Low-carb diets are often placed on a pedestal, especially when it comes to goals like weight management. This is made no easier by the popularity of Atkins and keto diets, which cut out significant amounts of carbs. But as with all areas of nutrition, low-carb diets (and the carbohydrates themselves) are more nuanced than many realize. In turn, low-carb diets aren’t always necessarily “healthy,” and they certainly aren’t meant for everyone.
We asked registered dietitians to share the potential benefits and risks of low-carb eating, along with who should (and shouldn’t) explore the diet.
Meet Our Expert
- Linda Vero, DCN, MA, RDN, CDCES, doctor of clinical nutrition, registered dietitian nutritionist, and certified diabetes care and education specialist at Hackensack University Medical Center
- Lauren Manaker, MS, RDN, LD, CLEC, registered dietitian at Nutrition Now Counseling
- Kacie Vavrek, RD, registered dietitian at The Ohio State University Wexner Medical Center
Carbohydrates 101
First, know that not all carbohydrates are equal. They fall into two main categories, simple and complex, according to Linda Vero, DCN, MA, RDN, CDCES, doctor of clinical nutrition.
- Simple: Simple carbohydrates are found in refined grains, such as white bread, pastries, and sugary drinks, and they’re digested by the body very quickly, says Vero. “This causes a rapid spike in blood sugar after consumption, followed by a ‘crash’ or rapid decline in blood sugar, which can leave you feeling tired and hungry again soon,” she says.
- Complex: Complex carbohydrates are found in foods such as whole grains, beans, lentils, and vegetables, notes Vero. “They contain longer chains of sugar molecules and are typically rich in fiber and nutrients,” she says. Therefore, your body digests them slowly, providing a steady, more sustained supply of energy with less dramatic blood sugar spikes, Vero says.
This difference matters when reducing (or cutting out) carbs from the diet.
What Is a Low-Carb Diet?
“The term ‘low-carb’ is widely used, but its definition can be surprisingly flexible,” says Vero. In fact, there’s no single, universally agreed-upon number of grams that defines a low-carb diet. “Instead, it’s best understood as a spectrum of carbohydrate restriction compared to a standard diet,” Vero says.
“A typical diet consists of 45 to 65 percent of total daily calories from carbohydrates,” says Vero. “As an example, for someone eating a 2,000-calorie diet, this equals 225 to 325 grams of total carbohydrates per day. Any diet that consistently falls below this range can be considered a form of low-carb eating.”
However, since there are different types of carbohydrates, the specific makeup of low-carb diets can vary widely. “When someone says they’re going low-carb, the effects really depend on which carbs they’re cutting,” says Lauren Manaker, MS, RDN, LD, CLEC, registered dietitian at Nutrition Now Counseling. For example, most dietitians would happily support a change like trimming back on sugary drinks and highly processed snacks, says Manaker. “But if a low-carb plan also strips out complex carbs, you can lose out on fiber and nutrients, which may lead to digestive issues, less fuel for your workouts, and a diet that’s harder to keep balanced over time,” notes Manaker.
The Benefits of Low-Carb Eating
When done mindfully (and with a dietitian’s guidance), low-carb eating can benefit some people.
For example, reducing carbohydrates may help improve blood sugar control and lower triglycerides, and some people experience greater weight loss in the short term, says Kacie Vavrek, RD, registered dietitian at The Ohio State University Wexner Medical Center. And in general, low-carb diets are usually higher in protein and fat, which can keep you full for longer, says Vero. (But as with carbs, there are different sources—so it’s important to pick lean proteins and unsaturated fats, according to Vero.)
Tips
Healthy eating vs low-carb diets: When you reduce your intake of refined grains and added sugars, you may see health benefits. However, it’s worth noting that this change is part of healthy eating in general, not something unique to low-carb diets.
Downsides of Low-Carb Eating
Despite the possible perks of low-carb eating, the diet has some risks:
- Low energy levels. Carbs are your body’s preferred fuel source, so when you drop them quickly, your body needs time to adjust. Initially, some people experience tiredness, brain fog, irritability, and headaches, which is sometimes called the “low-carb flu,” says Manaker.
- Digestive issues. Low-carb eating can also lead to constipation, as it may cut out high-fiber foods. Examples include beans, whole grains, and fruit, says Manaker.
- Nutrition deficiencies. “If not carefully planned, a long-term low-carb diet could lead to deficiencies in fiber and certain nutrients such as potassium, magnesium, folate, and vitamin C,” says Vero.
- High saturated fat intake. If a low-carb diet is high in animal fats and protein, it can increase LDL (“bad”) cholesterol and the risk of kidney stones and other issues, says Vero.
- Weight cycling. “In addition, the restrictive nature of a low-carb diet can make it difficult to follow and maintain long-term, leading to a cycle of weight loss and weight regain,” Vero says.
Now, this doesn’t automatically mean low-carb eating is “unhealthy” or “bad.” It simply means there are many ways to approach the habit, and it should be done mindfully to minimize the risks.
Who Should (and Shouldn’t) Follow a Low-Carb Diet
“Low-carb eating may be helpful for some people with prediabetes or type 2 diabetes, since it can improve blood sugar control, and it can also be an option for people trying to lose weight,” notes Vavrek. Additionally, “a specific, closely monitored version called the ketogenic diet has an established medical role in managing certain types of epilepsy, particularly in children whose seizures don’t respond well to medication,” says Manaker.
In contrast, low-carb eating tends to be less appropriate (or needs extra caution) for people who are pregnant or breastfeeding, endurance athletes who rely on carbs for performance, anyone with certain kidney conditions, and people with a history of disordered eating, since restriction can be a real trigger, says Manaker. “This is exactly why individualized guidance matters so much. What’s helpful for one person may not fit another at all,” she notes.
If you have heart disease or high cholesterol, talk to your healthcare provider before starting a low-carb diet, particularly one that is high in saturated fat. Very-low-carb and ketogenic diets may be high in saturated fat, which can raise LDL (“bad”) cholesterol. The American Heart Association recommends emphasizing unsaturated fats in place of saturated fats as part of a heart-healthy eating pattern.
Why Low-Carb Diets Aren’t for Everyone
Low-carb diets aren’t one-size-fits-all. Nutrition needs, health conditions, food preferences, and lifestyles vary from person to person, says Vavrek. Also, there are many ways to eat a low-carb diet. “A low-carb diet that includes vegetables, nuts, seeds, healthy fats, and quality protein is very different from one high in processed meats and saturated fat [and low in] fiber-rich foods like fruit, beans, and whole grains,” Vavrek says.
So, before starting a low-carb diet (or making any dietary change, for that matter), be sure to chat with a healthcare provider, like a registered dietitian. They can determine if it’s right for you, and if so, how to do it properly. “A low-carb diet is a powerful eating pattern, but it’s also a major medical and lifestyle intervention,” says Vero. This means it needs careful planning to ensure nutritional adequacy, along with awareness of the potential side effects and risks, she notes.
Otherwise, instead of focusing on simply eating fewer carbs, think about carbohydrate quality and overall eating pattern, says Vavrek. “Good nutrition is rarely about eliminating one food or nutrient. It’s about finding a balanced, nutrient-rich way of eating that supports your individual health needs and is sustainable long term,” Vavrek says. Likewise, Manaker notes that health isn’t measured by how few carbs you eat. Instead, “it shows up in the overall quality and balance of your meals, how sustainable your habits feel, and how you actually feel living your life,” Manaker says.
