What Is a Low-carb Diet?

A low-carb diet emphasizes eating proteins, natural fats, and vegetables, while decreasing, and in some cases eliminating altogether, the consumption of grains, breads, pastas, rice, starchy root vegetables, refined and processed carbohydrates, and sugar-sweetened beverages. There are generally no restrictions or limitations placed on the intake of proteins and natural fats other than to “eat to satiety.”

There are many variations of a low-carb diet, but in general it can be divided into three categories based on the amount of carbohydrates consumed per day:

• Strict: 0-20 grams/day
• Moderate: 20-50 grams/day
• Liberal: 50-100 grams/day

To put this into perspective, the average American diet consists of approximately 50% carbohydrates.¹ Therefore, an individual who eats a 2,000-calorie-per-day diet will consume 250 grams of carbohydrates per day. (50% of 2,000 calories = 1,000 calories from carbohydrates; there are four calories per one gram of carbohydrate, so 1,000/4 = 250 grams of carbohydrates per day.) Depending on the individual patient, daily carbohydrate intake may be significantly higher than the 250 gram/day average.

Of the three main macronutrients—protein, fat, and carbohydrates—it is the ingestion of carbohydrates that induces the secretion of insulin the most. Carbohydrates ultimately break down into simple sugars and glucose in the digestive tract, and are then transported throughout the body to be used as energy. Under the direction of insulin, any excess glucose, beyond that which is needed for bodily functions, is converted into fat and stored in adipose tissue. Lowering the amount of carbohydrates eaten lowers the amount of insulin secreted. It is this decrease in the amount of circulating insulin that decreases body fat storage and increases utilization of stored body fat, while at the same time helping to slow the progression of diseases such as type 2 diabetes, hypertension, and some cancers. Low-carbohydrate diets have also been shown to decrease triglyceride levels and increase HDL levels.²

The key component of a low-carb diet is the restriction or elimination of sugars; foods with added sugars; sugar-sweetened beverages; and highly refined, processed carbohydrate foods, such as processed flours, grains, bread, rice, pasta, pastries, “convenience” foods, snacks, and starchy root vegetables; and to replace them with lower-carbohydrate, fiber-rich vegetables, such as leafy greens and cruciferous vegetables. The amount and types of carbohydrates consumed can be tailored to the individual patient depending on the goals they would like to achieve.

Patients with obesity and type 2 diabetes may require a more restricted carbohydrate gram-per-day count compared to a patient who has obesity but not any other medical conditions. It is this personalization that can help provide significant weight reduction and improved management of insulin-resistance-related disorders. In both cases, the consumption of protein and natural fats are not limited, but their intake should not exceed the patient’s level of satiety.

For more information regarding low-carbohydrate diets, check out the nutrition presentations available in the Obesity Medicine Academy.