rate (34%)
and by suboptimal dietary adherence of the enrolled persons.

Conclusion: Participants on a low-carbohydrate diet had more favorable
overall outcomes at 1 year than did those on a conventional diet.
Weight loss was similar between groups, but effects on atherogenic
dyslipidemia and glycemic control were still more favorable with a
low-carbohydrate diet after adjustment for differences in weight loss.

******

Low-carb outperformed low-fat in both studies, both in weight loss and
in lipid profile improvement and yet the headline suggests that this
was "mixed results". Another example of studies showing clear results
and the purveyors of the message changing the message entirely.

Now we have scientific evidence that low-carb works and is healthy
over a one year period.

TC

I always wonder how they call 2 kg, about 4 pounds, not significant. It's
pretty darn significant in my life!



Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg
for persons on the conventional diet. Differences between groups were
not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20).



--
Bob in CT
Remove ".x" to reply

"Bob in CT" wrote in message
news
I always wonder how they call 2 kg, about 4 pounds, not significant. It's
pretty darn significant in my life!

Actually (in case you weren't just joking), the scientific method employs a
test of statistical significance to account for variables not included (and
therefore not controlled) in the studies between two groups. Thus, there
can be a difference that mathematically may not be statistically significant
because of these factors.

Oops! Sorry! I've been reading "Scientific American.

On 5/18/2004 10:32 AM, Bob in CT wrote:
I always wonder how they call 2 kg, about 4 pounds, not significant.
It's pretty darn significant in my life!



Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg
for persons on the conventional diet. Differences between groups were
not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20).




If you are maintaining that is probably the range that you are working
within.

--
jmk in NC

Bob in CT wrote in
news
Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ±
8.4 kg for persons on the conventional diet. Differences between
groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P
= 0.20).

I always wonder how they call 2 kg, about 4 pounds, not significant.
It's pretty darn significant in my life!

In statistics, "significant" doesn't mean "personally meaningful." In this
case, it means that there would be a 20% chance of finding a difference of
at least 1.9 kg purely as a result of "luck of the draw" in choosing these
particular samples, even if there were no difference in the underlying
populations. In other words, you don't have a whole lot of confidence that
you'd be able to replicate that particular result.

On Tue, 18 May 2004 09:47:03 -0500, Jim Bard wrote:


"Bob in CT" wrote in message
news
I always wonder how they call 2 kg, about 4 pounds, not significant.
It's
pretty darn significant in my life!

Actually (in case you weren't just joking), the scientific method
employs a
test of statistical significance to account for variables not included
(and
therefore not controlled) in the studies between two groups. Thus, there
can be a difference that mathematically may not be statistically
significant
because of these factors.

Oops! Sorry! I've been reading "Scientific American.



That is true, but sometimes the math should be damned. 4 pounds is
significant. Granted, the analysis includes "11 to 19 pounds (5 to 9 kg)
for the low-carb group and 7 to 19 pounds (3 to 9 kg) for the low-fat
group," so the ranges overlap. However, if the average is 4 pounds,
that's significant. And this, of course, depends on what type of
"average" they were taking. I assume it's the mean and not the median.
Also, there's no indication in the CNN article that they took bodyfat
measurements. I'd hazard a guess that the overall fat loss of the low
carb was greater than the fat loss of the low fat.

--
Bob in CT
Remove ".x" to reply

Bob in CT wrote:

I always wonder how they call 2 kg, about 4 pounds, not significant.
It's pretty darn significant in my life!

That's not what makes a difference significant though.

Think of it like this... suppose there's a factory that makes a widget
with an average weight of 1.5 lbs, but is supposed to vary in size from
1 - 2 lbs.

On average, you'd expect any individual widget to weigh 1.5 lbs. It you
weigh one and it weighs 2 lbs, that's not surprising, you know it's
*supposed* to have that much variance. But if you weigh 10 items, and
the average weight of those 10 is 2 lbs, you start to get suspicious
that something is wrong. If you measure 100 and they average is a 2 lb
weight, you're almost certain something is wrong. If you measure 1000
and the average weight is 2 lbs, something is almost *definetly* wrong.
The significance of your conslusion that something is wrong increases
with the sample size.

Given that retooling a factory is an expensive proposition, you want to
be pretty sure about the error before fixing it. In each case of
testing, you're comparing a sample to the whole population and guessing
what is true about that population based on the sample. In the case of
one sample, you're not very sure about the population at all, but in the
case of 100 samples, you have more certainty about what is going on.

There's mathematical formulas from statistics that basically measure how
significant a measurement is, how likely it is that a sample describes
the population. My example shows that sample size is one variable in
such equations, but there's other variables as well... for example, how
much consistency there is in a bunch of measurements.

It's not about the size of the measurement at all... I can rewrite the
above example to use micrograms or tons instead of pounds and the
example still works. It's about how likely a set of limited
measurements correlates to the entire population (most of which you
haven't measured).

Significance is basically a measure of how confident you can be that a
particular conclusion is actually true, not how big the conclusion
itself is.


Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg
for persons on the conventional diet. Differences between groups were
not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20).

p = 0.20 is a description of the measurable significance, and this is a
very low measure, comparable to just one widget's weight being off in
our example above. It means they consider this to possibly be just luck
and can't know if it's real for the population without more study.

p = 1 means that something is 100%, absolutely, certainly true - you
can't ever get p = 1 short of measuring the entire population. And
measuring the entire population isn't doing an experiment anymore, that
is life, the universe and everything.

Generally, a scientist wants p 0.90 or 0.95 or 0.99. Which
cut-off is acceptable depends on the specific type of study.

But p = 0.2 *definetly* is not good enough to say the differences
between those groups is true (for that particular measurement, other
measurments in the study are significant).

So in summary, they are saying they measured a difference, but the
difference isn't meaningful enough to signify anything beyond what
happened to their sample.

--
As you accelerate your food, it takes exponentially more and more energy
to increase its velocity, until you hit a limit at C. This energy has
to come from somewhere; in this case, from the food's nutritional value.
Thus, the faster the food is, the worse it gets.
-- Mark Hughes, comprehending the taste of fast food

On 18 May 2004 14:58:35 GMT, Eric Bohlman wrote:

Bob in CT wrote in
news
Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ±
8.4 kg for persons on the conventional diet. Differences between
groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P
= 0.20).

I always wonder how they call 2 kg, about 4 pounds, not significant.
It's pretty darn significant in my life!

In statistics, "significant" doesn't mean "personally meaningful." In
this
case, it means that there would be a 20% chance of finding a difference
of
at least 1.9 kg purely as a result of "luck of the draw" in choosing
these
particular samples, even if there were no difference in the underlying
populations. In other words, you don't have a whole lot of confidence
that
you'd be able to replicate that particular result.

That is true, but P values can be overrated. If you get one that's 0.001,
does that mean that it's always going to be reproduced? From what I've
seen, no. One study will have certain results and another will have the
opposite results, and both will have P values that make them seem great.
Personally, I think that 4 pounds is significant, and I don't think that a
P value of 0.2 means that it's not significant. Of course, there's no
real data here -- perhaps two people lost 19 pounds on low carb while only
one person lost 19 pounds onlow fat. So, you can't really see what's
going on without access to the data.

--
Bob in CT
Remove ".x" to reply

tcomeau wrote:

snip abstracts of two studies

Ah, this has more info than the media reports.

There's the expected results that the lipid profiles and glycemic
control of low-carbers prove low-carb is the healthier diet, but there's
other important bits.

First, the low-carb diet in each study did not include calorie
restriction, whereas the low-fat diet *did*. Thus the fact that
low-carbers actually ate fewer calories than low-fatters is a
significant effect of the diet itself. You eat fewer calories without
trying. Good stuff for weight loss.

Secondly is the retention rate. It is not broken down in the second
study, but is in the first study. Three quarters of the low-carbers
completed the first study as opposed to only half the low-fatters.
since I assume these groups had no large differences in willpower, it
appears that much less "butching up" is necessary on low-carb.

These studies together show that a low-carb diet is both healthier and
easier than a low-calorie/low-fat diet.

--
As you accelerate your food, it takes exponentially more and more energy
to increase its velocity, until you hit a limit at C. This energy has
to come from somewhere; in this case, from the food's nutritional value.
Thus, the faster the food is, the worse it gets.
-- Mark Hughes, comprehending the taste of fast food

A couple of things not mentioned in this version of the research. 1. By
your guidelines the first must be tossed, it had atkins grant money
involved. The first also was only 24 weeks, the second reflects other
similar research, after 1 year weight status was not significantly
different. The most intresting results, again reflecting other such
research, is that trigs are lower and hdl higher in lc.

2. By the end the daily calorie intake was similar, in the year long
study, the lead researcher says:

" Dr. Linda Stern, who led the study, said it confirmed that any diet
that cuts calories will work.

"Americans are overweight because we're eating too much food and
ingesting too many calories," she said in a statement."

Also of interest is the high drop out rate in both diets in both studies
and the compliance problem. This too reflects that most people fail after
a time in maintaining weight status regardless of diet approach, either
these two diet types or others.



http://www.cnn.com/2004/HEALTH/diet....eut/index.html

Headline from CNN:

Reports: Low-carb has mixed results
Tuesday, May 18, 2004 Posted: 8:55 AM EDT (1255 GMT)

WASHINGTON (Reuters) -- Low-carbohydrate diets help people lose weight
in the short term but work no better than other diets after a year,
researchers reported on Monday.


The actual abstracts, read the conclusions:

*******
A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat
Obesity and Hyperlipidemia

A Randomized, Controlled Trial
William S. Yancy, Jr., MD, MHS; Maren K. Olsen, PhD; John R. Guyton,
MD; Ronna P. Bakst, RD; and Eric C. Westman, MD, MHS

18 May 2004 | Volume 140 Issue 10 | Pages 769-777

Background: Low-carbohydrate diets remain popular despite a paucity of
scientific evidence on their effectiveness.

