Interest in low-carbohydrate diets continues to grow around the world. In fact, the popularity of these low diets has doubled among American consumers over the past decade. However, despite the eating pattern’s popularity, confusion remains over what exactly is considered a low-carb lifestyle.
Now, a scoping review from the Friedman School of Nutrition Science and Policy at Tufts University (USA), published in Critical Reviews in Food Science and Nutrition, sheds new light on the topic and suggests that it is generating a scientific consensus around the term. Of the more than 500 clinical trials reviewed, the majority defined a low-carbohydrate diet as limiting carbohydrate intake to 30% or less of total calories or eating less than 100 grams of carbohydrates per day. The review included results from a total of 508 clinical studies published between 2002 and 2022, more than half of which were randomized controlled trials and almost a third were government-funded.
“The sheer volume of clinical trials on low-carbohydrate diets published over the past two decades was surprising. Any perception that there is a lack of scientific evidence on low-carbohydrate eating patterns, or even a lack of government-funded evidence at clearly not supported by the data,” says lead researcher Dr. Taylor Wallace.
The review also found that 152 of the studies included in the analysis were designed to evaluate the effect of a low-carbohydrate diet on weight or body composition. Notably, these studies are often excluded from consideration in various federal nutrition evidence review processes, such as updates to the Dietary Reference Intake (DRI) guidelines for carbohydrates and the Dietary Guidelines for the Evaluation of Low-Carbohydrate Dietary Patterns. carbohydrates of Americans.
These guidelines serve as the basis for numerous public health and nutrition activities, including food and nutrition labeling, federal nutrition programs, patient counseling, and public health education initiatives. Additionally, the researchers noted key gaps in the published literature.
Although most studies classified low-carbohydrate diets as consuming 30% or less of total calories from carbohydrates or limiting carbohydrate intake to less than 100 grams per day, the findings also revealed discrepancies.
Of the studies that used the percentage of total calories as a parameter to define a low-carbohydrate diet, the percentages ranged from zero to 50% of total calories coming from carbohydrates. And, of the studies that define “low carb” by the number of grams of carbohydrates consumed daily, many used thresholds well below 100 grams per day.
“As both consumers and public health officials are interested in understanding the potential benefits of low-carbohydrate eating patterns, reaching a standardized consensus definition is non-negotiable and urgently needed,” Wallace says. The researchers note that systematic reviews and dose-response meta-regressions using patient-level data on carbohydrate intake, status markers, and health are key next steps to inform a clear, consistent, and widely adopted definition of the term “low carb.”
