The number of carbs allowed on a low-carb diet is highly variable and depends, in part, on your dietary needs. Following a very low-carb ketogenic diet significantly limits daily carbs, while a generic low-carb diet can include enough carbs to meet the recommended dietary allowance. Even though the U.S. Department of Agriculture hasn’t yet established precise definitions for the daily low-carb allowance, experts in the field offer guidelines you can use to develop the low-carb plan that fits your needs. For a personalized plan, consult a registered dietitian.
The Number of Carbs in a Low-Carb Diet
The term “low-carb diet” doesn’t have a legal definition, which results in diverse interpretations. For example, the Atkins Diet begins at 20 to 50 grams of carbs daily in Phase I, then allows 75 to 100 grams in later phases. In 2008, the American Diabetes Association defined a low-carb diet as one that has fewer than 130 grams daily, according to a report in Nutrition and Metabolism. More recent studies exploring low-carb diets provide 30 to 100 grams of carbs daily.
By comparison, the Institute of Medicine recommends that you get 45 to 65 percent of your daily calories from carbs, and has set the recommended dietary allowance for carbohydrate at 130 grams daily. Consuming fewer than 20 grams of carbs daily is known as a ketogenic diet, or a very low-carb diet. The brain only uses glucose or ketone bodies for energy. When you restrict your glucose intake due to a low carb intake, your body converts fats into ketone bodies. A ketogenic diet is successful for weight loss, but for a low-carb diet that doesn’t go into ketosis, keep your carbs between 70 grams and 130 grams.
The Effectiveness of a Low-Carb Diet
Researchers have compared the success of low-carb and low-fat diets. Structured programs such as Atkins, Zone, LEARN and Ornish -- which range from very low-carb to very high-carb diets -- have also been evaluated. In the end, any diet that includes fewer calories consumed than burned results in meaningful weight loss -- no matter which combination of macronutrients is preferred -- reports the Harvard School of Public Health. An overall concern when you lose weight following any restrictive diet is whether or not you’ll regain the weight when you return to consuming the recommended amount of carbohydrate in your diet.
Low-carb diets improve your health by decreasing the amount of new fats being synthesized. They also help lower blood levels of triglycerides and total cholesterol, while increasing good cholesterol, according to a review in the International Journal of Environmental Research and Public Health in February 2014. A low-carb diet with high protein further supports weight loss as protein boosts satiety. If you follow a ketogenic diet, you'll get the same benefits and you'll lose weight more rapidly as long as calories are restricted. Ketogenic diets may be dangerous for people with kidney disease -- and they may cause loss of bone density -- so talk to your doctor to be sure it's safe for your health.
Tracking the Number of Carbs Consumed
When you decide to follow a low-carb diet, you’ll need a plan for tracking the amount of carbs you eat to be sure you stay within your daily goal. Since carb counting is essential for people with diabetes, one approach already exists that will make your task easier. The exchange system categorizes foods based on their carb, protein and calorie content. This system provides lists of foods that all have a similar number of carbs, so you can use that number to easily tally your intake. The list also tells the portion size -- which is really important -- to be sure your portions don’t contribute too many carbs or calories. For example, fruits have 15 grams of carbs, but only if you don't eat more than 1/2 cup of fresh fruit, reports the University of Arkansas.
If you want to be very specific about your carb intake, use the amount of total carbohydrates listed in the nutrition facts label. Once again, be sure to compare your portion to the serving size so you calculate the right amount of carbs. The label can also be used to determine the net carbs, which is the total amount of carbohydrates minus dietary fiber and sugar alcohols. The American Diabetes Association suggests three steps for calculating net carbs. Sugar alcohols don't have to be included on the label -- but if they are and if the amount is greater than 5 grams -- subtract half the grams from total carbs. If insoluble fiber is reported, subtract the entire amount. Finally, subtract half the remaining grams of fiber from total carbs, but only if the remainder is greater than 5 grams.
Low-Carb Choices for Weight Loss
Some people follow a low-carb diet for health reasons, such as diabetics who need to manage blood sugar or those who follow a ketogenic diet to treat epilepsy. If you’re using low-carbs to lose weight, you’ll need to focus on low-carb foods that don’t blow your daily calorie budget. Meat, fish and eggs have zero carbs, but calories range from 35 calories per ounce in very lean choices, such as fish, egg whites and poultry white meat without skin, to 100 calories per ounce in high-fat proteins, which includes cheese and lunch meat. Other types of protein such as beef, pork and poultry dark meat, contain 55 to 75 calories in an ounce, according to the exchange list.
Reducing calories and carbs increases the risk of not getting all the nutrients your body needs or not having enough energy to stay active. Maximize your energy by dividing the total daily carbs and fats equally between meals. Don’t waste calories or deplete your carb allowance with processed foods and products that have added sugar. Give top priority to a variety of vegetables, which provide vitamins, minerals, fiber and phytonutrients. One cup of raw vegetables and 1/2 cup of cooked vegetables supplies 5 grams of carbs and 25 calories. Beans, whole grains and starchy veggies, such as potatoes, peas and corn, have about 15 grams of carbs and 80 calories per serving. Fruits also contain 15 grams of carbs, but a serving only has 60 calories.
- University of Louisville School of Medicine: Low-Carb Diets
- Nutrition and Metabolism: Dietary Carbohydrate Restriction in Type 2 Diabetes Mellitus and Metabolic Syndrome: Time for a Critical Appraisal
- Today’s Dietitian: Low-Carb Diets -- Research Shows They May Be More Beneficial Than Other Dietary Patterns
- Institute of Medicine: Dietary Reference Intakes: Macronutrients
- Internal Medicine: A Non-Calorie-Restricted Low-Carbohydrate Diet Is Effective as an Alternative Therapy for Patients With Type 2 Diabetes
- Harvard School of Public Health: The Best Diet: Quality Counts
- International Journal of Environmental Research and Public Health: Ketogenic Diet for Obesity: Friend or Foe?
- University of Arkansas: The Exchange List System for Diabetic Meal Planning
- Diabetes Forecast: What Are Net Carbs?