More Evidence Supports Low-Carbohydrate Diet  

Bottom Line:

A low-carbohydrate diet may reduce weight to a greater extent than a
low-fat diet in the short term, but this advantage appears to
disappear by one year.

A low-carbohydrate diet may produce some lasting improvements in lipid
profiles when compared with a low-fat diet.

May 17, 2004  Two randomized trials reported in the May 18 issue of
the Annals of Internal Medicine further support the efficacy of a
low-carbohydrate diet. A six-month trial showed higher participation
and greater weight loss, and a 12-month study showed similar weight
loss but better lipid profile than with a conventional diet. The
editorialist uses findings from both studies to advise physicians and
patients.

"This diet can be quite powerful. We found that the low-carb diet was
more effective for weight loss," lead author Will Yancy, MD, from Duke
University Medical Center and the Veterans Affairs Medical Center in
Durham, North Carolina, says in a news release. "We also found
cholesterol levels seemed to improve more on a low-carb diet compared
to a low-fat diet."

In this study, which is the first randomized controlled trial of an
Atkins-style diet, 120 study participants were assigned to a
low-carbohydrate, high-protein diet or a low-fat, low-cholesterol,
low-calorie diet.

The low-carbohydrate group (<20 g/day) was allowed daily unlimited
calories, animal foods (meat, fowl, fish, and shellfish), and eggs, as
well as 4 oz of hard cheese, two cups of salad vegetables (lettuce,
spinach, or celery) and one cup of low-carbohydrate vegetables
(broccoli, cauliflower, or squash). They also received daily
nutritional supplements including a multivitamin, essential oils, an
Atkins diet formulation, and chromium picolinate.

The low-fat, low-cholesterol, low-calorie group received less than 30%
of daily caloric intake from fat, less than 10% of calories from
saturated fat, and less than 300 mg cholesterol daily. They were
advised to restrict daily calories by 500 to 1,000 calories less than
their maintenance diet.

At study entry, all subjects were between 18 and 65 years of age and
in generally good health, with a body mass index (BMI) between 30 and
60, and a total cholesterol level greater than 200 mg/dL. None had
dieted or used weight loss medications in the previous six months. All
subjects were encouraged to exercise 30 minutes at least three times
per week and had regular group meetings at an outpatient research
clinic for six months.

The study was completed by 76% of participants in the low-carbohydrate
diet group and by 57% of participants in the low-fat diet group (P =
.02). At six months, weight loss was -12.9% in the low-carbohydrate
diet group and -6.7% in the low-fat diet group (P < .001).

In both groups, loss of fat mass (change, -9.4 kg with the
low-carbohydrate diet vs. -4.8 kg with the low-fat diet) was greater
than loss of fat-free mass (change, -3.3 kg vs. -2.4 kg,
respectively). Compared with the low-fat diet group, the
low-carbohydrate diet group 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 = .004) and greater increases in
high-density lipoprotein [HDL] cholesterol levels (0.14 mmol/L vs.
-0.04 mmol/L [5.5 mg/dL vs. -1.6 mg/dL]; P < .001).

Changes in low-density lipoprotein (LDL) cholesterol level were not
significantly different between groups (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 = .2). However, participants in the low-carbohydrate
diet group had more minor adverse effects, such as constipation and
headaches, than did patients in the low-fat diet group.

Study limitations include inability to distinguish effects of the
low-carbohydrate diet and those of the nutritional supplements
provided only to that group, and use of healthy participants followed
for only 24 weeks, limiting generalizability of the study results.

The authors are currently testing whether a low-carbohydrate diet can
improve glycemic control in diabetes. However, they warn that patients
with medical conditions such as diabetes and hypertension or who use
diuretics should not begin a low-carbohydrate diet without close
medical supervision, because the diet affects hydration and blood
glucose levels. Nor do they recommend an Atkins-type diet for
individuals attempting to lose weight for the first time.

"Over six months the diet appears relatively safe, but we need to
study the safety for longer durations," Dr. Yancy says, noting
potential long-term health risks including elevations in LDL
cholesterol, bone loss, or kidney stones.

The Robert C. Atkins Foundation funded this research. The study
authors have no financial interest in Atkins Nutritionals, Inc.

