Is a low-carb diet "no better" than other diets for weight loss or reducing cardiovascular risk?
Or could that negative conclusion be an indication of subtle bias and instead rephrased to say that low-carb diets are just as effective as other diets?
That is one of the points Dr. Bret Scher, Medical Director of Diet Doctor, raises in his analysis of the January 2022 publication of the 450-page Cochrane Review of randomized trials of low-carb diets.
When it comes to evaluating medical research, Cochrane reviews usually have a reputation for being unbiased, independent, and reliable. But not this time. "The bias is apparent, even in their title," says Dr. Scher.
Cochrane: Low-carbohydrate diets or balanced-carbohydrate diets: which works better for weight loss and heart disease risks?In his DDNews video, Dr. Scher points out that the use of the word "balanced" for higher-carb diets is a "very judgemental term" implying that lower carb diets are somehow "unbalanced."
Get your personalized meal plan with a FREE 30-day trial!
Dr. Scher highlights a number of other problems with the Cochrane systematic review, including that once again they do not focus on truly low-carb diets, and they make sweeping conclusions that don't apply to true low-carb eating.
In fact, of the 47 randomized control trials they review, only 11 - or less than a quarter - could be classified as low-carb diets. The remaining diets had fewer carbs than conventional diets, but did not reduce carbs to 10% of energy to qualify as true low-carb diets.
"If you're going to combine them [truly low-carb diets and other diets with as much as 45% of calories from carbohydrates], and make a data analysis, based on all the studies combined, you're comparing apples and oranges," says Dr. Scher. "You cannot combine them."
Another problem with the review is that the majority of the studies were designed to provide the same calorie count between the lower carb or higher carb arms. (This is also called isocaloric diets by researchers.)
Dr. Scher points out that this effectively eliminates one of the known benefits of low-carb eating: eating fewer calories without counting calories.
"Studies show, time and time again, with low carb eating, the average participant will naturally reduce their caloric intake. Even without telling them to do so, they lower their calories because they're more satiated," said Dr. Scher.
In his video analysis, Dr. Scher finds other weaknesses of the Cochrane review. On a more positive note, Dr. Scher does highlight one advance in this mainstream analysis: a low-carb diet is being found to be as effective as any other diet and should therefore be "one of the tools in the toolkit" offered to patients to lose weight or improve their metabolic syndrome.
"For me, I think the biggest message is that low-carb diets work. They work as well as other diets. They work in the right setting for the right people," he said. "So they should clearly be part of every clinician's offerings, whether physician, nurse practitioner, dietitian, health coach - anyone giving nutritional advice."
Each week, Dr. Scher creates two or three videos that review relevant or interesting scientific studies in the fields of nutrition, exercise, health, or disease and carefully analyses the researchers' methods and findings. In doing so, he helps you better understand how to judge the quality of various research papers and make informed decisions about your own health and wellness.
You can find more of Dr. Scher's news videos on the Diet Doctor Youtube Channel. Subscribe to the feed so that you don't miss any of his videos.