Carbohydrates: Are they good or bad for you?

What to expect in this article

This overview shows how differently “carbohydrates” can look. The fiber figures are rounded guideline values per 100 grams of food ready to eat and vary depending on the variety and preparation – the information on the package is decisive:

What happens to carbohydrates in the body can be summarized in four steps:

The Short Answer: Good or Bad?

Carbohydrates are neither categorically good nor categorically bad. Four factors are decisive: type, amount, degree of processing, and context.

The type indicates whether it is rapidly available sugar, more slowly digested starch, or indigestible fiber—three groups that behave very differently in the body. The degree of processing also determines how quickly the energy reaches the bloodstream: A whole grain must first be broken down, while fine white flour has already been preprocessed. Context means everything else: physical activity, the amount of protein, fat, and vegetables on the same plate, and total energy intake.

In everyday life, this means it is about patterns, not individual foods. Anyone who mainly eats whole grains, legumes, vegetables, and fruit, while keeping sweetened drinks as an exception, has covered the essentials—even if cake is added on Sundays. Sorting foods into “allowed” and “forbidden” tends to lead to frustration rather than a sustainable way of eating; looking at the overall pattern leaves room for enjoyment.

What Are Carbohydrates—and What Happens to Them in the Body?

Carbohydrates are a group of substances that primarily provide energy. They are classified according to how many sugar building blocks they contain.

From Monosaccharides to Fiber

Monosaccharides are simple sugars: glucose, fructose, and galactose. Glucose is the primary energy carrier and is measured as “blood sugar”; fructose is metabolized mainly in the liver and has less immediate effect on blood sugar.

Disaccharides consist of two building blocks: sucrose, lactose, and maltose. If the enzyme lactase is missing, lactose is fermented undigested in the large intestine—the mechanism behind lactose intolerance. Polysaccharides are long glucose chains: starch is the plant storage form, while glycogen is the human storage form.

Fiber is also a carbohydrate—just the kind that human enzymes cannot break down: cellulose, pectins, beta-glucans, and inulin. It provides little usable energy and acts more as a regulator than as fuel—which is why the catch-all category “carbohydrates” on food labels is not very helpful.

Digestion, Insulin, and Glycogen Stores

Starch digestion begins in the mouth with salivary amylase; the small intestine does most of the work, where enzymes break the chains down into simple sugars—only these enter the bloodstream. Fiber is partially fermented into short-chain fatty acids in the large intestine.

Insulin is the key, not the villain: it signals cells to take up glucose—without insulin, they cannot use it, which is the fundamental problem in type 1 diabetes. The problem arises only when insulin secretion remains chronically high as insulin action declines (insulin resistance), a process that develops over years.

The body stores glucose that is not immediately needed as glycogen in the liver and muscles. Glycogen binds water—which is why, at the beginning of a severely carbohydrate-restricted diet, people often lose one to several kilograms within a few days: predominantly water, not body fat.

After a meal, blood sugar peaks after 30 to 60 minutes and returns to normal within two to three hours in metabolically healthy people. A single sharp rise is not a problem—it becomes relevant when blood sugar remains elevated for a long time on a regular basis.

How meaningful are the glycemic index and glycemic load?

The glycemic index and glycemic load are useful conceptual tools, but in everyday life they have limited significance: they describe laboratory conditions that have little to do with a normal meal.

What GI and GL measure

The glycemic index (GI) indicates how much blood sugar rises after consuming 50 grams of digestible carbohydrates from a food—compared with pure glucose (value 100). The catch: 50 grams are always measured, regardless of how much one would have to eat to obtain that amount; with watermelon, this produces a portion that no one eats all at once. The glycemic load (GL) corrects for this by taking the amount consumed into account—but it, too, remains an approximation.

Three reasons why GI tables are unreliable in everyday life

First, the composition of the meal changes the outcome: fat, protein, acid, and fiber slow gastric emptying. Second, cooking time, degree of grinding, cooling, and ripeness shift the blood sugar response. Third, individual responses vary—two people can eat the same bread and show different patterns.

Which carbohydrate sources are beneficial, and which are less so?