In the second study, by Linda Stern, MD, from the Philadelphia
Veterans Affairs Medical Center in Pennsylvania, and colleagues, 132
obese adults were randomized to receive counseling to either restrict
carbohydrate intake to less than 30 g per day (low-carbohydrate diet)
or to restrict caloric intake by 500 calories per day with less than
30% of calories from fat (conventional diet). At baseline, BMI was at
least 35 kg/m2, and 83% of participants had diabetes or metabolic
syndrome.

By one year, mean weight change was -5.1 ± 8.7 kg in the
low-carbohydrate diet group and -3.1 ± 8.4 kg in the conventional diet
group (difference, -1.9 kg; 95% confidence interval [CI], -4.9 to 1.0
kg; P = .20). The low-carbohydrate diet group fared better in terms of
greater decrease in triglyceride levels (P = .044) and less decrease
in HDL cholesterol levels (P = .025).

In the subgroup of 54 persons with diabetes, hemoglobin A1c levels
improved more with the low-carbohydrate diet, but the difference was
not statistically significant in sensitivity analyses. Both groups had
similar changes in other lipids and in insulin sensitivity.

Study limitations include high dropout rate of 34% and suboptimal
dietary adherence.

"Despite modest overall weight loss in both diet groups, assignment to
the low-carbohydrate group had a direct and more favorable effect on
triglyceride level, HDL cholesterol level, and glycemic control in the
smaller subgroup of patients with diabetes," the authors write. "These
findings give further evidence that restriction of carbohydrates in
obese persons, who may be overconsuming carbohydrates at baseline, may
have favorable metabolic effects. Caution is still needed, however, in
recommending a low-carbohydrate diet, as important concerns remain."

The Veterans Affairs Healthcare Network supported this study. The
authors report no potential financial conflicts of interest.

"We can no longer dismiss very-low-carbohydrate diets," Walter C.
Willett, MD, DrPH, from the Harvard School of Public Health in Boston,
Massachusetts, writes in an accompanying editorial.

"We can encourage overweight patients to experiment with various
methods for weight control, including reduced-carbohydrate diets, as
long as they emphasize healthy sources of fat and protein and
incorporate regular physical activity," he concludes. "Patients should
focus on finding ways to eat that they can maintain indefinitely
rather than seeking diets that promote rapid weight loss. For many
patients, the roll will have little role."

Dr. Willett served as an unpaid consultant on a grant by the Atkins
Foundation.

Ann Intern Med. 2004;140:769-777, 778-785, 836-837

Clinical Context

Obesity has reached epidemic proportions in the U.S., and many
patients are desperate to find a solution to help them lose weight.
The strategy of low-carbohydrate dieting has been espoused by a
growing number of obese individuals, and their choice is validated
with some evidence of efficacy. In a six-month analysis published in
the May 22, 2003, issue of the New England Journal of Medicine
involving the same patient cohort currently reexamined at one year by
Stern and colleagues, a low-carbohydrate diet was associated with
greater weight loss and improved triglyceride levels, insulin
sensitivity, and glycemic control when compared with a low-fat diet.

An editorial by Willett that accompanies the current study by Stern
cautions that the improved short-term weight gain associated with
low-carbohydrate diets when compared with low-fat diets has generally
not been shown to be significantly different at one year. He also
notes that weight is not the only area to be scrutinized with
low-carbohydrate diets. Low-carbohydrate diets have been demonstrated
to have favorable effects on the lipid profile and insulin sensitivity
that could improve health outcomes in obese adults.

Two studies in the current issue of the Annals of Internal Medicine
compare the effects of low-carbohydrate vs. low-fat diets.

Study Highlights

Yancy article:
Subjects were primarily white, well-educated, and female. The average
BMI was slightly greater than 34 kg/m2, and all participants had
hyperlipidemia. Patients using prescription medication other than
thyroid replacement or female hormonal treatments were excluded.
Diet interventions were accomplished using group counseling sessions.
Participants in the low-carbohydrate diet group were instructed to
initially limit carbohydrate to less than 20 g per day and then add 5
g of carbohydrate per day later. The low-fat diet group was instructed
to reduce caloric intake by 500 to 1,000 kcal per day, derive less
than 30% of these calories from fat, and consume less than 300 mg of
cholesterol per day.

The main study outcomes were weight loss and weight loss derived from
fat over a 6-month period. Metabolic parameters were also followed.
120 subjects were randomized, and 76% and 57% of the low-carbohydrate
and low-fat diet subjects, respectively, completed the study.

