Low-Glycemic Diet vs. Low-Carb Diet: Which Is Healthier?

Millions of Americans go on a diet each year for various reasons, whether it's to better manage a health condition or simply a desire to feel better in one’s own skin. As you begin to consider the endless list of diets on the internet, you might ask yourself: Is this one actually healthy for me?

 Two diets that have held the spotlight for some time and have had countless studies published on them are often confused: the low-glycemic diet and the low-carb diet. While both aim to improve health, each comes with a unique set of differences. In this article, we discuss each diet, sift through the research and explain which is the healthier option for your goals. 

 What Is the Low-Glycemic Diet? 

 Perhaps at your most recent annual checkup, your doctor advised you to start “watching your carb intake” as your latest A1C (hemoglobin A1C, which is a three-month average of your blood sugar levels, per MedlinePlus) crept up to risky heights. Upon doing some research, you discover the low-glycemic diet.

 The low-glycemic diet doesn’t require you to cut carbs (phew!), but does emphasize choosing low-glycemic foods over high-glycemic foods. Foods that contain carbohydrates—anything from an apple to a bowl of pasta salad to a cookie—are all rated with a value from 0 to 100 on the glycemic index. 

 Foods with a low glycemic index (GI) of 55 or less are mostly fruits, vegetables, beans, yogurt and nuts. These are deemed to be low-glycemic foods and are given the green light to regularly add into your eating pattern. On the other hand, foods considered high GI are those with a GI of 70 or higher. These foods include things like baked goods, white rice, white bread and certain cereals. 

According to the Glycemic Index Foundation, foods with a high GI can cause your blood sugar to spike and then quickly fall, which is why they should be enjoyed in a more limited way. A food with a low GI will help keep your blood sugar levels stable and may help you lose weight, improve your energy levels and reduce your risk for certain health conditions, including diabetes.

 However, this approach comes with limitations. For one, the diet doesn’t look at a food as a whole, and some highly nutritious foods have a high glycemic index. For example, watermelon has a GI of 70; however, this juicy fruit is low in total calories, high in antioxidants and water, and most dietitians would agree it’s a good choice for many healthy eating patterns. Secondly, the low-glycemic diet has a strong emphasis on portion sizes, which can be easy to misjudge. Finally, not all foods are listed on the glycemic index, so you might be left stumped when you cannot find a specific GI number for your favorite food.

What Is the Low-Carb Diet? 

 The diet that puts a cap on the amount of carbs you can eat each day is a low-carb diet. The low-carb diet has become so popular that there are many variations of it, such as the Atkins diet, Whole 30 and the South Beach Diet—all of which emphasize low-carb intake but also come with their own set of diet rules. 

In general, the low-carb diet limits your total carbohydrate intake to a percentage of your total daily calories or provides a specific total gram amount to consume each day. The National Library of Medicine defines a low-carbohydrate diet as one that gets less than 26% of your daily calories from carbs, or less than 130 grams of total carbs per day. The goal of this diet is to assist with weight loss and help manage blood sugar levels. 

 The low-carb diet, however, differs from the keto diet. The keto diet is very low carb, allocating less than 10% of total calories to come from carbs, or approximately 20 to 50 grams of carbs per day—which is barely enough to eat a banana! Here at EatingWell, we recommend that you don’t drop below 40% of your calories from carbs, or go below 120 grams of carbs per day. Drastically reducing your carb intake may prevent you from consuming sufficient vitamins, minerals and fiber found in carb-rich foods like fruits, veggies, whole grains and legumes. Additionally, filling up on certain foods frequently recommended on keto diets, such as bacon, butter or full-fat cheese, may actually have adverse effects on heart and digestive health if consumed in excess over time. 

Which Is Healthier? 

Which brings us to the question: Which diet—the low-glycemic diet or low-carb diet—is the healthier option? Let’s take a closer look at the research. 

 The low-glycemic diet has been found to be favorable for cholesterol and blood sugar control, specifically for people living with or at risk for diabetes, compared to other diets. According to a 2019 meta-analysis published in The American Journal of Clinical Nutrition, participants who followed the low-glycemic diet had lowered A1C, fasting blood glucose, total cholesterol and LDL cholesterol compared to other diets. Another 2022 meta-analysis published in the journal Nutrients found the low-glycemic diet was also effective in lowering blood sugar levels and slightly reducing body mass.

 On the flip side, the low-carb diet has been touted for its weight-loss benefits. But when compared to a low-fat diet, there wasn’t too much difference in results among participants, according to a 2022 meta-analysis published in Frontiers. Researchers also saw no difference in health benefits (e.g., blood sugar or cholesterol levels) when placing both a low-fat and low-carb diet side-by-side. Furthermore, following a very low-carb diet may hamper your mood. A 2023 meta-analysis published in the Journal of Affective Disorders found that a low-carb diet significantly increased anxiety when participants’ diets contained less than 26% carbs. The American Heart Association also ranked the low-carb and very low-carb diet, such as the keto diet, at the very bottom of their list for diets that promote heart health.

 The Bottom Line

 According to recent research, the low-glycemic index diet may offer more health benefits than a low-carb diet. Both low-glycemic and low-carb diets have potential for weight loss; however, the low-glycemic diet shows greater advantages in lowering blood sugar and cholesterol levels and isn’t as restrictive. Additionally, a very low-carb diet may affect one’s mood, has not been shown to promote heart health and isn’t a sustainable diet plan to follow for the long term.

 As a registered dietitian nutritionist, I am not one to promote fad diets or any one specific diet. While the low-glycemic diet might be beneficial for some, it may not be a fit for everyone. Diets have limitations and downfalls. Plus, what might work for you may not work for someone else. Nutrition is personal and each person has a unique set of needs, medical history, food preferences and goals that need to be taken into consideration before implementing any type of meal plan. Consulting with a registered dietitian nutritionist before starting any diet or meal plan is always recommended.