Alongside energy, beneficial sources provide fiber, vitamins, minerals, and phytonutrients. Less beneficial sources mainly provide energy.

According to the WHO guideline on carbohydrate intake (2023), carbohydrates should primarily come from whole grains, vegetables, fruit, and legumes; adults are recommended to consume at least 400 g of vegetables and fruit and at least 25 g of naturally occurring dietary fiber per day.

Whole grains, legumes, vegetables, and fruit

Whole-grain products contain the bran and germ and therefore significantly more fiber, B vitamins, and minerals than refined flour; they keep you full for longer. Legumes provide carbohydrates and plant-based protein at the same time. Fruit contains fructose packaged with water, fiber, and micronutrients—the sugar in a whole apple does not count as free sugar, whereas fruit juice, syrup, and honey do.

White flour, sweets, and sugary drinks

White-flour products are not harmful, but they are low in fiber. Sugary drinks are the clearest problem: liquid sugar is barely filling and is hardly compensated for during later meals. Sweets and pastries are treats—not a reason to feel guilty, but unsuitable as a main source of energy. The difference lies in frequency, not in the individual piece.

Five changes that make the biggest difference in everyday life

How many carbohydrates are beneficial?

There is no one right amount for everyone. However, the professional societies operate within a similar range—with the emphasis on quality rather than the number of grams.

According to the German Nutrition Society (DGE), a balanced mixed diet should provide more than 50 percent of energy intake in the form of carbohydrates.

In its 2010 opinion, the European Food Safety Authority (EFSA) considers a carbohydrate intake of 45 to 60 percent of energy intake appropriate—for adults and for children over one year of age.

Free sugars: the clearest figure in the whole field

Free sugars include all added sugars as well as the sugars in honey, syrup, and fruit juice; the sugar in whole fruit, vegetables, and milk does not count.

Since 2015, the World Health Organization (WHO) has recommended reducing free sugar intake in adults and children to below 10 percent of total energy intake—and sees additional health benefits in reducing it further to below 5 percent.

At 2,000 kilocalories, 10 percent is about 50 grams, and 5 percent about 25 grams. Half a liter of soft drink largely uses up the 10-percent limit.

Fiber: the amount most people fall short of

The DGE guideline for fiber recommends at least 30 grams per day for adults.

Without whole grains, legumes, vegetables, and fruit, reaching 30 grams is difficult—so the fiber recommendation is essentially a recommendation to consume certain sources. Increase your intake gradually and drink enough fluids. These guidelines are also population-level recommendations: Endurance athletes need more than someone with a sedentary job, and deviations for people with type 2 diabetes should be managed with professional guidance.

Low carb, keto, and more: What does the research say?

Low-carbohydrate diets often lead to faster weight loss in the short term, but in the long term they differ little from balanced calorie-reduction diets.

How low-carb and keto differ

“Low carb” is not a protected term and ranges from moderate to very strict. With a ketogenic diet, carbohydrate intake falls so low that the liver produces more ketone bodies. It has an established medical application, for example in treatment-resistant epilepsy, but as an everyday diet it is demanding and has been little studied over the long term.

The Cochrane Review by Naude and colleagues (2022)

A Cochrane Review by Naude et al. (2022), which included 61 randomized controlled trials and 6,925 participants, found that after 12 to 24 months, low-carbohydrate and balanced calorie-reduction diets differed in average weight loss by about 0.9 kilograms—a difference of little clinical significance.

Notably, the review does not show a clear advantage in cardiovascular risk factors beyond the effect of weight loss.

If you have type 2 diabetes, adjustments should be made under medical supervision, especially when taking blood sugar-lowering medication or insulin. Strict restrictions without professional guidance are also not advisable during pregnancy and breastfeeding or if you have a history of eating disorders.

Carbohydrates in the evening and other myths

Four claims come up particularly often—none of them stands up to closer scrutiny.

