Low-Carb vs. High-Carb Diets: A New Study Reveals Hidden Risks

Does one carb-modified diet work better than the other?

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If you skim a list of fad diets from the past few decades, you might notice a trend: Carbs are the enemy. The South Beach Diet, the Atkins Diet, and the keto diet all encourage severe carb restriction to help you (allegedly) lose weight.

With these trendy low-carb diets, it’s tempting to assume all carbs are unhealthy. After all, sugar and soft pretzels are carbs, right? Most experts have spoken against this carb-cutting approach, but a new study may now be able to provide more evidence to put out the low-carb fire.

How the Study Worked

The 2018 study published in The Lancet analyzed the diets of 15,428 adults between the ages of 45 and 64 in the late 1980s. The researchers recorded the ratio of carbohydrates in each participant’s diet, categorizing them as low-carb, moderate-carb, or high-carb. Low-carb eating was defined as getting less than 40 percent of your calories from carbs; high-carb diets were defined as greater than 70 percent carbs.

After 25 years, the researchers followed up with the participants and recorded the mortalities. The deaths were compared with the carb intake from the initial survey.

What the researchers found was pretty stunning: The graph showed a U-shaped correlation between carb intake and risk of death. In other words, those who ate at the two extremes (low-carb or high-carb) had higher risk of death compared to those who ate moderate-carb diets. (Keep in mind that correlation does not equal causation.)

This aligns with the Dietary Guidelines for Americans, which recommends that carbs be 45 to 65 percent of your calorie intake. This is referred to as AMDR, or Acceptable Macronutrient Distribution Ranges. Because carbs are the body’s preferred source of energy, they should take up the bulk of calorie intake. The remainder goes to protein (10 to 35 percent) and dietary fat (20 to 35 percent).

Not Just a Numbers Game

But that’s not all the study found. Despite the risk posed by carb-modified diets, the researchers found that the quality of protein and fat in the diet also played a big role in the health of participants.

When eating a low-carb diet, those who focused on animal fats and proteins (e.g. red meat, chicken, cheese, bacon) had an even higher risk of mortality. On the other hand, low-carb eaters who focused on plant-based fats and proteins (e.g. nuts, avocado, soy, whole grains) had a decreased risk of mortality. (Find out how a plant-based diet can also help lower the risk of cancer.)

Moral of the story? When it comes to macronutrients, both quantity *and* quality matter.

What About Diabetes?

First of all, diabetes is a disorder of the metabolism that makes it difficult for the body to use digested carbohydrates for energy. The low-carb diet prescribed by the American Diabetes Association (ADA) is a treatment plan for diabetes and is not meant to be a universal recommendation.

Carb intake for people with diabetes is personal and should be determined by each person’s healthcare team. Still, the ADA addressed the study in its magazine Diabetes Forecast, saying “If you choose to follow a low-carbohydrate diet, replacing the carbs with plant-based proteins may mean a longer life.”

Whether or not someone has diabetes, choosing complex carbohydrates is better than cutting carbs entirely. Complex carbs pack in fiber, which can help improve digestion, cholesterol levels, and even blood sugar control (so complex carbs may help prevent or manage type 2 diabetes).

Instead of chasing rapid and temporary weight loss (which often results in yo-yo dieting), experts recommend making healthy lifestyle changes for the long haul. That includes eating a balanced diet with lots of fruits and vegetables, healthy fats, whole grains (i.e. carbs!), and mostly plant-based protein. Learn more about following a plant-based diet here.