Blank Check

Low Carb, Low Fat, Null Result, Blank Check

JAMA is out with a big, important study of low fat versus low carb dietary strategies. And the study has a null result on three hypotheses the researchers were testing. The results showed no differences in outcomes between the study groups. Low fat was no better than low carb. Also, neither genetic nor insulin secreting profiles made any difference. That’s it. Back to the drawing board.

Using a Null Result as a Blank Check

However, it’s very tempting to misuse a null result as proof for cherished beliefs. In their discussion, the researchers did a little bit of this. They wrote in their discussion:

We conclude that when equal emphasis is given to high dietary quality for both low-fat and low carbohydrate eating plans, it is not helpful to preferentially direct an individual with high insulin secretion status who is seeking weight loss to follow a lower-carbohydrate eating plan instead of a lower-fat eating plan.

Of course, that “conclusion” is an opinion. It’s not a finding supported by this experiment. This study is a really good study, but it’s not a study of dietary quality. It’s a study of two high quality diets.

But no matter, the New York Times took the bait. They blasted out headlines saying:

The Key to Weight Loss Is Diet Quality, Not Quantity, a New Study Finds

Anahad O’Connor goes on to write that people need not pay attention to calories or portion sizes. What really matters is eating vegetables and whole foods, according to his article. Just avoid sugar and processed foods. Everything will work out fine.

Further Embellishment

Further embellishment on the findings came from Dariush Mozaffarian, who told O’Connor:

This is the roadmap to reducing the obesity epidemic in the United States. It’s time for us and other National policies to stop focusing on calories and calorie counting.

These are all reasonable opinions, but they are not what the study proved. They are just a few of the principles that the investigators used when they designed the intervention. Many other principles came into the study – self-awareness, goal setting, and physical activity – just to name a few.

But the study didn’t test those principles. So it’s not proof that they all work. Some or all of them might be quite helpful. (We have serious doubts about advice to ignore portion sizes.)

Let’s be clear, though. This study is not a roadmap for solving the obesity epidemic. And it’s not proof that calories and portions don’t matter.

It’s just proof that either low carb or low fat dietary strategies can work equally well for losing weight. Nothing more. Nothing less.

Click here for the study and here for the puffery from the Times. For more balanced reporting on the study, click here.

Blank Check, photograph © stateofplace / flickr

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February 21, 2018