Just in: results of new Low-Carb diet studies!

From The Omnivore

By Anthony Colpo.

May 19, 2004.

The May 18, 2004 issue of the Annals of Internal Medicine features two new low-carbohydrate-vs-low-fat diet trial reports. I have summarized the findings for readers, and thrown in my ten cents worth after discussing each study. For those who would like to access the original full-text articles, just click on the hyperlinks provided.

Study 1 Atkins versus low-fat diet

William Yancy and his colleagues randomized 120 overweight volunteers to follow either the Atkins Diet or a low-fat, high-carbohydrate diet. The intervention for both groups included group meetings which took place at an outpatient clinic twice monthly for 3 months, then monthly for 3 months. The meetings typically lasted 1 hour and consisted of diet instruction, supportive counseling, questionnaires, and biomedical measurements.

Participants were encouraged to exercise for 30 minutes at least 3 times weekly, but no formal exercise program or incentives were provided.

Following the guidelines presented in Dr. Atkins' New Diet Revolution and additional handouts, trained research staff instructed participants to restrict intake of carbohydrates to less than 20 g/d. The low-carb participants were permitted unlimited amounts of meat, fowl, eggs, fish, and shellfish, 4 oz of hard cheese, 2 cups of salad vegetables (such as lettuce, spinach, or celery), and 1 cup of low-carbohydrate vegetables (such as broccoli, cauliflower, or squash) daily.

When participants were halfway to their goal body weight (determined at the week 10 visit with assistance from research personnel), they were advised to add approximately 5 g of carbohydrates to their daily intake each week until they reached a level at which they could maintain their body weight.

The low-carbohydrate diet group also received daily Atkins Nutritionals, Inc supplements (multivitamin, essential oils, diet formulation, and chromium picolinate; for a list of the composition of these supplements, see below)

Using a commonly available booklet and additional handouts, a registered dietitian instructed participants in the low-fat group to consume less than 30% of calories as fat, less than 10% of calories as saturated fat, and to eat 500 to 1000 calories less than the participant's calculated energy intake for weight maintenance (body weight in pounds x 10).

Food records collected at each visit from a subsample of participants indicate that the low-carbohydrate diet group consumed a mean 30g of carbohydrates, 98g of protein, and 111g of fat daily. The low-fat diet group consumed 198g of carbohydrates, 71g of protein, and 49g of fat daily.

Despite the fact that the low-fat diet group received counseling to restrict overall calorie intake whilst the low-carbohydrate diet group received counseling to restrict intake of carbohydrates only, the estimated daily energy intake was 1461 calories in the low-carbohydrate diet group and 1502 calories in the low-fat diet group.

Results

Dropout rates were higher in the low-fat group; forty-five (76%) of the 59 participants originally assigned to the low-carbohydrate diet group and 34 (57%) of the 60 participants assigned to the low-fat diet group completed the study.

Over 24 weeks, the mean weight loss in the low-carbohydrate diet group was almost twice as great as that in the low-fat group; 12.0 kg versus 6.5 kg, respectively. The proportion of this weight loss derived from fat was 9.4 kg in the low-carbohydrate diet group and 4.8 kg for the low-fat diet group.

For those who still insist that the weight reduction seen on low-carb diets is derived primarily from water loss, the mean change in total body water was –2.4 kg in the low-carbohydrate diet group and –1.8 kg in the low-fat diet group, a negligible difference.

In addition to experiencing greater average weight loss and lower attrition, a higher proportion of the low-carb participants lost greater than 10% of their initial body weight; 61% versus 23%, respectively.

The low-carbohydrate diet group also showed more beneficial changes in blood triglyceride levels and HDL levels than did the low-fat diet group.(1)

Adverse Effects

Several adverse effects occurred more frequently in the low-carbohydrate diet group than in the low-fat diet group, including constipation 68% vs. 35%, headache (60% vs. 40%), bad breath (38% vs. 8%), muscle cramps (35% vs. 7%), diarrhea (23% vs. 7%), general weakness (25% vs. 8%), and rash (13% vs. 0%). A 53-year-old male in the low-carbohydrate diet group who had a family history of early heart disease developed chest pain near the end of the study, and coronary heart disease was subsequently diagnosed. During the study, this participant lost 16 kg, his serum LDL cholesterol level decreased by 0.75 mmol/L (29 mg/dL), and his serum HDL cholesterol level increased by 0.21 mmol/L (8 mg/dL).

