A healthy diet: are carbs really the enemy?

“I would wear a sauna suit twice a day, run on the treadmill, completely cut out all sugar and all carbs, and just eat the cleanest veggies and protein,” she told Vogue of her crash diet to lose 16 pounds in three weeks. Many criticized Kardashian for promoting unhealthy habits, but she’s not the only person who’s cut carbs in recent years.

Other celebrities, such as Halle Berry and Megan Fox have popularized low-carb diets like the ketogenic diet, influencing many people’s eating habits. As society once looked as “fat” as the enemy, the same seems to be happening with “carbs.” Let’s see what science says about this trend.

Carbohydrates are essential macronutrients that are the body’s primary source of energy. They are transformed into glucose through digestion, which Men’s Health compares to “high-octane unleaded gas.” If no carbs are available, the body breaks down fat stores for energy.

Simply put, simple carbs are sugars. They can be found in refined sugars like white sugars or corn syrups, or naturally occurring in fruit. Lactose, found in milk and cheese, is also a simple carb. Sugars break down quickly and easily and can spike blood glucose, especially if consumed without fiber.

These carbs are made up of fibers and/or starch. They digest more slowly, make people feel full for longer and avoid the energy crash seen with simple carbs. This category includes breads, fruits, veggies, legumes, nuts, beans, and other grains.

Many nutritionists say it's best to think of carbs on a scale of highly processed to unprocessed. For example, apple juice versus apple sauce versus whole apples. Generally, the more unprocessed version is the healthiest. This also goes for whole grains versus refined grains (like white bread), which have been more processed.

While carbs exist in most foods, some people aim for extremely low-carb (ketogenic, or less that 20% carbs) or no-carb diets. That basically means mostly eating animal products (eggs, meat, seafood) and, maybe, some leafy greens. By removing carbs, fat and protein are the only micronutrients left to eat.

Low-carb diets can promote weight loss, especially in the short term. But, according to the Mayo Clinic, most studies have found that after 12 or 24 months, the weight loss benefits level out with a more well-rounded diet that comes with fewer risks. In fact, with a low-carb diet, most initial weight loss is water weight, as it wipes out the glycogen stores in your body.

Severe carb limitation causes the body to break fat down into ketones for energy. Side effects include bad breath, headache, fatigue, and weakness, besides other short-term side effects like constipation, headaches, and muscle cramps, according to the Mayo Clinic. Long-term risks are not as clear, but studies have found benefits to fiber and whole-grain-rich diets.

Photo: still from 'Keeping up with the Kardashians' / E!

A study by Tufts University found that very low-carb diets may impair cognitive function, as the brain relies on glucose from carbohydrates for energy. In the study, people eating low-carb or no-carb diets showed a gradual decrease in memory tasks.

A study in Nutrients (2021) found that poorly planned low-carb diets can lead to nutrient deficiencies, as many nutrient-rich foods like fruits and veggies are excluded.

A massive 2019 observational study in The Lancet found that diets high in fiber were associated with a 15-30% decrease in heart disease, stroke, type 2 diabetes, and colorectal cancers compared to low-fiber diets.

Higher consumption of total whole grains and several commonly eaten whole grain foods, including whole grain breakfast cereal, oatmeal, dark bread, brown rice, added bran, and wheat germ, was significantly associated with a lower risk of type 2 diabetes, according to a major BJM study from 2020.

A 2022 study published in Human Behavior found that a low-carb diet is linked with depression. The authors even calculated that increasing carbohydrate intake by one standard deviation (roughly 335 Calories) resulted in a 58% lower risk of major depressive disorder, though it's not a panacea.

Image: Crissta Ames Walle / Unsplash

Carbohydrates serve as fuel for high-intensity and endurance exercise. According to Stuart Galloway, an exercise metabolism researcher at the University of Stirling, consuming an additional 40g to 60g of carbs per hour of training can improve performance.

A study in the Journal of the International Society of Sports Nutrition suggests that raising insulin levels by consuming carbohydrates post-workout can aid in protein synthesis and muscle building.

Photo: John Arano / Unsplash

The little microbes living in your gut love carbs like whole grains, pulses (beans and lentils), vegetables (especially cruciferous vegetables), fruits, nuts and seeds, according to researcher Justin Sonnenburg. And your microbiome can have its own powerful effects on the body.

A 2023 meta-analysis found that diets that get more than 60% of energy from carbohydrates are linked to cardiovascular issues in an Asian cohort. The Dietary Guidelines for Americans recommend that carbohydrates make up 45% to 65% of total daily calories.

A Pubmed study looking at China found that carbs accounted for around 68% of all calories. However, 87% of the carbs were in the form of white rice and refined wheat products. That study also showed that people who ate the most refined carbs were two to three times more likely to get heart disease than those who ate the least.

Several studies have shown that carbs like sodas, white bread, pasta or rice, or sweets like cookies that break down fast are linked to overeating, belly fat and an increased risk of many diseases like diabetes. Compared to unprocessed carbs, they are usually much lower in good nutrients too.

Nutritionist Dr. Gail Cresci told Men's Health that consuming refined carbs, such as white bread and pastries, can cause increased blood sugar, insulin levels, and inflammatory compounds, potentially leading to metabolic dysfunction.

While nutrition science is constantly evolving, a balanced diet that includes carbohydrates, proteins, and fats has been found to support health and well-being. But not all carbs are equal, so focus on getting healthy whole grains and fibers versus pure sugars that spike blood glucose.