Carbs tend to get a bad rap for making people gain weight. However, this is one of the biggest misconception. Most of the time, gaining weight is the direct result of eating too many calories, not just carbs.
In fact, carbs are one of the most important macronutrients you need, and a source of vital energy for your body. They fuel your muscles, and play an important role in brain function related to mood, memory, and more.
Keep reading to understand why carbs tend to get the most blame for weight gain, and whether there is any science behind those claims.
Carbohydrates are one of the three macronutrients— types of calories found in food. Protein and fat are the other two. The main role of carbohydrates are to provide energy to your brain, other organs, and tissues.
When you eat carbohydrates, they are broken down by your gut into glucose and released into your bloodstream. Your pancreas responds by releasing insulin to shuttle that glucose into cells. Many carbohydrate-rich foods also supply vitamins, minerals, and fiber that are important for overall health.
Carbohydrate foods may contain one or more of three distinct types: sugars, starches, and fiber. Starches and fiber are considered complex carbs, while sugars are simple carbs.
Complex carbohydrates are made up of glucose molecules strung together in long chains. Your body must digest or break down complex carbohydrates into glucose molecules in order to absorb them from the digestive tract into the bloodstream, where they can be used for fuel.
Fiber is a type of complex carbohydrate your body cannot digest. Fiber prevents constipation, and helps support feelings of fullness, blood sugar regulation, and cholesterol control. The majority of carbohydrates in your diet should come from complex carbohydrates.
Sugars are also called simple carbs because they are the most basic form of carbohydrates. They can occur naturally in foods, like fruits, vegetables, and milk. Sugars can also be added to foods for sweetness, like a packet of sugar you stir into your coffee or sweetened drinks, candies, and desserts. Sugars added to foods and drinks for sweetness are referred to as added sugars.
The American Heart Association recommends limiting added sugars due to the relationship between an excess added sugar intake and health risks. They advise women to consume no more than 25 grams (g) of added sugar daily or six teaspoons worth. Men should cap added sugar to no more than 36 g per day or nine teaspoons worth. The average American consumes about 17 teaspoons worth of added sugar each day.
Too much added sugar can increase the risk of these and other health issues:
Simple and Refined Carbohydrates
Refined carbs include added sugars as well as complex carbs that have been processed, like white flour and white rice. The processing of grains removes the bran and germ, which gives starches a finer texture and longer shelf life but also strips them of fiber and key nutrients. Sugars can also be refined. One example is the production of high fructose corn syrup from corn.
Simple carbs are shorter chains of glucose, which are broken down faster, while complex carbs are longer chains of glucose that take longer to break down, therefore don’t spike your blood sugar as noticeably.
Carbs don’t inherently lead to weight gain. It most cases, it’s the quality of carbohydrates you eat and how many total calories that is biggest determinant of weight gain.
A 2022 systematic review of previously published studies failed to show that diets weight-reducing diets low in carbs were superior to weight-reducing diets with balanced carbohydrate intake. Data indicated that there was little or no difference in weight reduction and heart disease risk factors over the short (three to 8.5 months) or long term (one to two years).
Another study published in 2020 looked at the effects of a low-fat versus a low-carb diet for weight loss in adults with overweight or obesity. Researchers concluded that for weight loss, neither diet was superior, as long as there was no difference in calorie or protein intakes.
The Type of Carbohydrate Matters
Other research shows that the type of carbohydrates consumed is key. Several studies indicate that a high intake of refined carbohydrates and added sugars ups obesity risk while unprocessed carbohydrate-rich foods are tied to weight loss.
A research review published in 2020 concluded that long-term clinical studies have not shown that all sources of carbohydrate behave equally when it comes to weight loss. High-quality high carbohydrate diets that emphasize fiber-rich whole grains, pulses (beans, lentils, peas, and chickpeas), and fruit are associated with weight loss and a decreased risk of type 2 diabetes and heart disease. Fiber intake in particular is inversely associated with weight gain, meaning the higher the fiber intake the lower the likelihood of weight gain.
In contrast, a high intake of ultra-processed foods, which contain a lot of refined carbs and added sugars and little fiber is linked to weight gain. A 2019 study in 20 weight stable adults looked at how ultra-processed foods affected appetite regulation and food intake compared to unprocessed foods. After being admitted to a clinic, volunteers were randomly assigned to receive either ultra-processed or unprocessed carb-rich diets for two weeks immediately followed by the alternate diet for another two weeks. The subjects were instructed to consume as much or as little as desired. When fed ultra-processed foods the adults consumed about 500 additional calories per day and gained weight. Conversely, they lost weight while eating unprocessed high carb foods.
A 2020 study in a small group of healthy women concluded that a diet rich in high fructose corn syrup reduced the amount of beneficial gut bacteria associated with anti-obesity effects whereas a diet rich in whole fruits increased that same obesity-fighting bacteria.
That said, any calories consumed in excess of what your body needs can contribute to weight gain and ultra-processed foods may make it easier to take in more total calories. A 2022 study found that the consumption of ultra-processed foods increased among U.S. adults across nearly all demographic groups, regardless of income, between 2001 and 2018.
Carbohydrate recommendations differ slightly by health organizations but typically range from 40-65% of total calorie intake with the caveat that added sugar should be limited and fiber-rich, unprocessed carbohydrates should be prioritized.
For a person who needs 2,000 calories per day, 40% of calories from carbohydrate is 800 calories worth or 200 g. For a 1,600 calorie per day, 40% of carb intake is 160 g of carbohydrate per day.
The Recommended Daily Allowance (RDA) for carbohydrates is 130 g per day, which is based on the brain’s daily energy needs.
Total daily calorie needs are determined by age, height, weight, sex, and physical activity level. In general people who are younger, taller, weigh more, and are more active have higher calorie needs.
Healthy ways to incorporate carbohydrates include:
- Make oatmeal a breakfast staple.
- Incorporate fruit into snacks, paired with other nutritious options, like nuts.
- Choose whole grains over refined grains, like brown rice or quinoa in place of white rice.
- Eat more pulses in the form of lentil, black bean, or split pea soup, hummus, or roasted chickpeas.
- Make starchy veggies the carb source in a meal, like roasted fingerling potatoes, sweet potatoes, butternut squash, or roasted corn.
Carbohydrates are one of the three types of calories found in food, but not all carbs are created equal. For weight regulation and overall health, the best approach is to minimize the intake of added sugars, refined carbs, and ultra-processed foods. Instead, choose unprocessed high fiber, nutrient rich carb sources, like fruits and vegetables, whole grains, beans, and lentils.