March 15, 2026, 4:28 pm | Read time: 12 minutes

The per capita consumption of sugar in Germany in 2023 was 90 grams of sugar per day.^.1 However, according to the World Health Organization (WHO), the recommended amount of sugar per day should be less than 50 grams.^.2 This corresponds to five to ten teaspoons of sugar. Now, we don’t usually shove sugar into our mouths by the spoonful—it’s mainly hidden in processed products. This makes it difficult for us to properly assess how much we are really putting into our bodies. Or do you think of sugar spoons when you drink sugar-sweetened drinks or fruit juices? Self-assessment and reality are likely to diverge when it comes to sugar consumption if you don’t take a close look at it. A figure from the German Nutrition Society provides a clue: in order not to overdo it with sugar, every German would have to reduce their sugar consumption by at least 25 percent.^.3 So it’s not unlikely that you and I have too much sugar in our system … But how can you tell? Cologne-based nutritionist Uwe Schröder explains.

What Happens in the Body When You Eat Sugar (in Normal Quantities)

When you eat sugar, your body goes through a series of processes that have short-term and long-term effects.

• Immediately after consumption, the sugar enters the bloodstream, causing blood sugar levels to rise
• Our pancreas releases insulin so that our cells can absorb the sugar and convert it into energy. Sugar in the cells is right and important, because our body needs it there for countless vital functions.
• The high blood sugar level must be regulated again: This is the job of
• insulin’s antagonist: glucagon, a so-called simple sugar, does the job.
• Tadaa: The blood sugar level drops again. Everything is fine!
• Sugar doesn’t just work in the blood and cells: even before the food reaches our stomach, it activates the so-called dopaminergic system in the brain. It is responsible for reward and motivation in the upper brain and temporarily increases the dopamine level after sugar intake. The dopamine released reinforces the behavior that led to the reward. Now we want more sugar! And: the dopamine actually makes us work really hard to get a reward^.4

This Is What Happens When You Eat Too Much Sugar on a Permanent Basis

The more sugar we consume, the harder it is for our body to store it in our cells. If large amounts of sugar are constantly flowing into the body, our cells become blunted against insulin. In medical terms, this is known as reduced insulin sensitivity. The ability of our body cells to respond to the hormone insulin at all decreases. To put it simply: the sugar knocks, but no one inside opens up.

Impending Insulin Resistance

This type of insulin resistance usually develops gradually over many years. In fact, the pancreas can withstand the overproduction of insulin for a surprisingly long time; genetic predisposition plays a major role. If it stops producing insulin at some point, diabetes mellitus develops. The pancreas no longer produces insulin. The sugar floats around in the blood. This makes the urine “sweet”—diabetes mellitus does not mean “sweet urine” for nothing. Type 2 diabetes is usually diagnosed late. It usually occurs after the age of 40. Remission is possible, but a cure is not. Those affected have to take tablets and—in advanced stages—also insulin. On average, they die five to ten years earlier than people without metabolic disease. In Germany, 6.7 million people have the disease. The trend has been rising for years^.5

Obesity

There is another effect: it is well known that eating large amounts of sugar in the long term not only makes us metabolically ill, but also causes us to put on weight. Why do we put on weight if the flow of sugar doesn’t stop? Our body stores excess sugar as glycogen or, if the corresponding stores are full, in the liver. Too much sugar can cause the liver cells to become fatty. This is the reason for the risk of a non-alcoholic fatty liver and general fat storage: the body builds up fat—instead of breaking it down.

Reward center

You have probably already noticed what long-term, high sugar consumption does to the brain: We become downright addicted, needing more and more sugar to satisfy our reward center. One study has shown, for example, that the dopaminergic system is particularly active when test subjects eat pudding that is particularly high in sugar and fat^.6

Is Sugar Causing More Problems Today Than in the Past?

As mentioned, the number of people diagnosed with diabetes mellitus has been rising for years. This is despite the fact that we have never been more aware of the risks than we are today and new drugs are constantly being developed. So why is this? Cologne-based nutritionist Uwe Schröder argues that it is due to society’s increasing lack of exercise. “Studies show that most people are moving less and less,” says Schröder. As a result, they have fewer and fewer sugar stores in their muscles and consequently less use for the sugar. The liver therefore converts it into fat instead. Schröder warns of what he sees as a major problem: “There are studies that show that almost 30 percent of all people in Germany already have signs of fatty liver disease.”

According to Schröder, this figure is as high as 40 percent for people over the age of 50. However, the combination of too little exercise and too many carbohydrates (primarily sugar) is the main risk of fatty liver.

“If I Use Sugar as Muscle Fuel, It’s Necessary”

According to Schröder, who sits on the board of the German Institute of Sports Nutrition, the maximum daily dose of sugar also depends on how much exercise you do. “If you regularly engage in intense physical activity, you can of course eat a lot more carbohydrates (and therefore also sugar, editor’s note) than without physical activity.” This builds up muscle stores that can be used as a direct source of energy. It is not possible to pin down a specific figure, i.e. how much more, for physically active people. Schröder says: “If I use sugar as muscle fuel, it is necessary.”

“I need about five grams of glucose per hour for the brain to work, for the red blood cells and for the nerve cells – in other words, the organs and systems that are dependent on blood sugar in the short term.” That would be 120 grams a day. That much? That would be 70 grams more than the WHO and DGE recommendation. We remember: it was a maximum of 50 grams of sugar a day.

Schröder explains why the official recommendation still applies. As the body can also produce the 120 grams of glucose it needs from other nutrients, such as protein, it is not necessary to get all of it from food—in the form of refined sugar. However, the WHO’s sugar recommendation is about precisely this proportion.

