Low-Carb vs. No-Carb Diets

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People considering a carb controlled diet often wonder about the differences between low-carbohydrate and no-carbohydrate diets. While the underlying principles are the same, the implementation is different. How do low-carb diets stack up against no-carb diets?

History and Principles

Many low-carbohydrate diet proponents believe human beings need to avoid refined carbohydrates, sugars, and processed foods as an evolutionary imperative. Early humans were hunter-gatherers who most likely ate foods they could either forage or kill. Some physicians, like Kurt G. Harris who invented the Archevore Diet, suggest the human body has not evolved to process Western foods, such as processed foods like pasta, baked goods, and sugary snacks. Low-carbohydrate diets that focus on animal protein and vegetables mimic the eating habits of early humans, possibly providing a healthy, more natural way of eating.

In his book, Good Calories, Bad Calories, Gary Taubes explains how carbohydrate consumption affects humans. When you eat carbohydrate-containing foods, blood glucose rises. In response, your pancreas releases insulin to return blood sugar to a normal level. This is a normal regulatory process. However, when carbohydrates are in excess, insulin stores them in fat cells and keeps that fat from leaving the cells. Why does insulin do this? Because it exists to protect your body from times of famine by storing energy for lean times. Both types of diets limit producing excessive insulin.

Low-Carb Diets vs. No-Carb Diets: What's the Difference?

Low-carb and no-carb diets seem similar, but they are drastically different and elicit different responses in the body.

Low-Carb Diet - What You Eat

The Mayo Clinic classifies diets consisting of 20-60 grams of carbohydrates per day as low-carb. Low-carbohydrate diets typically result in some weight loss. These diets allow consumption of some carbohydrate-containing foods such as:

  • Non-starchy vegetables like celery, lettuce, kale, cabbage, zucchini, and cucumbers
  • Nuts
  • Moderate to low carbohydrate fruits like watermelon, berries, cantaloupe, peaches, and honeydew

Programs like Atkins, Protein Power, and South Beach, follow a low-carbohydrate protocol. Additionally, recent research investigates a low carbohydrate, high fat diet known as a ketogenic diet. In this diet, carbohydrate intake is less than 20g/day, forcing the body turn to an alternative form of fuel known as ketones. Studies suggest the body can function and certain health conditions can improve on a ketogenic diet. However, the research is lacking in the long-term effect of the diet.

No-Carb Diet - What You Eat

In contrast, a no-carb diet consists of zero carbohydrates. So while with a low-carb diet you may eat fruits, nuts, seeds, and veggies, these are off the table if you're eating zero carbs. Instead, you eat animal protein and fat. There are no know no-carb programs to date. People may assume following a zero carbohydrate diet will bring about faster and greater losses than a low-carb diet. However, there is no scientific evidence that eating a zero carbohydrate diet will lead to greater weight loss.

Low-Carb Studies

Low-carbohydrate diets have been studied to determine their efficacy. A 2010 Temple University study followed dieters for two years. One group of participants ate a traditional low-fat, low-calorie diet while another group ate an Atkins-style low-carbohydrate diet. The study showed both diets to be equally effective at generating weight loss. Similar results have turned up in other studies, as well. Additionally, clinical reviews show other potential health benefits of low-carb diets, such as improved glycemic control and reduced risk of cardiovascular disease.

Studies on the ketogenic diet demonstrate improvement in epileptic children, adolescents, and adults and potential benefits in metabolic syndrome and diabetes.

No-Carb Studies

Studies conducted on no-carb diets are lacking as it may be unethical to place a human on this diet. One study on a zero-carbohydrate diet occurred in 1929 when two men agreed to go a year eating only meat. The study participants did not lose weight, but they also did not experience any noted adverse effects.


Some health experts express concern that low-carbohydrate diets contain insufficient fiber, which can lead to constipation or even colon disease. No-carb diets contain even less fiber. Both low and no-carb diets can be high in saturated fat, which has been shown to contribute to heart disease.

Moderation for Sustainability and Safety

No-carbohydrate diets are an extreme form of low-carbohydrate diets. For many, they prove difficult to maintain due to a lack of variety in the diet and low energy levels. Most experts suggest a moderate approach to low-carbohydrate dieting that includes, at the very least, fruits and non-starchy vegetables. No discernible benefits arise from fully limiting carbohydrates. Before going on a low-carbohydrate or no-carbohydrate diet, speak with your health care provider.

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Low-Carb vs. No-Carb Diets