Mean weight loss was 12 kg in the low-carbohydrate diet group at the
end of the study compared with 6.5 kg in the low-fat diet group.

Fat mass was reduced by 9.4 kg in the low-carbohydrate diet group
compared with a reduction of 4.8 kg in the low-fat diet group.

Triglyceride and HDL cholesterol levels were significantly improved in
the low-carbohydrate diet group compared with the low-fat diet group.
Mean LDL cholesterol levels were similar between the 2 groups,
although 2 subjects in the low-carbohydrate diet group stopped the
study because of increased LDL levels.

More subjects in the low-carbohydrate diet group experienced adverse
events, the most common of which were constipation, headache,
halitosis, and muscle cramps.

Stern article:
Subjects included adults with a BMI of 35 kg/m2 or greater without
significant renal or hepatic disease.

Participants were randomized to either a low-carbohydrate diet, which
limited carbohydrate intake to less than 30 g per day, or a low-fat
diet, in which less than 30% of calories were derived from fat and
overall caloric intake was reduced by 500 kcal per day. These
interventions were implemented through weekly counseling sessions for
4 weeks, and then monthly sessions for 11 months.

The main study outcome was weight change, and subjects were also
followed for effects on serum lipids, insulin sensitivity, and
glycemic control.

More than 80% of study participants were men and had either metabolic
syndrome or diabetes.

20 of 64 original subjects in the low-carbohydrate diet group dropped
out of the study prior to one year compared with 25 of 68 patients in
the low-fat diet group.

Both intervention groups had reduced average daily caloric intake by
one year to similar levels. The low-carbohydrate diet group had
reduced carbohydrate intake by 52% at one year.

Although patients in the low-carbohydrate diet group had lost
significantly more weight than the low-fat diet group by 6 months,
they averaged no more weight loss during the following 6 months and
had a mean one-year weight loss of 5.1 kg. This was statistically
similar to the one-year mean weight loss of 3.1 kg for patients in the
low-fat diet group, whose mean weight decreased steadily during the
trial.

Total and LDL cholesterol levels were fairly stable in both
intervention groups at one year, and the difference between treatment
groups was not significant. However, triglyceride and HDL cholesterol
levels were more improved in the low-carbohydrate diet group compared
with the low-fat diet group.

Serum glucose levels and insulin sensitivity were similar between the
diet groups at one year, although hemoglobin A1c improvements in
subjects with diabetes in the low-carbohydrate diet group narrowly
missed statistical significance.

No, my experience is that I still have reflux issues if I cheat and eat
something on the do not eat list (white carbs like sugar or flour). That
would not be what you would expect if slow digestion of fat were responsible
for the disorder. And of course on the weight loss side, I find low carbing
easier to deal with. On low fat, I was so hungry I couldn't sleep, and I
would give up after a couple of months with only a small weight loss due to
being so TIRED. I agree about avoiding Frankenfoods. They are really
expensive additionally.

The resulting decades of IMHO bad diet advice that came from the incorrect
application of conclusions of the Framingham study then. Same difference if
you are on the consumer side. It was flawed advice. One of the low carb
books I read by a doc in California, and I can't recall the name of the
author this AM, stated that her type 2 patients who had been placed on low
fat diets, had less success in controlling their diabetis than the ones who
"cheated" and ate meat. So, although Akins and South Beach diets are
designed by Cardiologists, there are docs in other medical fields who have
started recommending low carb to their patients because they see the
advantages. I will see if I can find that information.

The joke is that I now find the same

I have no clue what you are talking about.

Joy

I would also be careful with anything trying to join the bandwagon as
low-carb.

For example, low carb wraps. These are popular with the low carb
dieters, and they have been selling well. But the store where I work
just informed us that the 6 wraps with 8 net carbs or less are
actually 8-12 carbs. They had us take down the signs advertising he 8
carbs, but I have yet to see any notices to inform the customers of
the truth. So, all these people are still buying the sandwiches,
thinking they are lower, and they don't realize they may be messing up
their diet.

Also, the wraps have small portions, so the price is the same, yet you
get less than half the meat of a regular sandwich. It's cheaper to buy
your wrap and make your own sandwich.

Personally, I am embarrassed to sell them. I wouldn't mind if poeple
knew the portions were lower (or the price was lower), and if the
customers knew the correct carb count. I really believe the company
should have put up notices to correct the false claim. But then, this
may have been their plan all along.

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