Comments: A while back, I read commentary on the preliminary data of this study by a couple of anti-low-carb figures who claimed the addition of vitamin and fish oil supplements provided an unfair advantage to the low-carb group. Personally, I believe both groups should have been given the same supplements as a routine measure to ensure that this was purely a diet comparison. As it stands, this study was a comparison of the Atkins diet plus supplements versus a low-fat diet. Nonetheless, if any of the aforementioned jokers truly believe that the ingredients in the supplements provided (see reference 2 below) could produce a 5.5kg weight loss (the difference between the low- and high-carb groups), then they might be interested in some prime swamp-, er, I mean, prime real estate I've got for sale at a bargain price...

The side effects noted in the low-carb group are worthy of further mention. No doubt the incidence of constipation could be reduced by increasing the miniscule intake of low-carb plant foods that was prescribed in this study. The participants could have obtained far more roughage than that provided in 3 piddling cups of veggies without endangering their low-carb status. The greater incidence of headache and general weakness seems to me symptomatic of low-blood sugar episodes, which is going to be a reality for many people when they consume only 30g of carbs per day. Many folks will also have to get used to the idea of ketosis breath if they are going to opt for ketogenic low-carb plans. I have nothing but the greatest admiration and respect for the late Dr. Atkins, but as I have said several times before, many people will benefit from keeping their carb intakes a little higher than the average level seen in this study.

Despite these drawbacks, it is interesting to see that a notably greater number of participants dropped out in the low-fat group. This parallels the findings of almost every low-carb vs low-fat study reporting drop-outs that I have come across.

This study was financed by a research grant from the Robert C. Atkins Foundation, New York, NY. No doubt this will bring charges from the anti-low-carb crowd of researcher bias, despite at least one of the lead researchers publicly admitting that he had fully expected the Atkins diet to perform poorly. Eric Westman told BBC reporters: "We didn't expect that the diet would do very well. We weren't really expecting to find much weight loss at all. It was also a very extreme diet so that we thought people would have difficulty staying on it."(3) According to a disclosure statement in the Annals paper, "Investigators at Duke University conducted the study and maintained exclusive control of all data and analyses. The funding source had no involvement in the recruitment of participants; study interventions; collection, analysis, or interpretation of the data; or preparation or review of the manuscript."

Study 2 Fat loss in Philly

The second paper appearing in the Annals reported on a study conducted by researchers from Philadelphia Veterans Affairs Medical Center. Readers may remember the 6-month report of this study as one of two papers that attracted widespread media attention when they appeared in the New England Journal of Medicine this time last year. Well, the researchers involved decided to see who was still standing (figuratively speaking, of course) among the participants of this trial after one year, and to report their progress.

Of the 132 indivdiuals who commenced the study, 45 dropped out after 1 year; 20 persons in the low-carbohydrate group and 25 in the conventional low-fat diet group.

Those who read the NEJM report from last year will know that after 6 months the low-carb group lost an average 5.8kg, compared to only 1.9kg on the high-carb, low-fat diet. After 1-year, the average weight loss was 5.1kg in the low-carbohydrate group and 3.1kg in the high-carb diet group. The difference in weight loss between the 2 diet groups was not statistically significant.

HDL levels increased and triglyceride levels decreased more in the low-carbohydrate group than in the high-carb diet group, an effect that was independent of weight loss.

The difference in blood glucose levels and insulin sensitivity between diet groups by 1 year was not significant, although hemoglobin A1c levels in the portion of subjects with diabetes decreased more in the low-carbohydrate group. Two persons on the low-carbohydrate diet and 4 on the conventional diet developed diabetes after 1 year.

Adverse Reactions

One person on the low-carbohydrate diet was hospitalized with noncardiac chest pain during the third month of the study. Two persons in the low-carbohydrate group died, including one who died of complications of hyperosmolar coma 5 months into the study and another who had severe ischemic cardiomyopathy and died suddenly 10 months after study enrollment. Laboratory values obtained 14 days before this person's death showed no electrolyte abnormalities.

Comments: Triglyceride, HDL cholesterol, and hemoglobin A1c levels showed greater improvements among the low-carb diet group at 12 months, but no statistically significant difference in weight loss was evident.

A look at the dietary composition data shows why the low-carb diet produced such a lacklustre result in weight loss during the last six months of the study; by 12 months, most of the subjects were no longer following a low-carb diet! Average carb intake was 120g, while protein had declined from baseline, from 84g to an anaemic 73g. Compliance with the diet, evidently, was poor.

