“Cut the sugar!” – that’s usually the first piece of advice we get when trying to lose weight, especially fat. The results after doing so can vary, but for many people, it ends in the yo-yo effect: we realize we can’t sustain a sugar-free lifestyle for long and fall back into old habits, often regaining the lost weight. But why does this happen? And are we really gaining weight only because of sugar?
What Are Sugars?
Sugars are part of a large group of macronutrients called carbohydrates, which are one of the three macronutrients our body needs—alongside fats and proteins. In our body, carbohydrates primarily serve as fuel (energy) for all types of cells—nerve, muscle, and even blood cells. They are not often used as building materials in the body, and they exist in small amounts (300–450g), stored mainly in the liver and muscles.
To understand their role and how they affect the body, we need to know the types of carbohydrates:
- Monosaccharides – the simplest sugars: glucose, fructose, and galactose – found in fruits, vegetables, and sweets.
- Disaccharides – sucrose (table sugar), lactose (milk sugar), and maltose.
- Polysaccharides – starch in plants or glycogen in animals and humans.
Why Is This Classification Important?
Sugar digestion starts in the mouth and continues through the digestive tract, but the most important part—absorption—occurs in the small intestine. Depending on the sugar type, the digestion process differs. Sugars must be broken down into monosaccharides to enter the bloodstream and be used for energy (ATP production). Enzymes like amylase and sucrase are required to break down complex sugars into simple forms.
What Does This Mean in Practice?
Peter, who has diabetes and uses insulin, sometimes experiences hypoglycemia (low blood sugar, <70 mg/dl or 3.9 mmol/l) after injections. He shakes, feels dizzy, and weak. To quickly recover, he carries a glucose gel. Glucose, being a monosaccharide, doesn’t need digestion and enters the blood directly—saving his life within minutes.
Michelle had a stressful morning and decided to eat a piece of cake her mother made, containing mostly sucrose and fat. An hour later, she felt tired again. Why? Sucrose (a disaccharide) breaks down into glucose and fructose, but quickly spikes blood sugar, prompting insulin to overcompensate, which leads to a blood sugar crash—and fatigue.
Anna had a potato salad for breakfast, full of polysaccharides and fiber. She felt heavy for two hours, but had stable energy throughout the day. Her meal was digested slowly, with a gradual release of glucose, avoiding sudden sugar spikes and crashes.
So, What’s the Problem?
The issue isn’t energy itself, but how quickly it’s absorbed and processed. Fast-absorbing carbs cause sudden crashes and hunger. That’s why you can’t eat more than two apples at once, but six Kit Kat bars go down easily.
Sugar Metabolism
Our body needs 1200–2000 kcal daily just for basic functions like breathing, heartbeats, and maintaining body temperature. Since 1g of carbs provides 4 kcal, this equals 300–500g of carbs/day. Fats offer more than double the calories—9 kcal/g. It’s recommended that 50–60% of our daily intake comes from carbs, about 250–300g/day for someone eating 2000 kcal.
After digestion, sugars enter the bloodstream as glucose. Insulin pushes it into cells for energy or stores it in the liver/muscles as glycogen (up to 300–450g). Excess glucose is stored as fat in fat cells (especially in the belly and hips) via a process called lipogenesis. Burning fat for energy takes longer and happens under specific conditions.
So, if you’re overweight, you have two options:
- Increase activity (e.g., exercise), or
- Decrease energy intake.
That’s easier said than done. Throughout human evolution, our species has faced various challenges. My great-grandfather probably never tasted chocolate. Someone from the Middle Ages in England had never seen a mango or a watermelon, and 10,000 years ago our ancestors didn’t know fruits and vegetables as we know them today. Until the development of the first civilizations in the Fertile Crescent, we didn’t know how to store food, nor did we have communities, let alone villages, cities, markets, refrigerators, shopping centers, or Uber Eats.
This means that whenever carbohydrates were found, our bodies urged us to consume as much as possible to create reserves, because we might have to walk tens of kilometers over the next few days without finding food. People who lived, say, a few centuries ago in Europe or North America, during winters and snowstorms, couldn’t just stumble upon fruits or vegetables—they simply weren’t available. Summer and spring were the seasons to eat plenty of carbohydrates in order to have reserves for the winter.
Since then, our genome has hardly changed, and we still hold on to those old habits. Our body still has the same “fear” of going days without food and “forces” us to consume sugar. “Eat that donut,” says our brain, fearing the future. This happens subconsciously—our subconscious doesn’t know we still have a big tub of ice cream in the freezer.
People with extra weight often understand that carbs contribute to fat gain but struggle to resist. This is natural. Hormones (ghrelin, leptin, cortisol, insulin), neurotransmitters (dopamine, oxytocin), social triggers (dinners, cinemas), and stress all play roles.
The Real Issue: Refined Sugars
A particular problem are the so-called processed sugars, which we do not naturally find in nature, such as sugary drinks, processed food, and sweets. They are deliberately designed to cause cravings, containing a lot of sugar and fat, with little or no fiber and micronutrients. These mainly consist of simple sugars that are absorbed very quickly, causing rapid spikes in blood sugar levels, followed by sudden drops, and our body then demands even more sugar.
We should not consume more than 20% of our total carbohydrate intake from processed sugars daily. So, for a person who needs 1000 kcal from carbohydrates per day, 200 kcal may come from processed sugars, which is about 50 g. That’s two Snickers bars.
Michelle, after two hours, needs more sugar because she feels like she’s out of energy. An extra piece of cake will raise her energy temporarily, but after that comes an even bigger crash—and so the cycle continues.
Eating sugar also triggers dopamine release as a reward, and our body says, “Great, I want to feel like this all the time.”
On the other hand, if we eat like Anna, we will generally have energy throughout the whole day and won’t experience these cravings, because the body says, “I don’t need extra energy, I already have enough,” and that way, overeating doesn’t happen.
What Can You Do to Avoid Overeating Sugar?
- Eat complex carbohydrates – they digest slowly and maintain steady energy.
- Combine carbs with fiber – fruits and vegetables contain natural sugars + fiber, slowing absorption.
- Control insulin levels – avoid rapid spikes through better food choices.
- Avoid constant snacking – frequent eating keeps insulin levels high, promoting fat storage.
- Try intermittent fasting – giving your body 16 hours without food reduces the opportunity to overeat.
- Manage dopamine triggers – we often eat out of boredom, especially while scrolling on our phones.
- Take daily walks – especially after meals, a 10-minute walk can improve sugar use.
- Combine carbs with protein – proteins increase satiety. For example, vegetables with 200g chicken breast improve nutrient use.
Conclusion
Do carbs make me fat? Yes—and no. As the biggest energy source, excess carbs can make you fat. They’re tasty and hard to resist, and you can eat them endlessly. But are carbs the only cause of weight gain? No. Still, they are the easiest path to fat gain.
Understanding the types of carbohydrates and balancing your intake is crucial for maintaining a healthy weight—or losing fat.
The Hungry Pharmacist 
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