A friend wrote in email:

> Does the Atkins diet cause muscle loss?

It is a claim that some opponents of the diet make. For example, this page claims it at the same time as some myths about Atkins which are definitely not true. I couldn't find any evidence that, for a given amount of calories, having them be low carb significantly increased muscle loss. One thing to note is that a low-calorie diet, regardless of the calorie composition, will cause some muscle loss. Its normal. But a high-calorie Atkins diet shouldn't (tho you also won't lose fat as quickly).

This study used 3 diets, low-carb, zone, and low-calorie for 3 months. They all lost weight and there was no difference in fat or lean body mass loss.

J Okla State Med Assoc 2002 May;95(5):329-31	Related Articles, Links 


Effect of weight loss plans on body composition and diet duration.


Landers P, Wolfe MM, Glore S, Guild R, Phillips L.

Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, PO Box 26901-CHB 469, Oklahoma City, Oklahoma City, OK 73190, USA.

Are low carbohydrate high protein (LCHP) diets more effective in
promoting loss of weight and body fat and can individuals stay on an
Atkins-like diet more easily than on a conventional weight loss diet?
A pre-test/post-test randomized group design composed of three cohorts
was utilized to test 1) a LCHP ketogenic diet; 2) the Zone diet; and
3) a conventional hypocaloric diabetic exchange diet that supplied <
10%, 40%, and 50% of calories from carbohydrate, respectively. Body
composition was measured before and after the intervention treatment
period with dual energy X-ray absorptiometry. Mean weight loss was 5.1
kg for those who completed the 12-week program. There were no
significant differences in total weight, fat, or lean body mass loss
when compared by diet group. Attrition was substantial for all plans
at 43%, 60%, and 36% for LCHP, Zone and conventional diets,
respectively.

PMID: 12043107 [PubMed - indexed for MEDLINE]

This study put fat kids on a low-carb diet. "Body composition studies indicated that weight was lost equally from all areas of the body and was predominantly fat... Lean body mass was not significantly affected"

Pediatrics 1998 Jan;101(1 Pt 1):61-7	Related Articles, Links 


The effects of a high-protein, low-fat, ketogenic diet on adolescents with
morbid obesity: body composition, blood chemistries, and sleep
abnormalities.


Willi SM, Oexmann MJ, Wright NM, Collop NA, Key LL Jr.

Department of Pediatrics, Medical University of South Carolina, Charleston 29425, USA.

OBJECTIVE. To evaluate the efficacy and metabolic impact of a
high-protein, low-carbohydrate, low-fat ketogenic diet (K diet) in the
treatment of morbidly obese adolescents with initial weights of >200%
of ideal body weight. METHODS. Six adolescents, aged 12 to 15 years,
weighing an average of 147.8 kg (range, 120.6-198.6 kg) and having an
average body mass index of 50.9 kg/m (39.8-63.0 kg/m), consumed the K
diet for 8 weeks. Daily intake consisted of 650 to 725 calories, which
was substantively in the form of protein (80-100 g). The diet was very
low in carbohydrates (25 g) and fat (25 g). This was followed by 12
weeks of the K diet plus two carbohydrates (30 g) per meal (K+2
diet). MAIN OUTCOME MEASURES. Anthropometric data and blood and urine
were collected at enrollment, during week 1, and at 4-week intervals
throughout the course of the study. Resting energy expenditure was
measured by indirect calorimetry. Body composition was estimated using
dual-energy x-ray absorptiometry, bioelectrical impedance analysis,
and urinary creatinine excretion at enrollment and on completion of
each phase of the diet. Nocturnal polysomnography and multiple sleep
latency testing were conducted at baseline and repeated after an
average weight loss of 18.7 kg to determine sleep architecture,
frequency and duration of apneas, and daytime
sleepiness. RESULTS. Subjects lost 15.4 +/- 1.4 kg (mean +/- SEM)
during the K diet and an additional 2.3 +/- 2.9 kg during the K+2
diet. Body mass index decreased 5.6 +/- 0.6 kg/m(2) during the K diet
and an additional 1.1 +/- 1.1 kg/m(2) during the K+2 diet. Body
composition studies indicated that weight was lost equally from all
areas of the body and was predominantly fat. Dual-energy x-ray
absorptiometry showed a decrease from 51.1% +/- 2.1% body fat to 44.2%
+/- 2.9% during the K diet and then to 41.6% +/- 4.5% during the K+2
diet. Lean body mass was not significantly affected. Weight loss was
accompanied by a reduction in resting energy expenditure of 5.2 +/-
1.8 kcal/kg of fat-free mass per day. Blood chemistries remained
normal throughout the study and included a decrease in serum
cholesterol from 162 +/- 12 to 121 +/- 8 mg/dL in the initial 4 weeks
of the K diet. An increase in calcium excretion was accompanied by a
decrease in total-body bone mineral content. A paucity of rapid eye
movement sleep and excessive slow-wave sleep were seen in all subjects
at enrollment. Weight loss led to an increase in rapid eye movement
sleep (P < .02) and a decrease in slow-wave sleep (P < .01) to near
normal levels. CONCLUSIONS. The K diet can be used effectively for
rapid weight loss in adolescents with morbid obesity. Loss in lean
body mass is blunted, blood chemistries remain normal, and sleep
abnormalities significantly decrease with weight loss.