Nonetheless, this raises an important point. The study by Gary Foster, et al, which also appeared in the May 22, 2003 issue of the NEJM, showed a deterioration in compliance among both the low-carb and low-fat groups. While the low-carb group showed notably greater weight loss at the 6-month point, after 12 months the weight loss difference between the two groups was again not significant.

Critics of low-carb diets have jumped on these observations, claiming that they prove low-carb diets are hard to adhere to. If this is the argument they are going to stick with, they better realize that published head-to-head comparisons with low-carb diets indicate that low-fat diets are even harder to stick to.

The truth is, a great many people are going to find the going tough no matter what diet they choose to follow. Personally, I find sticking to a low-carb diet requires about as much discipline as lying on a tropical beach, and numerous other low-carbers I have corresponded with have shared similar sentiments. Still, for many people, adopting a low-carbohydrate diet will mean a considerable departure from their usual habits, and the going will not be easy.

As research shows that behavioral modifications can significantly affect the attrition and success rate of one's weight loss efforts, the time is probably ripe for some serious, in-depth research into this aspect of dieting.

Our hunter-gatherer ancestors did not have the option of eating highly-processed, refined carbohydrate-rich junk, nor did they have the option of sitting on their butts all day. They had to get up and expend energy in their search for food - if not, they starved! Not surprisingly, our Paleolithic forebears were untroubled by obesity.

The reason so many of us are in such attrocious shape nowadays is because we are presented with choices not available to our ancestors; the choice to eat wholesome filling food, or nutrient-depleted, craving-inducing crap; the choice to engage in regular physical activity, or to succumb to mechanization's ability to completely remove the need for physical activity from of our lives.

It's going to take a lot more than hyperbolic weight loss claims to convince the bulk of the population to opt for the healthier of these choices on a long-term basis...

References

1. Yancy WS, et al. A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia: A Randomized, Controlled Trial. Annals of Internal Medicine, 2004; 140: 769-777.

2. Supplements (provided by Atkins Nutritionals, Inc., New York, NY):

Multivitamin formula (administered daily as 6 capsules): vitamin A as acetate (3000 IU); vitamin A as ß-carotene with mixed carotenoids (1200 IU); vitamin C (360 mg); vitamin D3 (400 IU); vitamin E (300 IU); vitamin B1 (50 mg); vitamin B2 (50 mg); niacin (40 mg); vitamin B6 (50 mg); folate (1600 mg); vitamin B12 (800 mcg); vitamin K (10 µg); biotin (600 µg); pantothenic acid (120 mg); calcium (500 mg); magnesium (250 mg); zinc (50 mg); selenium (200 µg); manganese (10 mg); chromium (600 µg); molybdenum (60 µg); potassium (20 mg); inositol hexanicotinate (100 mg); choline bitartrate (100 mg); para-amino benzoic acid (100 mg); vanadyl (80 µg); N-acetyl-l-cysteine (120 mg); pantethine (150 mg); quercetin (100 mg); boron (2 mg); grapeseed extract (40 mg); green tea (80 mg); and lecithin extracts, garlic, arginine, licorice, bromelain, pantethine, spirulina, inulin, lactoferrin, bioperine, and acidophilus, in unspecified amounts.

Essential oil formula (administered daily as 3 capsules): flaxseed oil (1200 mg), borage seed oil (1200 mg), fish oil (1200 mg), vitamin E (15 IU).

Diet formula (administered daily as 6 capsules): citrin (2700 mg), chromium (1200 µg), soy extract (9000 mg), methionine (1500 mg), L-carnitine (3000 mg), vitamin B6 (120 mg), pantethine (120 mg), asparagus (300 mg), parsley (300 mg), kelp (120 mg), spirulina (300 mg), potassium citrate (594 mg), magnesium (360 mg), L-glutamine (450 mg), dl-phenylalanine (900 mg), L-tyrosine (450 mg), piperine (30 mg).

3. The Atkins Diet. BBC Two, Jan 22, 2004.
http://www.bbc.co.uk/science/horizon/2004/atkinstrans.shtml

4. Stern L, et al. The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial. Annals of Internal Medicine, 2004; 140: 778-785.

5. Samaha FF, et al. A low-carbohydrate diet as compared with a low fat diet in severe obesity. New England Journal of Medicine, May 22, 2003; 348: 2074-2081.

Anthony Colpo is an independent researcher and certified fitness consultant with 20 years' experience in the physical conditioning arena. To contact: contact@theomnivore.com

Disclaimer: This article is presented for information purposes only and is not intended as medical advice. Persons with medical conditions should institute dietary changes whilst being monitored by a competent medical practitioner.

© Anthony Colpo 2004. Copyright information:

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