For a general understanding of why the WHO’s 50 grams of sugar per day is exactly right, Schröder uses the energy requirement as a whole to deduce that sugar should make up a maximum of ten percent of total energy. “Let’s assume I consume 2000 kilocalories a day. Ten percent of that would be 200 kilocalories. One gram of carbohydrates has about four kilocalories. So that would be a maximum of 50 grams of sugar a day.”

“Absolute Upper Limit for Someone Who Does Little Exercise”

However, the nutritionist qualifies the WHO recommendation somewhat: “In my opinion, these 50 grams of sugar per day are the absolute upper limit for someone who does little exercise.”

7 Signs That You Are Eating Too Much Sugar

The signs of too much sugar consumption are very individual and varied. For example, skin blemishes, tiredness, frequent thirst or headaches can be symptoms that we have too much sugar in our system. The following seven signs are among the best known and—in the long term—also the most harmful.

1. Poor Insulin Levels and Blood Sugar Levels

The blood sugar level may still be normal, but the body already needs a lot of insulin to keep the blood sugar level so low (we are in the pre-diabetic range here). Uwe Schröder recommends having your fasting blood sugar level checked by a doctor. But that is only one point. “Most health insurance companies don’t pay for this, but we recommend also having your insulin levels checked.”

Another option would be to measure your blood sugar level several times a day with a meter from the pharmacy, just like a diabetic. “Then you can see whether the blood sugar level remains significantly elevated for a very long time after a high-sugar meal. If this is the case, you’ve eaten so much sugar that your cells are dulled,” says Schröder to FITBOOK. However, if the blood sugar level drops again and again, you still react sensitively to insulin. Blood sugar and insulin levels are therefore reliable indicators of whether you are consuming too much sugar and how high the risk of type 2 diabetes could be.

2. Obesity and Fatty Liver

Unsurprisingly, too much sugar in combination with too many other carbohydrates can lead to obesity. But that’s not all: the storage of the sweet substance in the liver can also lead to a fatty liver. Schröder recommends seeing a doctor if you suspect a fatty liver. A doctor can detect the first signs of a fatty liver during an ultrasound scan and have the liver values determined. “If you have altered liver values even though you are not an alcoholic and are not taking any medication, this indicates changes in the liver that may be due to sugar metabolism,” says the nutritionist.

3. Food Cravings

Another symptom of too much sugar can be cravings following the immediate consumption of sweets. “You react very well to this, but it can be a kind of psychological addiction to sugar when cravings occur,” warns Schröder. He recommends keeping a record of when you have consumed sugar and sugary foods during the day. In this case, it is ideal to take “insulin breaks,” i.e., to have as long a gap as possible between two sugary meals. “This doesn’t mean that you shouldn’t eat anything in between, but the meals should be more protein- and fat-heavy.” The aim is to keep insulin levels low over a long period of time.

4. Intestinal Problems

Constipation, diarrhea, flatulence, irritable bowel syndrome, leaky gut: according to Schröder, intestinal problems are the classic symptoms of long-term high sugar consumption. Overdoing it with sugar feeds bad gut bacteria and yeast fungi such as Candida, while good gut bacteria are suppressed. We add good bacteria such as lactobacilli and bifidobacteria to our intestines when we eat natural yoghurt, kefir, bread drink or fresh sauerkraut (fermented!).

5. Weakened Immune System

“There are sugar substances that come from intestinal bacteria and pass directly through these open areas in the intestinal wall, so-called lipopolysaccharides. These irritate the immune system, to which it reacts strongly,” says Schröder. Sugar also plays a role for some blood cells. If it is constantly present in high concentrations in the blood, “the energy metabolism can no longer function as well”.

6. Mental Blocks and Forgetfulness

Consistently high sugar consumption can cause concentration problems and is associated with what is known as central nervous insulin resistance. In this case, the brain cells lose their insulin sensitivity. If the brain reacts less well to insulin, it does not get enough glucose—despite high blood sugar levels. This can lead to mental blocks, mental exhaustion and mood swings. Studies suggest that insulin resistance in the brain promotes memory problems and can even increase the risk of Alzheimer’s in the long term^.7

7. Tooth Decay

Finally, the well-known sign of excessive sugar consumption, tooth decay. Toothache or visible cavities are actually a sign of advanced tooth decay. It is better to know the early signs: White or brown spots on the teeth. They are signs that the enamel is beginning to demineralize. If you are very sensitive to hot, cold, sweet or sour drinks and/or food, this can also be a sign of tooth decay.

More on the topic

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In large quantities Not just alcohol! 6 things that are harmful to the liver

Early warning signs of insulin resistance

Schröder names the following as early warning signs of insulin resistance:

• Lack of energy, especially after carbohydrate-rich meals
• Cravings
• Increase in visceral fat
• Concentration and attention problems

Reduce Sugar Consumption: “Consume as Little Corn Syrup as Possible!”

Pay attention to the ingredients when buying food if you want to reduce your sugar consumption. Ketchup and many sauces have a relatively high sugar content. Sugar is now even added to sausages and gherkins. “This also occurs in many alternative vegan or vegetarian products. This is because sugar has a flavor component and is a filler,” explains Schröder. Consumers should also consume as little corn syrup (glucose-fructose syrup) as possible. It is often found in soft drinks, ready-made products and sweets. This sweetener, which is widely used in the USA, is easy to produce but contains a lot of fructose. Fructose is metabolized exclusively in the liver—too much of it leads to an overload. Corn syrup, especially high-fructose corn syrup (HFCS), promotes insulin resistance and thus type 2 diabetes and increases the risk of obesity, among other things.