An array of diets are based on the idea that slashing carbohydrates is the key to weight loss. For example, the keto diet emphasizes eating fats, with the goal of putting your body in the state of ketosis. In ketosis, the body breaks down dietary and stored body fat into substances known as ketones. In this state, your body relies on – and burns – fat instead of sugar for energy. Keto regimens call for consuming as few as 50 to 20 grams of carbs a day, depending on the particular diet.
That's a far lower amount than what's recommended by the 2020-2025 Dietary Guidelines for Americans. Those guidelines recommend that carbs comprise between 45% and 65% of your total daily calories. That means if you consume, say, 2,000 calories on a daily basis, between 900 and 1,300 calories should come from carbs. That would mean you're consuming 225 to 325 grams of carbs.
While similar in some ways to familiar low-carb diets, the keto diet's extreme carb restrictions and the deliberate shift into ketosis are what set this increasingly popular diet apart. Keto diets typically never go above 50 grams of carbs per day, and you can get that by eating two apples or one bagel. (Some experts say the keto diet can be effective for rapid weight loss but is associated with adverse effects, like nausea and constipation.)
The keto diet (and other low-carb regimens) are based on the premise that to lose weight, you need to cut carbs. And while there's no one universally accepted definition for going low-carb, one Tulane University review (that concluded low-carb diets are beneficial both for weight loss and improving cardiovascular health) defines low-carb diets as those in which less than 45% of daily calories come from carbohydrates. Based on a 2,000-calorie diet, that would mean eating no more than 900 calories from carbs (that's 225 grams) per day. (Each gram of carbs contains 4 calories.)
So how low do you really need to go to lose weight? Or, more importantly, how many carbs can you keep in your diet and still lose weight? Because what's a life without pasta?
Along with protein and fat, carbohydrates are one of the three macronutrients that you need to consume in order for your body to function at its best. It's important to get these macronutrients in the right amount.
Carbs are an important fuel for your brain, liver, and muscles. Those tissues can use fat and protein (muscle) for energy instead.
However, using only fat and protein is a less efficient metabolic process that can contribute to an array of symptoms, explains Donald K. Layman, professor emeritus of food science and human nutrition at the University of Illinois.
These symptoms include:
It's important to keep in mind there are two different groups of carbohydrates, says Anthony DiMarino, a registered dietitian with Cleveland Clinic's Center for Human Nutrition.
You can get complex carbohydrates from:
Whole grains (brown rice, whole-wheat bread).
You can also find carbohydrates in processed foods that provide simple sugars, DiMarino says.
These foods include:
Some complex carbs, like fruits and vegetables that are high in fiber and low in simple sugars (apples and berries, for example), are associated with a slower rate of digestion, Layman says. A slower rate of digestion reduces the post-meal blood sugar increase and the body's requirement for insulin. Generally, eating the right complex carbs is helpful for those concerned about diabetes and their weight.
Carbs with simple sugars may be pleasurable to eat, but provide little or no nutritional value other than calories.
In recent years, carbohydrates have gotten a bad rap for the part they play in blood-sugar-spiking snacks and sugary drinks notes Florida-based registered dietitian Jaime Mass.
"Most of the time, we are eating carbohydrates from the wrong sources. And when we do eat from the healthier sources, we overdo it," Mass says.
Be aware that carbs can add up quickly, DiMarino says. For instance, a standard serving of carbs is defined as 15 grams. Two cups of brown rice – which can be a completely healthy and nutrient-packed carb choice, weighs in at 90 grams – equal six servings. At the end of the day, the average American consumes nearly three times the recommended daily allowance of carbs.
How Many Do You Really Need?
The current recommended daily allowance, or RDA, of carbohydrates, is 130 grams per day. That total represents the minimum rather than optimal daily intake and covers the amount your brain and liver need for prime functioning, plus a little extra for your muscles and good measure.
Introduce exercise into your routine, though, and your needs begin to vary widely. That's because when you exercise at high intensities, about 80% of your energy comes from carbohydrates – both those coursing through your bloodstream as glucose as well as those stored in your liver and muscles as glycogen.
During intense exercise, your body burns through roughly 60 grams of carbohydrates per hour, Layman explains. And, according to research published in Sports Medicine, carbohydrate supplementation can significantly improve high-intensity interval workout performances. And better performances mean better caloric burns.
Meanwhile, if you don't consume enough carbs to meet both your basic biological needs plus those needed to fuel your exercise, your body will earmark whatever carbs you do have for your brain. As a result, your workout may feel harder and your performance may actually decline.
People who are trying to lose weight and are exercising regularly as part of their strategy make be able to increase their carb intake above the RDA, Layman says. "If you go to the gym regularly and stay pretty active," you can add approximately 60 grams of carbohydrates per hour of exercise and still lose weight, he says.
Consuming healthy snacks before and/or after your workouts can help refuel your body. "You could do a pre-or post-workout snack," DiMarino says. A healthy snack would include an equal proportion of protein and carbs. Such snacks include a cup of yogurt with berries, a glass of low-fat chocolate milk, or a few slices of deli turkey on a whole-grain wrap or tortilla.
"Weight loss is not only determined by how many carbs you eat, but about how many calories you consume," DiMarino says. "It's important to understand how much carbohydrates, protein, and fats you eat each day and how many calories in total you get from those macronutrients."
DiMarino recommends seeking out a registered dietitian who can help you determine how much of these macronutrients you need while trying to reach your goals, whether it's weight loss or something else.