Objective: To compare the effects of a low-carbohydrate, ketogenic
diet program with those of a low-fat, low-cholesterol, reduced-calorie
diet.

Design: Randomized, controlled trial.

Setting: Outpatient research clinic.

Participants: 120 overweight, hyperlipidemic volunteers from the
community.

Intervention: Low-carbohydrate diet (initially, 20 g of carbohydrate
daily) plus nutritional supplementation, exercise recommendation, and
group meetings, or low-fat diet (30% energy from fat, 300 mg of
cholesterol daily, and deficit of 500 to 1000 kcal/d) plus exercise
recommendation and group meetings.

Measurements: Body weight, body composition, fasting serum lipid
levels, and tolerability.

Results: A greater proportion of the low-carbohydrate diet group than
the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At
24 weeks, weight loss was greater in the low-carbohydrate diet group
than in the low-fat diet group (mean change, 12.9% vs. 6.7%; P
0.001). Patients in both groups lost substantially more fat mass
(change, 9.4 kg with the low-carbohydrate diet vs. 4.8 kg with the
low-fat diet) than fat-free mass (change, 3.3 kg vs. 2.4 kg,
respectively). Compared with recipients of the low-fat diet,
recipients of the low-carbohydrate diet had greater decreases in serum
triglyceride levels (change, 0.84 mmol/L vs. 0.31 mmol/L [74.2
mg/dL vs. 27.9 mg/dL]; P = 0.004) and greater increases in
high-density lipoprotein cholesterol levels (0.14 mmol/L vs. 0.04
mmol/L [5.5 mg/dL vs. 1.6 mg/dL]; P 0.001). Changes in low-density
lipoprotein cholesterol level did not differ statistically (0.04
mmol/L [1.6 mg/dL] with the low-carbohydrate diet and 0.19 mmol/L
[7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects
were more frequent in the low-carbohydrate diet group.

Limitations: We could not definitively distinguish effects of the
low-carbohydrate diet and those of the nutritional supplements
provided only to that group. In addition, participants were healthy
and were followed for only 24 weeks. These factors limit the
generalizability of the study results.

Conclusions: Compared with a low-fat diet, a low-carbohydrate diet
program had better participant retention and greater weight loss.
During active weight loss, serum triglyceride levels decreased more
and high-density lipoprotein cholesterol level increased more with the
low-carbohydrate diet than with the low-fat diet.

**************

The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets
in Severely Obese Adults: One-Year Follow-up of a Randomized Trial
Linda Stern, MD; Nayyar Iqbal, MD; Prakash Seshadri, MD; Kathryn L.
Chicano, CRNP; Denise A. Daily, RD; Joyce McGrory, CRNP; Monica
Williams, BS; Edward J. Gracely, PhD; and Frederick F. Samaha, MD

18 May 2004 | Volume 140 Issue 10 | Pages 778-785


Background: A previous paper reported the 6-month comparison of weight
loss and metabolic changes in obese adults randomly assigned to either
a low-carbohydrate diet or a conventional weight loss diet.

Objective: To review the 1-year outcomes between these diets.

Design: Randomized trial.

Setting: Philadelphia Veterans Affairs Medical Center.

Participants: 132 obese adults with a body mass index of 35 kg/m2 or
greater; 83% had diabetes or the metabolic syndrome.

Intervention: Participants received counseling to either restrict
carbohydrate intake to 30 g per day (low-carbohydrate diet) or to
restrict caloric intake by 500 calories per day with 30% of calories
from fat (conventional diet).

Measurements: Changes in weight, lipid levels, glycemic control, and
insulin sensitivity.

Results: By 1 year, mean (±SD) weight change for persons on the
low-carbohydrate diet was 5.1 ± 8.7 kg compared with 3.1 ± 8.4 kg
for persons on the conventional diet. Differences between groups were
not significant (1.9 kg [95% CI, 4.9 to 1.0 kg]; P = 0.20). For
persons on the low-carbohydrate diet, triglyceride levels decreased
more (P = 0.044) and high-density lipoprotein cholesterol levels
decreased less (P = 0.025). As seen in the small group of persons with
diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c
levels improved more for persons on the low-carbohydrate diet. These
more favorable metabolic responses to a low-carbohydrate diet remained
significant after adjustment for weight loss differences. Changes in
other lipids or insulin sensitivity did not differ between groups.

Limitations: These findings are limited by a high dropout rate (34%)
and by suboptimal dietary adherence of the enrolled persons.

Conclusion: Participants on a low-carbohydrate diet had more favorable
overall outcomes at 1 year than did those on a conventional diet.
Weight loss was similar between groups, but effects on atherogenic
dyslipidemia and glycemic control were still more favorable with a
low-carbohydrate diet after adjustment for differences in weight loss.

******

Low-carb outperformed low-fat in both studies, both in weight loss and
in lipid profile improvement and yet the headline suggests that this
was "mixed results". Another example of studies showing clear results
and the purveyors of the message changing the message entirely.

Now we have scientific evidence that low-carb works and is healthy
over a one year period.

TC