Comparing Apples & Scalpels in the NEJM

This is unfolding today in the New England Journal of Medicine. A fascinating little study of 22 patients is offering up a comparison of apples and scalpels today. The researchers compared metabolic effects of weight loss from very low calorie diets and from bariatric surgery. They found similar effects for similar amounts of weight loss. So, the researchers concluded that they could find “no evident clinically important effects independent of weight loss.”

Reducing fat tissue – “by whatever means” – is what matters for diabetes control, said a companion editorial.

Hang On Just a Minute

This is indeed a fascinating study. So it will definitely spark quite a lively conversation.

But we have to say that such sweeping conclusions from only 22 patients might be premature. In fact, this study has a number of limitations that should give pause.

To start with, this is a comparison between very different groups of patients. Of course, it wasn’t randomized. The researchers separately recruited bariatric surgery patients and patients who were willing to go on a very rigorous, low-calorie liquid diet. Either path is difficult, but in very different ways.

It’s also worth noting that getting to a similar amount of weight loss in the diet group was much harder. The withdrawal rate in the diet group was 39 percent for falling short of the targeted weight loss. This was even after rigorous patient selection procedures to emphasize the challenges of following this diet. In other words the investigators knew that getting enough weight loss in the diet group would be hard and they tried to weed out prospects who would not make it. For the folks in the diet group who met the goal, it took much longer than it did for the surgery group.

In short, the comparison here is between two groups of subjects that are clearly not comparable. It’s not apples to apples. Rather, it’s apples to scalpels.

Room for Overreach and Misinterpretation

This study offers much opportunity for learning. But it also opens the door for misinterpretation. It doesn’t show that diet is just as good as bariatric surgery for controlling diabetes. As a practical matter, it isn’t. “Results not typical” is the disclaimer to keep in mind for the diet group in this study. Even in this protocol, with all the effort thrown at the patients in the diet arm, it took seven weeks longer for them to reach the goal. Over and over again, researchers have demonstrated that surgery delivers better metabolic outcomes in patients with type 2 diabetes and obesity.

However, this study does provide good evidence for the potential of any approach that can help people reduce their adiposity. It’s one more piece of the puzzle to confirm that effective obesity care has important health benefits.

Click here for the study and here for the editorial.

Apple and Scalpel, images by Evan-Amos and Dr.phees / Wikimedia Commons

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August 20, 2020