Low-Carb and No-Carb Diets: What They Get Right and What They Miss
Low-Carb and No-Carb Diets: What They Get Right and What They Miss
Low-carb and no-carb diets have been around for decades, cycling in and out of popularity under different names and marketing angles. While they are often framed as a clear solution to weight loss, blood sugar control, or “metabolic health,” there is no single, agreed-upon definition of what a low-carb diet actually is. That lack of definition alone creates a lot of confusion.
For some people, “low carb” means cutting out bread, rice, pasta, and potatoes. For others, it includes avoiding fruit. Some go further and eliminate most plant foods entirely. Others are counting grams and aiming for a specific number. And sometimes, when I talk with people about their intake, what they call low carb is actually very much within standard nutrition recommendations.
What Does “Low Carb” Actually Mean?
From a nutrition science standpoint, carbohydrates are one of the three macronutrients, along with protein and fat. The Acceptable Macronutrient Distribution Range, or AMDR, provides evidence-based ranges for how much of total calorie intake should come from each macronutrient for overall health.
For carbohydrates, the AMDR is 45-65% of total calories. Protein is 10 to 35%. Fat is 20 to 35%. I must remind people that these are ranges. It is not recommended that everyone have 65% carbs, 35% protein, and 35% fat, for one, because that would exceed 100%, which isn’t possible. Two, we don’t eat the same each day, so these percentages vary day to day. And three, these ranges are tweaked to fit into an individual’s personal needs. For example, I may recommend about 50% carbs, 30% fat, and 20% protein, but I really calculate protein needs by body weight and then back into the other numbers…let’s just say, I do a lot of math and recalculations in my work. A lot.
That higher end of the carbohydrate range is generally intended for people who are very physically active, such as endurance athletes or individuals with physically demanding jobs, who need consistent glycogen replenishment. Someone eating closer to the middle of that range, around 50 percent of calories from carbohydrates, is still well within evidence-based guidelines. But in a given week, even that endurance athlete may have a lower percentage on rest days.
Using a 2,000-calorie diet as an example only, not as a recommendation, 50 percent of calories from carbohydrates equals about 1,000 calories, or about 250 grams per day. That surprises many people who have been told that the number is excessive, when in reality it falls squarely within established recommendations for many adults. Keeping in mind that carbs are in more than just grains and starchy foods.
Read more: What Are Carbohydrates? Fiber, Starch, and Sugar Explained
When Low Carb Becomes Very Low
Some people intentionally aim for fewer than 100 grams of carbohydrates per day. Using that same 2,000-calorie example, 100 grams of carbohydrate provides 400 calories, or about 20 percent of total intake. That is well below the AMDR.
Others go lower still, targeting 50, 30, or even 20 grams per day. Often this is calculated using “net carbs,” a concept discussed previously, which is not a recognized category in nutrition science.
Read more: What Are Net Carbs and Do They Actually Matter?
It is important to note that the minimum recommended carbohydrate intake is 130 grams per day. This amount is based solely on the brain’s glucose needs. Consistently eating below that level means the body must rely more heavily on alternative pathways (which require protein breakdown) to meet basic energy needs, with consequences.
Then there are carnivore-style diets that eliminate carbohydrates almost entirely. Those patterns deserve a separate, detailed discussion and fall outside the scope of this post. And, really, I don’t even want to bother since that’s more of a cult than a diet. It seems they are adamant that fiber is wholly unnecessary, so I’ll let them and their risk of colon cancer alone.
What Does It Mean When People Say Low Carb “Worked”?
Really, I must know. I see this often: “Low carb worked for me.” When someone says a low-carb diet worked for them, it is worth pausing to ask what that means. Often, I assume, it means weight loss. But I do check in and don’t always assume because, less commonly, it may refer to short-term changes in blood sugar or appetite.
Weight loss on a low-carb diet is not surprising. Reducing carbohydrates leads to rapid depletion of glycogen stores in the liver and muscles. Each gram of glycogen is stored with several grams of water, so when glycogen is depleted, water weight drops quickly. This is not fat loss (which is physiologically impossible at that rate), but it shows up on the scale immediately.
