Is it bad to stay away from carbs? The science behind low-carb diets

November 3, 2025 •

5 min read

According to the American Heart Association, excessive intake of refined sugars and simple carbs can increase the risk of heart disease. This raises a critical question for many: Is it bad to stay away from carbs completely, or is a more balanced approach the key to long-term health?

Quick Summary

Drastically cutting carbohydrates can lead to nutrient deficiencies, low energy, and digestive issues. While popular diets promise quick weight loss, a balanced diet with high-quality carbs is often more sustainable and better for overall health, including gut and heart function.

Key Points

Carbs are Essential: Your body and brain need carbohydrates as their primary fuel source for optimal functioning and energy.
Not All Carbs are Equal: Prioritize complex carbs from whole grains, fruits, and vegetables, which provide fiber and nutrients, over refined and sugary simple carbs.
Risks of Full Elimination: Completely cutting carbs can lead to nutrient deficiencies (especially fiber), low energy, headaches, and digestive issues.
Long-Term Health Concerns: A restrictive no-carb diet may increase risks for conditions like kidney stones, osteoporosis, and heart disease over time.
Balance is Key: A balanced diet with moderate, high-quality carbs is more sustainable and beneficial for overall health than a restrictive low-carb or no-carb plan.
Impact on Brain and Mood: The brain relies on glucose from carbs; a lack can result in 'brain fog' and negatively affect mood and concentration.

The Essential Role of Carbohydrates

Carbohydrates, or carbs, are one of the three main macronutrients, alongside proteins and fats. Despite often being demonized in popular diet culture, they are an essential part of a healthy diet for most people. When you eat carbohydrates, your body breaks them down into glucose, which serves as the primary and most efficient fuel source for your brain, muscles, and central nervous system. Your brain alone uses about 20% of your body's energy, and it prefers glucose to function properly.

Beyond just energy, carbohydrates play several other vital roles. Complex carbs, especially those rich in fiber, are crucial for gut health, promoting the growth of beneficial bacteria and aiding in regular bowel movements. They also help regulate blood sugar and insulin levels, providing a steady release of energy rather than the quick spikes and crashes associated with simple sugars.

The Difference Between Good and Bad Carbs

It's important to distinguish between different types of carbohydrates, as not all carbs are created equal. This distinction is often oversimplified into 'good' and 'bad' categories, but the truth is more nuanced, focusing on minimally processed, whole-food sources versus highly refined ones.

Complex Carbohydrates

These are the 'good' carbs, found in whole, minimally processed foods. They contain longer chains of sugar molecules that take longer for the body to break down and digest.

Whole Grains: Oats, brown rice, quinoa, and whole-wheat bread.
Legumes: Beans, lentils, and peas.
Starchy Vegetables: Sweet potatoes, corn, and parsnips.
Fruits: A wide variety of fruits provide natural sugars and fiber.

Complex carbs are packed with fiber, vitamins, and minerals that support overall health.

Simple and Refined Carbohydrates

These carbs have been processed, often stripped of their fiber and nutrients, and are absorbed quickly by the body.

Sugary Drinks: Soda, fruit juices with added sugar.
Sweets and Baked Goods: Cookies, cakes, and candy.
Refined Grains: White bread, white rice, and many breakfast cereals.

These simple carbs provide a short burst of energy followed by a crash, and excessive consumption is linked to weight gain and an increased risk of chronic diseases.

Risks of Staying Away from Carbs Entirely

Completely cutting carbs is difficult and carries significant health risks, especially over the long term. While a very low-carb diet (like keto) can lead to short-term weight loss by triggering ketosis, the long-term impact on your body can be concerning.

Nutrient Deficiencies: Whole grains, fruits, and vegetables are rich in essential vitamins and minerals like B vitamins, vitamin C, folate, magnesium, and iron. Eliminating these food groups can lead to serious nutritional gaps. A lack of fiber, a type of carbohydrate, is also a major concern, leading to constipation and poor gut health.
Low Energy and Brain Fog: Carbs are the primary fuel for the brain. Without them, the body relies on ketones for energy, which can cause side effects like fatigue, dizziness, headaches, and difficulty concentrating during the initial adjustment period, often called the 'keto flu'. Some people report negative cognitive impacts even after adaptation.
Hormonal Imbalances: Restrictive low-carb diets can elevate the stress hormone cortisol and decrease levels of muscle-building hormones, which can affect metabolic rate and hormonal balance, particularly in women.
Potential Heart and Kidney Risks: Some studies suggest that long-term restriction of carbohydrates, especially when replaced with large amounts of animal fat and protein, may increase the risk of heart disease and kidney stones due to higher blood acidity and increased calcium excretion.
Sustainability and Mental Health: Eliminating an entire food group is highly restrictive and often unsustainable. This can lead to a cycle of deprivation and bingeing, harming your relationship with food and potentially leading to disordered eating patterns.

