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Carbohydrates Explained: Why Your Body Needs Them

By: Cami Eastman, RDN, LD on 10/18/2026

Digestive Health Nutrition 101
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Depending on who you follow online, you may have heard that carbs like bread, fruit, rice or potatoes spike your blood sugar, cause weight gain, increase inflammation, or should be limited if you want to be “healthy.”

Carbohydrates have become one of the most misunderstood nutrients. But carbohydrates are an important source of energy for the body, and many carbohydrate-rich foods provide fiber, vitamins, minerals, and other nutrients that support long-term health.

The research also doesn't support treating all carbohydrates as if they affect the body in the same way. A bowl of lentils and a glass of soda both contain carbohydrates. Nutritionally, they are very different foods.

So rather than asking: “Are carbs good or bad?”

A more useful question is: “What kinds of carbohydrate foods am I eating, and what else are they providing?”

What Are Carbohydrates?

Carbohydrates are one of the three primary macronutrients, along with protein and fat.

They're found naturally in many foods, including:

  • grains
  • beans and lentils
  • fruit
  • starchy vegetables
  • milk and yogurt
  • nuts and seeds
  • vegetables

They're also found in foods containing added sugars, such as soda, candy, baked goods, and sweetened beverages.

When you eat carbohydrates, your digestive system breaks many of them down into glucose, which can enter your bloodstream and be used by your cells for energy.

But energy isn't the only thing carbohydrate-containing foods provide. Depending on the food, they can also provide fiber, B vitamins, iron, calcium, potassium, antioxidants, and many other nutrients.

That's one reason nutrition recommendations based solely on the number of carbohydrate grams can miss the bigger picture.

Why Does Your Body Need Carbohydrates?

One of carbohydrates' primary jobs is providing energy. Your brain relies heavily on glucose, and red blood cells depend on glucose for energy. Your muscles also use carbohydrate—stored as glycogen—to support physical activity, particularly as exercise intensity increases.

This doesn't mean the body becomes incapable of functioning when carbohydrate intake is low. Humans have metabolic pathways that allow us to adapt to different macronutrient intakes. But being able to adapt to a very-low-carbohydrate diet isn't the same thing as carbohydrates being unnecessary or harmful.

For most people, carbohydrates are an efficient and practical way to fuel everyday life.

Do Carbohydrates Turn Into Sugar?

This is one of those nutrition statements that's technically based on physiology but often presented without enough context. Many carbohydrates are broken down into glucose. That's supposed to happen.

Glucose isn't a toxin your body is desperately trying to eliminate. It's an important source of energy. After you eat carbohydrate, blood glucose rises. Your pancreas releases insulin, which helps move glucose from your bloodstream into cells where it can be used or stored. That process is normal physiology.

The fact that a food raises blood glucose doesn't automatically make it unhealthy. The amount and type of carbohydrate, what else is eaten with it, your activity level, medications, health conditions, and individual physiology can all influence the glucose response.

This becomes particularly important for people with diabetes or other conditions affecting glucose regulation, but the solution still isn't necessarily to eliminate carbohydrates altogether.

Are Carbohydrates Bad for Blood Sugar?

Again, it depends on the carbohydrate. Imagine comparing: Soda with black beans. Both provide carbohydrate, but beans also provide protein, fiber, vitamins, minerals, and plant compounds. Their fiber and physical structure also affect how they're digested.

The same distinction applies when comparing fruit juice with whole fruit or a refined grain with an intact whole grain. This is why carbohydrate quality often tells us more than carbohydrate quantity alone.

Foods such as:

  • beans
  • lentils
  • chickpeas
  • oats
  • barley
  • brown rice
  • quinoa
  • whole-grain breads
  • potatoes
  • corn
  • fruit
  • vegetables

can all contribute carbohydrates within a nutritious eating pattern.

For people who need to manage blood glucose, the amount and distribution of carbohydrate may also matter. But that is different from saying carbohydrates themselves are unhealthy.

Do Carbs Make You Gain Weight?

