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Low Carb Diets - All aspects of low-carb diets discussed here
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Posted by Susan on January 27, 2010, 4:41 pm
x-no-archive: yes
Same weight loss, better BP with low-carb diet vs drug/diet combo
JANUARY 25, 2010 | Shelley Wood
Durham, NC - A new randomized trial comparing a low-carbohydrate diet
with a low-fat diet in combination with the weight-loss drug orlistat
has found that both strategies produced meaningful weight loss among
hospital outpatients over a one-year period [1]. Strikingly, however,
the low-carb diet appeared to produce significant improvements in blood
pressure.
According to Dr William S Yancy Jr (Duke University, Durham, NC), lead
author on the study, this is the first time the low-carb diet has been
pitted against a diet drug in combination with a different diet. It is
also one of the first studies to compare weight-loss strategies in
patients who also have other known medical problems, including high
blood pressure, diabetes, arthritis, etc.
Yancy et al's findings are published in the January 25, 2010 issue of
the Archives of Internal Medicine.
Almost 10% weight loss at one year
Yancy et al's study randomized 146 overweight or obese outpatients (mean
age 52, mean body-mass index [BMI] 39.3) to either a low-carbohydrate,
ketogenic diet, or to orlistat (120 mg, three times daily) and a low-fat
diet over 48 weeks, with regular group meetings to boost diet adherence.
At the end of the study period, weight loss was similar in both groups,
at roughly 10% (approximately 20 to 25 pounds). Of note, almost 80% of
the low-carb group and almost 90% of the orlistat/low-fat group
completed the full 48-week follow-up.
Improvements in HDL and triglycerides were seen in both groups, LDL
levels improved in the orlistat/low-fat diet group only, while glucose,
insulin, and HbA1c levels improved in the low-carb group only, although
none of these differences were statistically meaningful. By contrast,
both systolic and diastolic blood-pressure levels declined in the
low-carb group only, a statistically significant difference between
weight-loss groups.
"It's not surprising that the blood pressure improved," Yancy told
heartwire, adding that improvements in blood pressure are common in
weight-loss trials. "But it was surprising that, with similar weight
loss, blood pressure would improve more in one group than the other."
While there are a number of explanations for the blood-pressure
differences between weight-loss strategies, Yancy speculated that it
might be related to the known diuretic effect of low-carb diets.
"We've looked at that in the past, and it seems to occur in the first
couple weeks of the diet and doesn't seem to be a big factor after that,
but that could contribute to the differences seen here. The other thing
is that low-carb diets are thought to reduce insulin levels more so than
a high-carb diet. There are several different mechanisms that insulin
has with the vascular system that might cause increased blood pressure,
so if you decrease insulin your blood pressure might decrease as well."
No significant differences in lipid changes
Other low-carb diet studies have also reported improvements in lipid
parameters compared with low-fat diets: something that was not seen in
the current study to a statistically significant degree. Yancy
attributes this in part to an aggressive attempt on the part of
investigators to include as many patients as possible at the 48-week
follow-up.
"A big criticism of other weight-loss trials is there are a lot of lost
or missing data," he explained. "We tried to avoid that as much as
possible, and as a result, some of these folks who came back for their
final measurements who hadn't really been following their diets kind of
watered down the results."
For example, in the paper, the authors report differences in
heart-disease risk factors at interim time points and note that, out to
36 weeks, the two interventions "appeared to have differential effects
on fasting serum lipid and lipoprotein levels over the first 36 weeks,"
but that "these differences converged by 48 weeks."
In another important finding, Yancy et al point out that while a small
number of study participants initiated hypertension or diabetes
medications over the course of the study in both diet groups, a much
higher number actually decreased or discontinued their dosages, with a
higher proportion of patients discontinuing or lowering their dosages in
the low-carb group.
Referring to the blood-pressure effects of the low-carb diet, Yancy
pointed out that investigators "don't really know the full effect of the
diet intervention because patients were actually taking less medication."
Options for patients
The key message from the paper is not that one diet is superior to
another, Yancy concluded. "Different interventions appeal to different
people," he told heartwire. "We have a big weight problem in our
society, and this study gives us two different options, both of which
worked quite well. And if you happen to have blood-pressure problems and
you are trying to kill two birds with one stone, the low-carb option
might be a better option than the orlistat option."
Of note, he added, orlistat is not associated with increases blood
pressure, although other diet drugs are, including sibutramine, for
which the FDA recently released an updated warning on CVD risks.
Yancy, as well as second author Dr Eric C Westman (Duke University
Medical Center) disclosed having received clinical research grants from
the Robert C Atkins Foundation.
Source
Yancy Jr WS, Westman EC, McDuffie JR, et al. A randomized trial of a
low-carbohydrate diet vs orlistat plus a low-fat diet for weight loss.
Arch Intern Med 2010; 170:136-145.
Related links
Low-carb diets hit the headlines again
[Prevention > Prevention; Dec 11, 2009]
Atherosclerosis heightened in mice fed low-carb, high-protein diet
[Prevention > Prevention; Aug 26, 2009]
"Eco-Atkins" plant-based, low-carb diet appears to lower cholesterol
[Lipid/Metabolic > Lipid/Metabolic; Jun 11, 2009]
Fewer calories=less weight, regardless of carb, fat, or protein content
[Prevention > Prevention; Feb 25, 2009]
Slashing carbs cuts medication use, improves or reverses type 2
diabetes, study says
[Brain/Kidney/Peripheral > Brain/Kidney/Peripheral; Jan 09, 2009]
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