A study was just published in the New England Journal of Medicine on July 17th comparing the effectiveness and safety of three different weight loss diets. 322 moderately obese subjects were assigned to one of three diets: low-fat, restricted-calorie; Mediterranean, restricted-calorie; or low-carbohydrate, non-restricted calorie.
The rate of adherence to the study diet was 95% at year one and 85% at year two. Among the 272 participants who completed the intervention, the mean weight losses were 3.3 kg for the low-fat group, 4.6 kg for the Mediterranean-diet group, and 5.5 kg for the low-carbohydrate group.
Perhaps more significantly, the relative reduction in the ratio of total cholesterol to HDL was 20% in the low carbohydrate group while only 12% in the low-fat group. Among the 35 subjects with diabetes, changes in fasting plasma glucose and insulin levels were more favorable among those assigned to the Mediterranean diet than among those assigned to the low-fat diet.
Unfortunately, the bias against saturated fat and animal products that is still so prevalent in the mainstream (in spite of the lack of evidence to support it) prevailed in this study. The research team advised those following the low-carb diet to “choose vegetarian sources of fat and protein” and moderate their consumption of saturated fats and meat.
This suggests that the low-fat dieters may have consumed a substantial portion of their calories as fat in the form of omega-6 polyunsaturated fatty acids. Excess intake of omega-6 fatty acids contributes to a host of problems including heart disease, diabetes, and cancer; but even more relevant to this study and its results is the fact that omega-6 fatty acids can cause increased water retention. And as everyone knows, increased water retention equals increased weight.
This certainly causes me to wonder how much more dramatic the results of this study might have been if the low-carb subjects were encouraged to significantly restrict their consumption of omega-6 fats (which cause water retention, and thus weight gain) and replace them with saturated fats (which do not cause water retention). What is remarkable is that in spite of the consumption of omega-6 fats, the low-carb group still lost more weight than both the low-fat and Mediterranean groups. That’s a strong endorsement for the benefits of a low-carb diet for weight loss.
The low-carb and Mediterranean (to a lesser degree) diet also had other benefits beyond promoting weight loss and improving cholesterol measures. The level of high-sensitivity C-reactive protein decreased significantly only in the Mediterranean and ow-carb group, with the low-carb group again showing the greatest decrease (29% vs. 21%). C-reactive protein is a measure of inflammation that has been positively correlated with heart disease in recent studies. Once again, one must wonder if the reduction would have been even greater in the low-carb group had the subjects been told to restrict their intake of omega-6 fats, which are known to promote inflammation.
Another interesting finding is that although caloric intake was only restricted in the low-fat and Mediterranean diet groups, the low-carb group also ended up eating fewer calories during the diet. Many people who follow a low-carb, high protein/high fat diet find that they spontaneously eat less because additional protein, and in particular fat, leads to greater levels of satiety (satisfaction).
One limitation of the study is that it relied on self-reported dietary intake (this is true of almost every dietary study except those performed in tightly controlled conditions, such as an inpatient facility). However, the study was somewhat unique in that it was conducted in a workplace at a research center with an on-site medical clinic. It also had several other strengths. The drop-out rate was exceptionally low for a study of this kind; all participants started simultaneously; the duration was relatively long (2 years); the study group was relatively large; and the monthly measurements of weight remitted a better understanding of the weight-loss trajectory than other studies.
Tags: cholesterol, diabetes, diet, lipids, loss, low-carb, obese, weight
I find it extremely telling that the low-carb diet was unrestricted, yet participants still ate roughly the same number of calories and lost more weight than the other groups. I think there’s something about the standard diet that causes hyperphagy. I suspect it’s wheat and possibly sugar.
Tara Parker-Pope (NYT health writer) had the audacity to say the study was designed to vindicate the Atkins diet! Despite the fact that low-carbers were eating ad lib. A portion of the funding came from the Atkins foundation. Those are the conclusions you come to when you’re a stubborn low-fatter with a book out. She’s a chubby one too.
I’m going to add my own post to the fray as well, in case people aren’t already fed up with reading about it.
Thanks for posting on this study. I read tidbits about it in Yahoo news, but there was no indication that the low-carb dieters were told to avoid animal fats. I think you’re right that this poor advice may have kept the low-carbers from having even better results.
My own personal experience is that low-fat diets leave me hungry all the time and I tend to over-eat, especially when I was addicted to foods with added sugar. I lost 30 pounds doing low-carb along with more exercise and minimizing PUFA and eliminating trans-fats. But in the last year my weight loss ended and I actually gained back 7 or 8 pounds. I’d like to lose another 20 pounds, so I’ve started using the 16/8 approach and it seems to be working. You eat during an 8-hour period and then fast for 16 hours. I have dropped from three meals a day to two. Dropping my lightest meal is about 500 to 800 calories per day cut out from what I was eating. So far, I’m encouraged by the results. I’ve lost about 3 pounds in not quite two weeks, though I’m sure it will take many weeks to drop the remaining 17 pounds.
The Yahoo news report interviewed a researcher who mentioned an interesting study with monkeys that were fed diets with high fat, high trans fat, and low fat, but all equal calories over 10 years if I remember correctly. Interestingly, the high fat and low fat monkeys weighed about the same at the end of the study, but the high trans fat monkeys weighed 7% more on average.
The study probably undermined the Atkins diet, because people were told to focus on vegetarian proteins and fats, the worst possible advice, unless the dieters spontaneously ate coconut oil, macadamia, cocoa butter, palm oil, hazelnut, and olive oil for most of their fat. And something tells me they did not do that. It’s well-known that PUFAs are fattening, that’s why animals are fed corn and soybeans. When they try to fatten animals on coconut oil, they become lean and hungry. But if they add just a little PUFA oils (like corn and esp soybeans), the animals become fat. The combination of carbs and PUFA oils seems particularly fattening.
I don’t think you can blame low-fat diets for problems if you are eating food loaded with sugar and flour (including whole grain). The best low-fat diet is Joel Fuhrman, IMO, because he limits grains and bans sugar, flour, and oils. The base of his diet is green vegetables (half raw and half cooked). On the next level of his pyramid are fruits, beans, and potatoes. At the top are raw nuts and seeds. Grains are also at the top and they are optional. Only stuff like brown rice and oatmeal are allowed - not flour, pasta, and bread. I can believe Fuhrman that many people thrive on his diet, because he gets rid of low-nutrient food and focuses on unprocessed foods in their natural form.
I don’t believe anyone will thrive on Dr. Dean Ornish’s horrible diet. Judging by the looks of Dean, he doesn’t seem to be doing well, either. His diet is a total abomination, emphasizing fat-free milk products, egg whites, and flour based pastas, breads, and other nutrient deficient waste.
I wouldn’t say the results were that significant. They may be “statistically” significiant, but I doubt the obese people eating the diets would consider a 5.5 kg average weight loss in 2 years to be significant. Since they say that low-carb dieters 5.5 +/- 7.0 kg, it implies that some of them gained weight, none of them lost much weight, and they rebounded after 1-6 months.
Only the men consistently lost weight. The women sometimes gained. The women on the low-fat diet had a 50/50 chance of losing weight or gaining, approximately. I’m surprised nobody has noticed this. All of the diets were poorly structured and controlled. They should have used Atkins Induction as the low-carb template and Joel Fuhrman as the low-fat template.
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