No single macronutrient has a unique ability to automatically cause weight gain simply because you eat it. This includes carbohydrates. Low-carbohydrate diets are often marketed around the idea that carbohydrates raise insulin and therefore uniquely promote fat storage.

If that were the primary driver of long-term weight change, we'd expect low-carbohydrate diets to consistently outperform diets containing more carbohydrates when compared in controlled studies. That's not what the research shows.

Research comparing low-carbohydrate diets with more balanced approaches generally finds little to no meaningful difference in long-term weight outcomes.

In other words, the evidence doesn't support the idea that carbohydrates are uniquely responsible for weight gain or that restricting them is necessary for maintaining health.

Not All Carbohydrates Are the Same

Calling a food a “carb” can obscure most of what matters nutritionally. Consider:

  • Lentils provide carbohydrate, fiber, protein, iron, folate, potassium, and other nutrients.

  • Fruit provides carbohydrate along with fiber, vitamins, minerals, water, and phytochemicals.

  • Whole grains provide carbohydrate, fiber, B vitamins, minerals, and other plant compounds.

  • Milk and yogurt contain carbohydrate in the form of lactose while also providing protein, calcium, and other nutrients.

  • Candy primarily provides carbohydrate from added sugars and may provide fewer additional nutrients.

That doesn't mean you need to classify the first group as “good carbs” and candy as a “bad carb.” It means foods have different nutritional roles.

Candy can provide pleasure and quick energy. Beans can provide fiber, protein, and sustained nourishment. Fruit can provide carbohydrate, hydration, fiber, and micronutrients.

Nutrition becomes more useful when we look at the whole food instead of assigning moral value to one nutrient.

What Makes a Carbohydrate More Nutrient-Dense?

One of the clearest differences between carbohydrate-rich foods is fiber.

Fiber is a type of carbohydrate that isn't completely broken down and absorbed in the small intestine.

Different types of fiber can support:

  • bowel regularity
  • digestive health
  • cholesterol management
  • blood glucose regulation
  • the gut microbiome
  • cardiovascular health

Fiber-rich foods also tend to bring other nutrients along with them.

Some of the most useful sources include:

  • beans and lentils
  • whole grains
  • fruits
  • vegetables
  • nuts
  • seeds

Large research reviews have found remarkably consistent associations between higher fiber intake and better long-term health outcomes.

What Does the Research Say About Fiber?

One of the largest analyses informing international carbohydrate recommendations examined 185 prospective studies and 58 clinical trials.

Higher fiber intake was associated with a 15–30% reduction in all-cause and cardiovascular mortality, coronary heart disease, stroke, type 2 diabetes, and colorectal cancer when people with higher intakes were compared with those consuming less fiber.

Clinical trials also found improvements in several cardiometabolic risk factors. Importantly, researchers found a dose-response relationship: benefits generally increased as fiber intake increased.

The analysis identified approximately 25–29 grams of fiber per day as a useful target range, with evidence suggesting additional benefits may occur at higher intakes. That's a much more meaningful nutrition target than simply trying to eat “fewer carbs.”

Whole Grains Are Carbohydrates, Too

Whole grains are another good example of why treating all carbohydrates alike doesn't make sense. Whole grains retain the bran, germ, and endosperm of the grain.

That means they generally contain more:

  • fiber
  • B vitamins
  • minerals
  • phytochemicals

than their more refined counterparts.

Examples include:

  • oats
  • barley
  • brown rice
  • quinoa
  • bulgur
  • farro
  • whole wheat
  • whole rye
  • corn

Research consistently associates greater whole-grain intake with better cardiometabolic outcomes. You don't need every grain you eat to be whole grain. But regularly incorporating whole grains is one practical way to increase fiber and nutrient variety without counting carbohydrate grams.

What About Refined Carbohydrates?

Refining grains removes parts of the original grain, which generally reduces fiber and some naturally occurring nutrients. Examples include many foods made primarily with refined white flour.

That doesn't make white bread, crackers, white rice, or pasta foods you need to fear or eliminate. You might prefer white rice with a particular cultural dish. White bread may be easier to tolerate during a GI flare.  Regular pasta may be what your family likes and can afford. A cracker may be exactly what sounds manageable when you're nauseated.