Myth 1: “Carbohydrates in the evening make you fat”

The body does not keep a clock. Whether you gain weight depends on your energy balance over days and weeks, not the time of day: studies with a constant calorie intake and different distributions found no relevant differences in body fat. Anyone who spontaneously eats large quantities in the evening is more likely to exceed their needs—it is a quantity problem, not a carbohydrate problem.

Myth 2: “Insulin makes you fat”

The carbohydrate-insulin hypothesis claims that carbohydrates directly force fat storage through insulin secretion. Controlled studies with equal calorie and protein intake have not confirmed this. Insulin regulates when energy is stored and when it is mobilized—how much overall is determined by energy balance.

Myth 3: “Sugar is poison” and “Fruit has too much sugar”

Sugar is a nutrient, not a toxin. The WHO limits free sugars because high amounts are associated with tooth decay and higher energy density—not because sugar molecules are poisonous. Fruit is explicitly considered one of the preferred sources: its sugar is contained in a matrix of fiber, water, and micronutrients.

Myth 4: “The body does not need carbohydrates”

Formally, there are no essential carbohydrates: the body produces glucose itself through gluconeogenesis. A low-carbohydrate diet is therefore not superior—without plant sources, fiber, vitamins, and phytonutrients are also lost. “Not essential” does not mean “not useful.”

Why do people respond differently to starch?

People measurably differ in how their blood sugar responds to the same meal. Genetics, the gut microbiome, physical activity, and sleep all interact—the extent to which each factor matters remains unclear.

AMY1: varying numbers of copies of the amylase gene

The AMY1 gene encodes salivary amylase and occurs in varying copy numbers. According to Perry et al. (2007, Nature Genetics), populations with traditionally starch-rich diets have, on average, more AMY1 copies than groups with low-starch diets. Whether the copy number affects an individual’s blood sugar, weight, or disease risk is disputed—follow-up studies have produced conflicting results. It does not provide a basis for dietary recommendations.

Blood sugar response, the microbiome, and what this means in practice

Studies using continuous glucose monitoring show that the same standardized meal triggers blood sugar rises of varying magnitude in different people, sometimes in association with the gut microbiome. This does not mean that personalized dietary algorithms reliably work—many effects are smaller than the impact of more physical activity or fiber.

Your genes do not dictate a way of eating. The most practical personalization is the simplest: observe how you feel after certain meals. If a large white-bread breakfast makes you tired at eleven, that is useful information—without any lab tests.

When is a medical evaluation advisable?

Medical evaluation is advisable as soon as symptoms persist, worsen, or occur alongside warning signs.

Suspected diabetes or prediabetes

Severe thirst, frequent urination, unexplained weight loss, persistent fatigue, or wounds that heal poorly should be evaluated. Diabetes is diagnosed using fasting blood glucose, HbA1c, or an oral glucose tolerance test—not through self-observation or a genetic test. Even without symptoms, screening is advisable if you are significantly overweight, have a family history of type 2 diabetes, or previously had gestational diabetes.

Irritable bowel syndrome, FODMAPs, and intolerances

Recurring abdominal pain, bloating, and changes in bowel movements may indicate irritable bowel syndrome; short-chain carbohydrates (FODMAPs) worsen symptoms for some people. A low-FODMAP diet is a time-limited diagnostic tool, not a permanent diet. Blood in the stool, weight loss, fever, anemia, or onset after age 50 should be investigated promptly.

Bloating and diarrhea after eating fruit or drinking juice may be caused by fructose malabsorption; with dairy products, lactose intolerance may be responsible. The standard diagnostic method for both is a medical H2 breath test. mybody® does not offer a standalone test product for either condition—we prefer to state that clearly.

Get more context with mybody®

You can put all the essentials into practice without any test at all. If you also want to know which genetic predispositions related to carbohydrate metabolism are being discussed, you can use DNA analysis as additional information. mybody® (MYBODY Lab GmbH) offers the NutriCare | View the INFINITY DNA Test.

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Analysis of more than 140 genetic variations in 54 evaluations and 8 chapters across approximately 200 pages—including variants related to carbohydrate and energy metabolism. Also includes a personalized nutrition plan with recipes and more than 1,000 rated foods.

