February 7, 2024 – Atkins, keto, the zone, the paleo food regimen – it looks as if low-carb diets have been around endlessly, and have only grown in popularity through the years. But despite their fame, it stays 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 located that there stays an actual discrepancy within the scientific community about what “low-carb” means.
The study's principal investigator, Taylor Wallace, PhD, CEO of Think Healthy Group and associate professor of nutrition and food studies at George Mason University, said that is striking given the quantity of research that has gone into studying low-carb diets we don't have a transparent definition.
The series of studies reviewed – all published between 2002 and 2022 – found that almost all studies defined low carb as consuming 100 grams or fewer carbohydrates per day. But many also had much stricter definitions, with carbohydrates only accounting for 40-60 grams per day.
The variability, Wallace said, should underscore the undeniable fact that low-carb diets will not be right for everybody.
“There is a lot of data showing that low-carb diets work for diabetes and weight loss,” Wallace said. “But I also think there's a lot we don't know, and we shouldn't exaggerate: 'Eat as much saturated fat as you want, it doesn't matter as long as you eat a low-carb diet.' .' That's a bit too far fetched for me.
The other problem Wallace pointed out was that most studies didn't follow participants beyond the 6-month time point, which doesn't provide any insight into how sustainable these eating plans are in the long term.
A scientific review and meta-analysis published from the magazine BMJ For example, in 2021, low-carb diets in people with type 2 diabetes were found to increase remission rates in those who stuck with them for six months. However, the same research found that the diet's benefits had diminished significantly after 12 months and participants' LDL cholesterol levels had worsened.
The first recommended daily allowance, set by the Institute of Medicine in 2002, said 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 such as keto and Atkins, which typically limit carbohydrate intake to less than the recommended daily allowance, focusing on long-term adherence to the diet is critical to understanding the overall health outcomes that occur across diets the pounds lost on the scale.
“We just must be aware that we don't have the literature to say what the potential long-term consequences of following a carbohydrate food regimen of lower than 130 grams per day may be,” said Katrina Hartog, a registered dietitian. Nutritionist at New York University.
It's also important to keep safety concerns in mind, even if you're in the category of people who could benefit from a low-carb diet, Hartog said. Malnutrition, disordered eating habits, loss of muscle mass – all of these should be an essential part of low-carb research. And these events can only be properly evaluated after the 6-month mark has passed.
Wallace said the results of his study should prompt further research. In particular, he would like to see a systematic review to really summarize the results of the many studies we already have.
“If everyone calls 'low carb' something different, research won’t ever give us a solution because all studies are different,” Wallace said. “If we intend to make progress on this area, we’d like to make your mind up what 'low-carb' is.”