Nutrition doesn't require making the “most nutritious” choice every time you eat.  Instead, think about your overall pattern. If most of your carbohydrate intake comes from foods with very little fiber or nutritional variety, adding some whole grains, beans, fruits, or vegetables can increase what your diet provides without requiring you to eliminate foods you enjoy.

What About Added Sugar?

Added sugars are carbohydrates added to foods and beverages during processing or preparation, rather than sugars naturally present in foods like fruit and milk.

While you don't need to eliminate added sugar, reducing excessive intake can support cardiovascular and metabolic health. The American Heart Association recommends limiting added sugars to no more than 6% of daily calories.

A few practical places to start:

  • Look at what you're drinking. Soda, sweetened coffee drinks, energy drinks, and sweet teas can be significant sources of added sugar. Try reducing the amount of sweetener, choosing a smaller size, or alternating with unsweetened options.
  • Consider frequency and portions. If you're regularly consuming several sources of added sugar throughout the day, look for opportunities to reduce some without eliminating foods you enjoy.
  • Keep foods you enjoy in your diet. Desserts, sweetened foods, and beverages can still fit into a balanced eating pattern. The goal is to be mindful of how much added sugar you're consuming overall, not to avoid it entirely.

Focus on reducing added sugars where changes feel practical and sustainable, particularly from beverages, rather than trying to eliminate every food that contains sugar.

Should You Pair Carbohydrates With Protein or Fat?

You've probably heard that you should “never eat a carb by itself.” That's another nutrition rule that doesn't need to be universal.  Adding protein, fat, or fiber to a carbohydrate-containing meal or snack can affect digestion, fullness, and blood glucose response.

For example:

  • Apple → Apple + peanut butter

  • Toast → Toast + eggs

  • Crackers → Crackers + cheese

  • Rice → Rice + tofu + vegetables

Those combinations may be more filling and provide a wider variety of nutrients. But that doesn't mean eating an apple by itself is somehow nutritionally wrong.  Sometimes you want an apple. Sometimes you need quick energy before exercise.  Sometimes crackers are what you can tolerate.

Pairing foods is a tool, not a rule.

Do You Need to Eat 45–65% of Your Calories From Carbohydrates?

Current reference ranges commonly place carbohydrate intake at approximately 45–65% of total energy for the general population. But that doesn't mean you need to calculate what percentage of your calories comes from carbohydrates.

Individual needs and preferences vary. Someone who eats more carbohydrate isn't automatically eating better. Someone who eats less isn't automatically eating worse. And for people with certain medical conditions, including diabetes, an individualized carbohydrate intake may be appropriate.

For most people, a more practical question is: Am I regularly getting carbohydrate-rich foods that also provide fiber and other nutrients?

That shifts the focus away from micromanaging percentages and toward the actual foods on your plate.

What About Low-Carbohydrate Diets?

Low-carbohydrate diets can be one way of eating. Some people enjoy them. Some people find them helpful for managing certain health conditions. Others find them restrictive, unsatisfying, difficult to maintain, or incompatible with their cultural foods and preferences.

Research shows that different eating patterns can support metabolic health, including those with higher or lower carbohydrate intakes. While reducing carbohydrates may help some people with type 2 diabetes manage blood glucose, the benefits vary, and more restriction isn't necessarily better.

The types of foods you eat matter as much as the amount of carbohydrate. Fiber-rich foods such as whole grains, beans, lentils, fruits, and vegetables can support blood glucose regulation, cholesterol levels, and long-term cardiovascular health.

Long-term comparisons generally don't show a dramatic universal advantage to carbohydrate restriction. And there's an important question that gets lost when we focus exclusively on macronutrient percentages:

What replaced the carbohydrates?

Replacing refined carbohydrates with beans, vegetables, nuts, seeds, or other nutrient-rich foods is very different from replacing whole grains, fruit, and legumes with large amounts of saturated fat. Diet quality still matters.

