Do carbs make you gain weight? Are low-carb diets effective? A registered dietitian sets the record straight on carbohydrates.
Carbohydrates are an important part of a healthy diet. So why do so many people still believe that carbs make you gain weight and that a low-carb diet is the best way to lose weight? Here, Marilyn Holmes, a registered dietitian with Vanderbilt University, weighs in on some of the most common myths associated with carbs.
Simple versus complex carbohydrates
First, it is important to understand the difference between the two broad categories of dietary carbohydrates: simple and complex. Simple carbohydrates are synonymous with simple sugars, which are found in high concentrations in sodas, candy, honey, syrup, sports drinks and energy drinks, doughnuts, pastries, cookies and cakes. Many of these products are referred to as “empty-calorie” foods, which simply means that they have very low nutritional value. You won’t find many vitamins, minerals, phytochemicals (non-nutrients in plant-based foods that help prevent disease) or much fiber in most foods and beverages that are high in simple carbs.
Complex carbohydrates are plant-based foods and include things such as fruits, vegetables, whole grains and legumes. Unlike their simple counterparts, complex carbohydrates are loaded with fiber, vitamins, minerals and phytochemicals. Except for fruit, people are often surprised to learn that most complex carbohydrates are also a significant source of dietary protein, too. So, whenever we talk about dietary carbohydrates, it’s very important to distinguish the simple from the complex.
Myth #1: Carbs make you fat.
“Aim to eat complex, whole grains instead of refined grains. Whole grains are less processed and contain more fiber, which makes you feel more full, which is an important key to maintaining a healthy weight.”
Our body weight is dictated by the number of calories we consume each day versus the number of calories we expend. Consuming too much of anything (even the healthy foods) can result in weight gain if we consume more calories each day than we expend. It’s extremely important to focus on the quality as well as the quantity of carbohydrates that we take in each day. By limiting simple carbohydrates and emphasizing complex carbohydrates in our diet, we significantly decrease our risk for developing type 2 diabetes, as well as cardiovascular disease and some cancers.
“Weight gain is not due to carbs themselves, but from the over-consumption of any type of food,” Holmes explained. “Aim to eat complex, whole grains instead of refined grains. Whole grains are less processed and contain more fiber, which makes you feel more full, which is an important key to maintaining a healthy weight.”
Limit consumption of refined grains, such as chips, crackers, white bread and pastries. Weight loss is best achieved by limiting overall calories, consuming a sustainable diet of whole grains, lean proteins, low-fat or fat-free dairy products, and eating lots of fruits and vegetables.
Myth #2: Fruit is a sugary carbohydrate, which causes weight gain.
It is true that fruit contains carbohydrates in the form of natural sugar, which is much different than added sugars found in a lot of processed foods. Added sugars contribute to weight gain and increase the risk for chronic diseases like diabetes. Holmes explains that, “According to The 2020-25 Dietary Guidelines for Americans, the top source of added sugar in the American diet is sugar-sweetened beverages, desserts and sweet snacks, which are low in nutrients and can contribute to obesity, increasing heart disease risk. They are also most commonly found in food sources such as juice, snacks, and sweets. The recommendation is to limit added sugars to less than 10% of total daily caloric intake. But, don’t give up your berries and bananas! Fruit is important as part of a healthy diet. Fruits contain fiber, which helps with weight control and digestive health, as well as many vitamins, minerals and antioxidants.”
Myth #3: Carbs shouldn’t be eaten at night.
“Carbohydrates are processed by your body the same way, no matter what time of day it is,” said Holmes. “There is no evidence to support that eating carbohydrates at night will promote unwanted weight gain. Again, be sure to choose whole grains whenever possible and always monitor portion sizes.”
Myth #4: Low-carb diets are the best way to lose weight.
There is no evidence to support that following a low-carb diet is the most effective weight-loss strategy. If carbohydrates are very limited, weight loss is likely a result from calorie restriction and loss of water weight, not from the decrease in carbs themselves.
“This diet is also difficult to sustain long-term and weight gain will likely occur once discontinuing the diet,” Holmes said. “Carbohydrates are the primary fuel source for our brain. Severely restricting carbs can have a negative impact on health as the body will switch to a state of ketosis, when the body burns fat as fuel instead of glucose, which can lead to dehydration and a chemical imbalance in the blood.”
A healthy perspective on carbohydrates
Carbohydrates are essential to survival and disease prevention. Choosing complex carbohydrates from whole grains, fruits, vegetables and beans is a great way to meet fiber, vitamin and mineral needs and to maintain a healthy weight. The USDA’s current Dietary Guidelines for Americans recommend that 45-65% of total daily calories should come from carbohydrates, with most of that in the complex form. If you have metabolic syndrome, you should consume the lower end of the recommended range. On the other hand, if you are highly physically active each day, you may need to consume closer to the upper end of the recommended range.
