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“A vegetarian Atkins diet is almost an oxymoron.” Dean Ornish, MD
Low-Carb Diet Back—Again
Our local newspaper carried the following headline on the front page above the fold: Study ‘Vindication’ for Low-Carb Diet.
It must’ve been a slow news day, because that heading overshoots the facts. More appropriate is the headline on page D1 of The Wall Street Journal: "Study Fuels Low-Fat vs. Low-Carb Debate."
The study takes the Atkins-type diet off life support--but it hardly merits front-page treatment. Once you know the details, there’s little that’s really new or surprising.
Let’s sort out the facts, and try to put them into proper perspective.
The 2-year study, funded by the Robert Atkins foundation and reported in the July 17, 2008, New England Journal of Medicine, randomly assigned 322 moderately obese subjects into one of three diets: low-fat, Mediterranean, and low-carb. Calories were restricted in the first two diets, while the low-carb diet limited carbohydrate intake to 20 grams per day for two months, and then gradually increased to120 grams. All three groups ended up eating about the same number of calories.
The low-carb group lost an average of 10.3 pounds, the Mediterranean group lost 10 pounds, and the low-fat group lost 6.5 pounds. The low-carb group reduced the ratio of total cholesterol to HDL “good” cholesterol by 20%, compared to 16% in the Mediterranean group and 12% in the low-fat group. (Low ratio is better.)Levels of LDL “bad” cholesterol did not change significantly within the groups. Harmful triglycerides decreased significantly in the low-carb group compared to the low-fat group (24mg vs. to 3mg). Finally, those on the Mediterranean diet (<35% fat, rich in vegetables, poultry and fish instead of red meat) did best in controlling blood sugar levels.
It has been known for more than a century that low-carb diets cause rapid weight loss (losing 10 pounds over two years was certainly no surprise). The concern has been that the saturated fat typically found in low-cab diets might drive up cholesterol. So it was a bit of a surprise that the low-carb diet lowered the cholesterol ratio more than the other diets.
How did this happen?
The Researchers said: “The results imply that dietary composition modifies metabolic biomarkers [such as cholesterol].” Otherwise, they do not attempt to explain why the low-carb group had more change in cholesterol ratio than the low-fat group.
Dr. Dean Ornish, a well-known advocate of extremely low fat diets, does offer an explanation.
Ornish said the study should not be seen as an endorsement of the Atkins diet—for two reasons. First, the low-fat diet was not really low in fat; it included 30% fat, far more than the 10% he and others, such as Dr. Caldwell Esselstyn, recommend. More importantly, he points out that the low-carb group was encouraged to consume vegetable fats, as opposed to the meat fats Atkins dieters typically eat. “A vegetarian Atkins diet is almost an oxymoron,” Ornish commented.
Does the Atkins diet bring to mind soy burgers? Our local newspaper apparently didn’t think so; under the front-page headline it featured a color photo of two juicy cuts of raw red meat.
Another issue, raised by the researcher themselves, is the setting in which the study was conducted. “One might argue,” they wrote, “that the unique nature of the workplace in the study, which permitted a closely monitored dietary intervention for a period of two years, makes it difficult to generalize the results to other free-living populations.”
The subjects worked at Israel’s Nuclear Research Center and ate lunch (the main meal in Israel) in the Center cafeteria—aided by color-coding to show the diet group: red for low-fat, green for Mediterranean, and blue for low-carb. In addition, subjects were regularly queried about compliance away from the workplace.
As Ornish indicated, the low-carb group was “counseled to choose vegetarian sources of fat and protein and to avoid trans fat.” To encourage compliance, cafeteria offerings were also labeled to show calories and grams of carbohydrate, fat, and saturated fat. Moreover, each food item was marked with either a colored full circle (indicating “Feel free to consume”), a colored half circle (Consume in moderation), or a blank circle (Don’t touch!).
It was a wonderful arrangement, to be sure, but hardly a real-world situation. Dr. Iris Shai, the study leader, said the research center was a good place to run the study because it is isolated and people seldom leave. Doesn’t seem much like fending for yourself at home or McDonalds or even Subway, does it?
Clinically Acceptable Alternatives
Just as aerobic exercise was once thought to be practically synonymous with health—while weight training was viewed as mainly cosmetic—low-fat diets have often been presented as the only sanctioned weight-loss diet. The Israeli researchers believe their study lays the groundwork for other alternatives. Dr. Shai said, “We believe that this study will open clinical medicine to considering low-carb and Mediterranean diets as safe, effective alternatives for patients.”
Here’s the study’s carefully worded conclusion: “Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individual tailoring of dietary interventions.”
Many doctors and nutrition experts would probably concur that a low-carb diet—especially one emphasizing vegetable fats and fish over animal fats—is an acceptable alternative for weight control, particularly for sedentary people. It’s not a wise choice for hard training athletes, however.
As Chris Carmichael wrote in his Food for Fitness (Putman, 2004), high intensity exercise is impossible without adequate carbohydrates; fat simply cannot supply energy fast enough to support maximum performance. That doesn’t mean low-carb diets have no merit, however. “Considering the fact that low-intensity exercise can be beneficial for primarily sedentary people and that low-intensity exercise may be sustainable on a low-carb diet,” Carmichael reasons, “sedentary people may benefit from low-carb diets.” (For more details see http://www.cbass.com/Carbs_Athletes.htm )
A low-carb diet emphasizing vegetable sources of fat and protein may also a suitable alternative for lowering triglycerides. It is generally recognized that excess carbohydrates, especially the refined variety, can raise triglyceride levels. Adding or substituting “good fat” can alleviate the problem by slowing the absorption of carbohydrates (glucose). In fact, adding “good” fat cut my triglycerides in half; see http://www.cbass.com/TRIGLYCE.HTM. Adding too much fat, especially saturated fat, can compound the problem, however; see http://www.cbass.com/BADDIET.HTM.
Chose your diet carefully, based on your goals, fitness and health status. If you are unsure, consult your doctor or a registered dietitian.
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Personally, I would not choose the low-carb approach. I tried it many years ago and resolved never to do it again. I felt tired and couldn’t think properly; see my book Ripped for full details. As an athlete, my muscles and brain need carbohydrates (glucose) to function properly.
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