Low-Carb vs. Balanced Diet: A Comparison


Feature	Very Low-Carb (e.g., Keto)	Balanced Diet (Moderate Carbs)
Carb Intake	Extremely low (typically < 50g/day).	Moderate (typically 45-65% of daily calories).
Weight Loss	Often rapid initial loss (water weight) followed by slower progress.	Slower, more sustainable loss over the long term.
Nutrient Completeness	High risk of deficiencies in fiber, vitamins, and minerals; often requires supplementation.	Easily provides all essential nutrients from a variety of whole foods.
Fiber Intake	Very low; potential for constipation and poor gut health.	Adequate; supports digestion and bowel regularity.
Energy Levels	Initial fatigue ('keto flu'), followed by adaptation; can impair high-intensity exercise.	Consistent, sustained energy from complex carbohydrates.
Sustainability	Highly restrictive and difficult to maintain long-term for many individuals.	Flexible, varied, and easier to adhere to over time.
Long-Term Health Risks	Concerns about kidney stones, bone health, and potential cardiovascular issues, especially with high animal fat intake.	Reduced risk of chronic diseases, including heart disease and type 2 diabetes, when focusing on whole foods.

Finding the Right Balance: A Sustainable Approach

Instead of asking 'Is it bad to stay away from carbs?', a better question might be 'How can I choose the right carbs?' A sustainable and healthy approach focuses on quality and moderation, not elimination. Here’s how you can find the right balance:

Prioritize Complex Carbs: Make whole grains, legumes, fruits, and vegetables the foundation of your carb intake. These provide sustained energy and a wealth of nutrients.
Limit Refined and Added Sugars: Reduce your intake of sugary drinks, candy, and highly processed baked goods. These offer little nutritional value and can lead to health issues.
Use the Plate Method: A simple way to portion meals is to fill half your plate with vegetables and fruits, one-quarter with whole grains, and one-quarter with protein.
Focus on Fiber: Aim for adequate fiber intake, which is found in abundance in whole plant foods. Fiber is essential for digestive health and helps you feel full.
Read Labels: Be mindful of packaged foods and check for added sugars and refined ingredients. Choose minimally processed options whenever possible.
Listen to Your Body: Pay attention to how different foods affect your energy levels and overall well-being. Everyone's needs are different, especially considering age, activity level, and health conditions.

Conclusion: The Final Verdict on Carbs

Ultimately, the answer to the question "Is it bad to stay away from carbs?" is a resounding yes for the vast majority of people. Carbohydrates are not the enemy; the type of carb you consume is what truly matters. Completely eliminating them is often unsustainable and can lead to nutrient deficiencies, hormonal issues, low energy, and digestive problems. While short-term, medically supervised low-carb diets might be beneficial for some conditions like epilepsy, a balanced approach that emphasizes nutrient-dense, complex carbs is the most effective and safe strategy for long-term health. By choosing whole grains, fruits, and vegetables, you can fuel your body effectively while reducing the risk of chronic disease and supporting overall well-being.

For more detailed information on balanced eating, consider resources like the Mayo Clinic's guide to carbohydrates, which provides an excellent overview on incorporating them into a healthy diet.

Frequently Asked Questions

Ketosis is a metabolic state where the body burns fat for energy instead of glucose due to a very low carbohydrate intake. While it's safe for some in the short term, especially with medical supervision for conditions like epilepsy, its long-term effects are not fully understood and may include risks like kidney stones and nutrient deficiencies.

In the short term, a sudden and large drop in carbs can cause flu-like symptoms known as the 'keto flu,' including headaches, fatigue, irritability, and constipation. The initial weight loss is often primarily water weight.

You should limit or avoid highly processed, simple carbohydrates, such as sugar-sweetened beverages, refined grains (like white bread and pastries), candy, and processed snacks. These offer minimal nutritional value and can cause blood sugar spikes.

Yes, they can. By restricting food groups like fruits, vegetables, and whole grains, a low-carb diet may lead to deficiencies in essential nutrients like fiber, B vitamins, vitamin C, magnesium, and iron.

Not all carbs cause weight gain. Weight gain is caused by a calorie surplus, regardless of the macronutrient source. High intake of refined carbs and sugars can lead to overconsumption of calories, but healthy complex carbs are often high in fiber, which can aid in weight management by promoting feelings of fullness.

The best approach is to focus on quality and moderation. Prioritize complex, high-fiber carbs from whole foods like vegetables, fruits, and whole grains. Limit refined sugars and processed carbs. Aim for a balanced diet that includes all macronutrients in appropriate proportions.

Carbohydrates are the body's preferred fuel for muscle activity, especially for moderate- to high-intensity exercise. While the body can adapt to use fat for fuel during low-intensity activity, adequate carb intake is important for replenishing glycogen stores and optimal athletic performance.