Calorie intake also tends to drop when entire food groups are removed. Fewer food choices usually mean fewer calories, at least in the short term. But also, if people were relying heavily on overly processed, higher-carbohydrate foods and stopped eating them, what do they think will happen? Weight loss is highly likely.
The “problem” is what happens next. When carbohydrates are reintroduced, glycogen and water stores are replenished, and weight returns just as quickly. This cycle often leads people to believe carbohydrates are the problem, when the real issue is the unsustainable nature of the restriction. So, not the carbohydrates directly.
Blood Sugar, Monitoring, and Misconceptions
Low-carb diets are sometimes promoted for blood sugar control. For people with diabetes, carbohydrate timing, quality, and quantity do matter, but diabetes management is not simply about eating as few carbs as possible. Eliminating carbohydrates entirely is not the standard of care. Never – and it won’t reverse diabetes.
For individuals without diabetes or prediabetes, frequent glucose monitoring is unnecessary. Checking blood sugar more than annually in otherwise healthy individuals rarely provides useful information and often increases anxiety and obsession with their food intake, rather than insight.
Short-Term Appeal vs Long-Term Reality
In the short term, low-carb diets can reduce appetite, simplify food decisions, and lead to quick weight changes (loss). That can feel motivating.
Long-term, sustainability becomes the issue: how long can you keep doing it? Forever? Or only until your vacation. Diets that eliminate fruits, whole grains, beans, and many vegetables remove major sources of fiber, vitamins, minerals, and phytonutrients. And, seriously, the known benefits of fruits, vegetables, and whole grains are massive and supported by decades of research. Population and longevity research show that there is no known harm in consuming the recommended daily amount of fruits and vegetables.
Diets that significantly reduce fruits, vegetables, whole grains, and beans can negatively impact gut health and make social eating more difficult. Though I have met people who don’t care to eat socially and are okay with not eating at restaurants, except for salads and meat. Try visiting another country and see how that goes.
Some people may benefit temporarily from a lower-carb approach, particularly under medical supervision. Others struggle significantly, experiencing fatigue, digestive issues, irritability, or intense cravings. There is no universal response.
What Low-Carb Diets Get Right
Low-carb approaches often encourage people to reduce intake of refined carbohydrates and added sugars. That part aligns with established nutrition guidance.
They may also increase awareness of protein intake and emphasize minimally processed foods. These are not inherently bad outcomes. We need adequate protein just as much as carbohydrates and fiber-rich foods.
What They Miss
Where low-carb diets fall short is in their approach to carbohydrates as a single category rather than a diverse group of foods with very different nutritional profiles – remember that carbohydrates are a nutrient, not a food group. Fruits, vegetables, whole grains, beans, lentils, nuts, and seeds are not interchangeable with cookies and soda.
Carbohydrates are the body’s preferred energy source. They fuel the brain, muscles, and red blood cells. Removing them entirely ignores basic human physiology.
A More Practical Approach to Choosing Balance Carbs (for Non-Athletes)
For most non-athletes, the goal does not need to be low-carb or high-carb. It needs to be balanced and consistent.
Do not cut out fruits and vegetables. They provide fiber, antioxidants, and nutrients that support long-term health.
Include whole grains. They provide sustained energy and support gut and cardiovascular health.
Use beans, lentils, and legumes regularly. They provide carbohydrates, protein, and fiber together, which helps stabilize blood sugar.
Include nuts and seeds for healthy fats, fiber, and micronutrients.
If weight loss or blood sugar management is a goal, focus on portion size, overall calorie intake, and food quality rather than eliminating an entire macronutrient.
Balance matters. Consistency matters. And sustainable habits matter far more than how low your carb count goes on paper.
Next up: Carbohydrates, Sugar, Fiber, and Chronic Disease
Related blogs in this series:
Carbohydrates vs Sugar: What’s the Difference and Why It Matters
The Six Essential Nutrients Explained: A Foundational Guide to Nutrition
What Are Carbohydrates? Fiber, Starch, and Sugar Explained
Fiber 101: Soluble, Insoluble, Functional Fiber, and Resistant Starch
What Are Net Carbs and Do They Actually Matter?