You Don't Need to Earn Carbohydrates Through Exercise

Carbohydrates often get framed as something you need only if you're very active.

You'll sometimes hear: If you're not exercising, you don't need carbs.

That's not how human metabolism works. Your brain, nervous system, organs, and cells require energy whether you're running a marathon, working at a desk, recovering from illness, studying for an exam, or resting on the couch.

Physical activity can certainly change your energy and carbohydrate needs. But food isn't something you have to earn through movement. Resting bodies need fuel, too.

Carbohydrates Can Be Especially Important for Exercise

While you don't need to exercise to “deserve” carbohydrates, carbohydrate availability becomes particularly important during many forms of physical activity. Your muscles store carbohydrate as glycogen.

As exercise intensity increases, carbohydrate becomes an increasingly useful fuel source. Adequate carbohydrate can help support:

  • training
  • endurance
  • recovery
  • glycogen replenishment
  • performance

That's one reason aggressively restricting carbohydrates can be counterproductive for some active people. Your needs depend on the type, duration, and intensity of activity, but carbohydrates aren't the enemy of athletic performance. They're fuel.

Are Fruit and Potatoes “Too High in Carbs”?

Foods sometimes get criticized online simply because they contain a substantial amount of carbohydrate. Fruit and potatoes are common examples. But carbohydrate content alone doesn't tell us whether a food is nutritious.

  • Fruit provides fiber, vitamins, minerals, water, and phytochemicals.

  • Potatoes provide potassium, vitamin C, carbohydrate, and other nutrients.

Neither food needs to be justified by having a low glycemic index or being “balanced” perfectly with another food. They can simply be part of a varied eating pattern.

A More Useful Way to Think About Carbohydrates

Instead of asking: How can I eat fewer carbs?

try asking:

  • Where can I get more fiber?

  • Could I include beans or lentils more often?

  • Do I eat fruits and vegetables regularly?

  • Are there whole grains I actually enjoy?

  • Am I eating enough throughout the day to support my energy needs?

  • Are food rules making eating more stressful than it needs to be?

These questions tell us much more about nutrition than whether you ate 100, 200, or 300 grams of carbohydrate yesterday.

Easy Ways to Add Fiber-Rich Carbohydrates

You don't need to overhaul your diet. You might:

  • Add beans to tacos or quesadillas.

  • Use lentils in soups, curries, or pasta sauce.

  • Choose oatmeal for breakfast.

  • Add fruit to yogurt or cereal.

  • Try brown rice, barley, bulgur, farro, quinoa, corn, or another whole grain you enjoy.

  • Add chickpeas to salads or grain bowls.

  • Snack on fruit, popcorn, or whole-grain crackers.

  • Keep frozen fruits and vegetables available when fresh produce isn't practical.

And these examples aren't a checklist, you don't need to eat all of them. The goal is to build a carbohydrate pattern that provides energy, fiber, nutrition, enjoyment, and enough flexibility to fit your actual life.

The Bottom Line: Your Body Needs Carbohydrates

Carbohydrates aren't one single type of food, and labeling them collectively as “good” or “bad” isn't particularly useful. They provide an efficient source of energy, and many carbohydrate-rich foods—including whole grains, beans, lentils, fruits, and vegetables—are consistently associated with positive health outcomes.

Research also doesn't support the idea that carbohydrates are uniquely responsible for weight gain or that everyone benefits from restricting them. Instead of focusing on eating as few carbohydrates as possible, pay attention to carbohydrate quality, fiber, variety, and your individual needs.

Looking for Support With Nutrition Without Food Rules?

If you're trying to improve your nutrition but feel overwhelmed by conflicting advice about carbohydrates, blood sugar, sugar, weight, or what you're “supposed” to eat, nutrition counseling can help.

At Nutrition Ally, we use an evidence-based, weight-inclusive approach to nutrition. Instead of eliminating entire food groups, we help you understand what your body needs and build realistic eating patterns around your health, preferences, culture, and lifestyle.

Schedule a discovery call to learn more about individualized nutrition counseling.

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