CARBS: HOW LOW IS LOW?

Everyone says "low carb," but they don't always mean the same thing. Ask ten people what counts as low carb, and you'll likely get ten different carbohydrate cut-offs. This isn't just confusing for the average consumer = it's made it genuinely difficult for researchers to evaluate the efficacy of lower-carbohydrate interventions, since "low carb" in one study might look nothing like "low carb" in another.

There's still no single, official definition of what constitutes a low-carbohydrate diet. That said, many recent definitions are converging around 130 g/day of total carbohydrates or less. Factor in the recommended 30-40 grams of fiber per day, and that lands you at roughly 90-100 grams of net carbs—right in line with the philosophy behind ‘Just the right amount of Atkins’.

This is in line with a recent expert consensus paper which proposes that very-low carbohydrate/high-fat ketogenic diets consist of <10% energy from carbohydrate or 20-50 g/day and low-carbohydrate diets consist of 10-25% of energy from carbohydrate or 50-129 g/day. When you consider the fact that Americans eat around 250-300 grams of carbohydrates per day or about 40-50% of their calories come from carbohydrates, this represents a substantial reduction in carbohydrates and really helps cut-out a lot of the refined carbs and added sugars that are so prevalent in the Standard American Diet.

The 130-gram number isn't arbitrary — it ties back to the brain's approximate glucose needs which determines the “Recommended Dietary Allowance” for carbohydrates in the dietary reference intake framework used by the United States government to inform portions of U.S. dietary policy.

Once intake drops below 130 grams per day, the body prioritizes whatever glucose is available for the brain, forcing most of the other tissues in the body to shift toward relying on fat and/or ketones for energy. Essentially dropping below this threshold triggers a metabolic shift. This becomes even more pronounced at very low levels of carbohydrate intakes seen in ketogenic diets.

Defining low-carbohydrate diets as containing less than 130 grams of total carbohydrate, or <25-26% of energy, has been useful for evaluating research on low-carbohydrate interventions. A few key studies are particularly relevant here, showing that this level of carbohydrate restriction has distinct effects on metabolism and/or blood sugar levels.

Published in The BMJ in 2018, one study set out to answer a hotly debated question: how do diets varying in their carbohydrate-to-fat ratio affect metabolism? Researchers took 164 adults with overweight or obesity and first had them lose about 12% of their body weight. They were then randomly assigned to one of three test diets — high (60% of calories from carbs), moderate (40% of calories), or low (20% of calories, or about 100 grams of carbs per day at 2000 calories/d) - for 20 weeks, with each diet adjusted to keep weight stable. The key finding: lowering dietary carbs altered metabolism and energy expenditure during weight-loss maintenance — while far from definitive, this suggests there is a metabolic effect that may help people keep weight off.

Another study, also published in The BMJ, evaluated the body of literature that has already been published around low-carbohydrate diets and diabetes. In what's known as a meta-analysis, the researchers assessed the efficacy of different low-carbohydrate diets for supporting healthy blood sugar regulation in people with type 2 diabetes. The authors concluded that at 6 months, of all the interventions tested, the more restrictive very-low-carbohydrate diets (<10% of calories from carbohydrate) were less effective than the more moderate low-carbohydrate diets (defined as 10-<26% of calories from carbohydrate) — largely because adherence was better on the moderate approach. My interpretation: Allowing for a little more flexibility can really help improve how easy it is to stick with your low-carb approach.

We've always said that Atkins is low carb, not no carb, and we're now seeing a growing body of published research showing that even more moderate levels of carbohydrate restriction can meaningfully improve multiple aspects of metabolic health. With this mindset, success becomes less about eliminating carbohydrate-containing foods altogether and more about being intentional with portions, while limiting excess calories from refined grains and added sugars.

We also recognize that food is deeply connected to culture, family traditions, and personal preference. For many people, completely giving up their favorite meals isn't realistic or necessary - at least according to research. Instead, choosing your battles carefully and making thoughtful adjustments can still lead to meaningful health improvements. In fact, many studies demonstrating benefits with carbohydrate intakes around the ~100 net carb range have been conducted in regions such as Asia and Europe, where carbohydrate-rich foods are dietary staples. These findings show that foods like rice, pasta, and bread can still fit into a lower-carbohydrate lifestyle when portions are managed appropriately, low glycemic carbs are prioritized, and overall carbohydrate intake is kept in check.

Everyone processes food in a different way, depending on age, sex, body composition and overall health. When you limit your carbs and consume more tailored amounts of protein, nutrient-rich vegetables, low-glycemic fruits and healthy fats, you help guide your metabolism—and ultimately, what types of fuel your body uses for energy.