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To put it honestly: The test does not measure blood sugar, is not a diabetes test, and does not provide a diagnosis. It analyzes genetic variants, but says nothing about how your blood sugar is responding today—for that, laboratory tests are needed.

Equally honestly: The evidence for gene-based nutrition recommendations is mixed. It has often not been demonstrated that they improve health more than general recommendations. Such a test is an additional source of guidance, not a basis for making medical decisions.

Information on price, sample type, scope, and processing time comes from the mybody® product page (as of July 2026) and may change. A self-test does not replace a medical diagnosis.

Context: What a test can—and cannot—do

A DNA-based nutrition test can provide structure: it brings information together, provides a plan, and prompts many people to engage systematically with nutrition.

What it cannot do is measure a metabolic state. Genes do not change, whereas blood sugar, weight, and blood lipids do. Nor can a disease be genetically identified or ruled out—neither type 2 diabetes, irritable bowel syndrome, nor fructose malabsorption. Laboratory values, breath tests, and medical evaluation are needed for that.

And no test replaces putting it into practice. The greatest effect comes from the habits that follow: enough fiber, few free sugars, mostly minimally processed foods, and regular physical activity.

Conclusion

Carbohydrates are neither good nor bad. This nutrient group ranges from fiber in legumes to the sugar in soft drinks—evaluating these extremes as one category inevitably leads to contradictory statements.

The professional organizations largely agree: DGE: more than 50 percent of energy intake and at least 30 grams of fiber daily, EFSA: 45 to 60 percent, WHO: less than 10 percent free sugars, plus whole grains, vegetables, fruit, and legumes as preferred sources. Regarding weight, the 2022 Cochrane Review found only minimal long-term differences—the decisive factor is what you can sustain.

In practical terms: start with beverages, then fiber, then the degree of processing. Avoid lists of forbidden foods and moral judgments about food. Seek medical advice if symptoms persist or there is a suspicion of diabetes, irritable bowel syndrome, or an intolerance.

Frequently asked questions (FAQ)

Sources

1. German Nutrition Society (DGE): Reference Values for Nutrient Intake – Carbohydrates and Dietary Fiber.
2. World Health Organization (WHO), 2015: “Guideline: Sugars intake for adults and children” – recommendation to limit free sugars. who.int
3. World Health Organization (WHO), 2023: “Carbohydrate intake for adults and children: WHO guideline” – preferred sources of carbohydrates, vegetables and fruit, and dietary fiber. who.int
4. European Food Safety Authority (EFSA), 2010: “Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre.” efsa.europa.eu
5. Naude CE, Brand A, Schoonees A et al. (2022): “Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk,” Cochrane Database of Systematic Reviews, Art. No.: CD013334. cochranelibrary.com
6. Perry GH, Dominy NJ, Claw KG et al. (2007): “Diet and the evolution of human amylase gene copy number variation,” Nature Genetics. nature.com
7. IQWiG / gesundheitsinformation.de: Type 2 Diabetes—Causes, Consequences, Diagnosis, and Treatment. gesundheitsinformation.de

Carbohydrate and fiber intake are based on [1], free sugars on [2], preferred sources on [3], the 45 to 60 percent on [4], the diet comparison on [5], the deliberately cautious interpretation of AMY1 on [6], and diabetes diagnostics on [7]. The fiber values in the table are rounded reference values; product-specific information comes from mybody-x.com and may change.

mybody® Editorial & Expert Team

Nutritional Science Carbohydrate Metabolism Nutrigenetics Microbiome & Gut Science

This post was created by the mybody® editorial and expert team, which brings together expertise in nutritional science, nutrigenetics, microbiome and gut science, and laboratory diagnostics. Learn more about our team on our editorial and authors’ page.

Published on July 27, 2026 · Last updated on July 27, 2026

Medical notice: This post is for general information only and does not replace medical advice, diagnosis, or treatment. Dietary changes in the presence of existing conditions—especially diabetes, use of blood glucose-lowering medication, pregnancy and breastfeeding, or a history of eating disorders—should be undertaken with medical or nutritional guidance. If symptoms persist, please consult a doctor.