PMID: 9417152 [PubMed - indexed for MEDLINE]

Next, dieting obese females went on a liquid, low-cal, low-carb diet. "The average loss in body mass was 16.2 kg, representing approximately 18% of the average initial body mass. The loss comprised about 20% fat-free tissue and 80% fat tissue." Note that some of that 20% may be something other than muscle.

Int J Obes Relat Metab Disord 1993 Jun;17(6):317-22	Related Articles, Links 


The composition of weight loss in dieting obese females by electrical methods.


Saunders NH, al-Zeibak S, Ryde SJ, Birks JL.

Department of Physics, University of Swansea, Singleton Park, UK.

The fat and fat-free components of the weight loss of a group of obese
females undergoing a clinically monitored dieting regime have been
estimated by two noninvasive electrical techniques, bioelectrical
impedance analysis (BIA) and tissue resonance impedance monitoring
(TRIM). These two procedures are described and results presented for a
group of volunteers representing a wide range of body mass
index. During the 11 weeks of the study the members of the group were
on a 405 kcal liquid ketogenic diet. Within experimental error, the
estimates of changes in body composition by the two methods agree with
each other and also with estimates determined by tritiated water
dilution and neutron activation measurements on the same group of
subjects. The average loss in body mass was 16.2 kg, representing
approximately 18% of the average initial body mass. The loss comprised
about 20% fat-free tissue and 80% fat tissue. The safety, convenience
and non-invasive nature of the electrical techniques makes them useful
additional procedures to be deployed in the routine monitoring of body
composition.

PMID: 8392496 [PubMed - indexed for MEDLINE]

And an extremely low-calorie (starvation) diet, either mixed or low-carb causes mostly fat loss. "Composition of weight lost (percentage) during the ketogenic diet was water 61.2, fat 35.0, protein 3.8. During the mixed diet, composition of loss was water 37.1, fat 59.5, protein 3.4". So the low-carb diet caused 12% more protein loss in this study.

J Clin Invest 1976 Sep;58(3):722-30	Related Articles, Links 


Composition of weight lost during short-term weight
reduction. Metabolic responses of obese subjects to starvation and
low-calorie ketogenic and nonketogenic diets.


Yang MU, Van Itallie TB.

The effects of starvation, an 800-kcal mixed diet and an 800-kcal
ketogenic (low carbohydrate-high fat) diet on the composition of
weight lost were determined in each of six obese subjects during three
10-day periods.The energy-nitrogen balance method was used to quantify
the three measurable components of weight loss; protein, fat, and
water. On the 800-kcal ketogenic diet, subjects lost (mean +/- SE)
466.6 +/-51.3 g/day; on the isocaloric mixed diet, which provided
carbohydrate and fat in conventional proportions, they lost 277.9+/-
32.1 g/day. Composition of weight lost (percentage) during the
ketogenic diet was water 61.2, fat 35.0, protein 3.8. During the mixed
diet, composition of loss was water 37.1, fat 59.5, protein 3.4...

PMID: 956398 [PubMed - indexed for MEDLINE]

This is just common sense, but if you diet without exercising, you are going to lose muscle mass, whereas if you diet *and* exercise, you may not. "The results were eye-opening. While all three groups demonstrated a significant decrease in bodyweight, the diet-only group experienced significant lean mass loss along with the fat loss. In fact, they lost over 30% of their total weight from lean mass. They also showed a decrease in power as determined by 30-second Wingate test. The diet and aerobics group also had less than desirable fat/ muscle loss with almost 25% of total weight loss coming from lean mass. The diet, aerobic and exercise group, however, had outstanding results. They not only lost most of their weight from fat (97%) they also significantly increased their strength in a 1RM test of the bench press and squat, the only group to do so, and showed an increase in peak oxygen consumption. This led researchers to conclude what we already suspected- a weight loss program combining diet, aerobics and strength- training is head and shoulders above any other method currently available."

http://www.protraineronline.com/past/march2000/protrainer7.cfm

And here is someone elses page of abstracts on the subject.

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