February 7, 2024 – Atkins, Keto, the Zone, the Paleo diet – it seems like low-carb diets have been around forever and have been gaining popularity over the years. However, despite their fame, it remains unclear what exactly „Low Carb“ really means.
A study recently published in Critical Reviews in Food Science and Nutrition analyzed over 500 articles on low-carb diets and found that there is still a real discrepancy within the scientific community about what „low carb“ means.
The lead researcher of the study, Taylor Wallace, PhD, CEO of the Think Healthy Group and adjunct professor of nutrition and food studies at George Mason University, said that it is striking that given the amount of research put into studying low-carb diets, we still do not have a clear definition.
The range of studies evaluated – all published between 2002 and 2022 – found that most studies defined low-carb as consuming 100 grams or less of carbohydrates per day. However, many also had much stricter definitions, with carbohydrates making up only 40–60 grams per day.
The variability, Wallace said, should underscore the fact that low-carb diets may not be suitable for everyone. „There is a lot of data showing that low-carb diets work for diabetes and weight loss,“ said Wallace. „But I also think there is a lot we don’t know, and we shouldn’t overstate it: ‚Eat as much saturated fat as you want, it doesn’t matter as long as you eat low carb.‘ That’s a bit out there.“
The other issue Wallace pointed out was that most studies did not follow up with participants beyond the 6-month mark, providing no insight into the long-term sustainability of these dietary plans.
For example, a systematic review and meta-analysis published in the journal BMJ in 2021 found that low-carb diets increased remission rates in people with type 2 diabetes who adhered to them for six months. However, the same study found that the benefits of the diet significantly declined after 12 months, and participants‘ LDL cholesterol levels worsened.
The first recommended daily intake set in 2002 by the Institute of Medicine stated that both children and adults should consume at least 130 grams of carbohydrates per day for brain function and health.
Given the popularity of diets like Keto and Atkins, which typically restrict carbohydrate intake to less than the recommended daily intake, focusing on the long-term adherence to the diet is crucial for understanding overall health outcomes that go beyond just shedding pounds on the scale.
„We just need to be cognizant that we don’t have the literature to say what potential long-term effects adhering to a carbohydrate diet of less than 130 grams per day could have,“ said Katrina Hartog, a registered dietitian and nutrition scientist at New York University.
It is also important to keep safety concerns in mind, even if one falls into the category of people who could benefit from a low-carb diet, said Hartog. Malnutrition, disordered eating, muscle mass decline – all of these should be a significant part of low-carb research, and these events can only be properly evaluated after the 6-month mark.
Wallace said that the findings of his study should prompt further research. In particular, he would like to see a systematic review to truly synthesize the results of the many studies we already have.
„If everyone is calling ‚low carb‘ something different, research will never give us an answer because all studies are different,“ said Wallace. „If we want to move forward in this area, we need to decide what ‚low carb‘ is.“