The Latest Diet Study
A couple of weeks ago, the diet news was full of the recent study in the New England Journal of Medicine comparing several diet groups eating different amounts of fat, protein, and carbohydrate. The result was widely reported as being that all diets are the same, and that the only important thing was to cut calories. I even heard one commentator on TV say "this should put the question to rest".
Uh, not really. Here are some of the reasons why not:
1) There was no low-carbohydrate group. The researchers were careful to label the different diets according to their protein and fat composition rather than carbohydrate, e.g. "Low Fat, Average Protein". Was this reported in the news? It was not. The group the media called "low-carbohydrate" was instructed to eat 35% of their calories from carbohydrate (which I would call a "moderate-carb diet"). In any case, that group did not follow the instructions. The so-called "High Fat, High Protein group" continued eating exactly the same percentage of carbohydrate as before the diet (though since they were eating fewer calories, they were eating less of everything including carbs).
When Dr. Frank Sacks, the lead researcher, was asked why a low-carbohydrate group was not included, he reportedly stated, "People don't stick with low-carbohydrate intake and we didn't want to try anything unrealistic." Furthermore they concluded that because urinary ketosis tends to decrease over time among people on low-carb diets that it is "futile to sustain a low intake of carbohydrates". (I guess weight control, blood glucose control, blood pressure control, and improved blood lipids are not nearly as important as "urinary ketosis".)
I'm going to resist going on a tirade, but I will just say that there are plenty of people who for medical reasons must restrict their diets. No one is going to tell someone with a wheat allergy that it would be too hard to give up wheat. But it seems fine to suggest that giving up high-carb foods is just too darned difficult, even if our health depends on it, which is the case for many people. In fact, on the NPR show Science Friday, Dr. Sacks reported that the prediabetics in the study had a better response to the lower-carb diets (diabetics were excluded).
2) The groups, in fact, turned out to be not all that different in their eating, despite the instructions that they were given, though the low-fat groups were eating somewhat less fat and more carbohydrate. I found it puzzling that there was no speculation as to why this was the case. It was especially myterious that all groups reduced the percentage of fat in their diets, even the two "high fat" groups! I have to wonder if there was low-fat bias in the support groups.
3) The diets were all calorie-controlled. Participants were instructed to subtract 750 calories from their usual intake, and ended up eating 300-400 calories less. Considering the diets were pretty similar and that they were all calorie-controlled, it's not surprising that similar results were obtained. On the other hand, we know that in studies of truly low-carb diets, people tend to lose more weight, even when calories are the same as other diet groups.
In any case, although the groups lost about the same amount of weight (average 9 pounds kept off for two years), there was a very strong effect related to whether or not the study participants attended the support groups -- the ones who attended the most regularly lost the most weight. Unfortunately, there is no analysis as to why people participated more. For example, someone who found that they were chronically hungry, or for whom the diet wasn't working may have stopped going to the group.
Also of note was the variation within the groups, which was much more than the variation between the groups. A small percentage lost more than 40 pounds, while "some, no matter how dedicated, did not lose weight." I wonder what would have happened if those people had tried an actual low-carb diet.
Have a comment about this study? You can submit to the New England Journal of Medcine until March 11!
Photo © Paul Preacher
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Hear! Hear! My boyfriend, who, after 9 years remains mystified (a skeptic) of my low-carb lifestyle, insisted this study showed I could eat more carbs than I do now and still remain healthy as long as my caloric intake was also low.
I have type 2 diabetes and PCOS (and for added metabolic fun, I also have Hashimoto’s thyroid disease). I must live ketogenic low-carb or go back on insulin shots.
I simply do not, and I repeat do not lose weight on anything but a truly low-carb plan. In fact, I gained weight on Weight Watchers. I gained weight on Biggest Loser. I even gained weight on South Beach, Zone, and Sugar Busters. Yes, I get tired of low carb monk-hood and test the waters from time to time only to regret it later.
I am sticking to my under 40 carb per day plan. I am off insulin, my lipid profile is perfect and my A1c is an astounding 5.1.
If I could eat what I wanted based only on calories I would. I have been low-carbing since 1997 and am sick of it. BUT I do believe that I am alive today because I gave up most carbs. Atkins changed my life when I lost 150 lbs in 13 months on it many years ago (and keep it off doing low-carb).
Thank you so much for pointing out the flaws in this so-called study. If they had put a group of type 2 diabetics (insulin resistant women, or even prediabetics) in this study and carbed them up, boy the outcome would have been very different!
I just KNEW you’d have a more in-depth scoop on this study! Thanks for sharing your insight, Laura. You help a LOT of people!