Lacking energy after lunch, ravenous hunger in the evening, concentration problems at work – even though the night was actually long enough? Many people experience exactly this interplay of high performance and a sudden slump almost every day. This is often not due to an acute lack of sleep, but possibly a blood sugar level that has become unbalanced.
Dr. Philipp Sabanas, general practitioner and head of Doctorum 2 in Vienna, explains in an interview why glucose, our body’s central energy source, reacts more sensitively than we are aware of, why strong fluctuations promote tiredness, irritability and cravings – and which everyday measures actually help to stabilize energy, concentration and mood in the long term.
Dr. Sabanas, what exactly is meant by the term blood sugar and what function does it perform as an energy supplier in the human body?
In medical terms, blood sugar – i.e. glucose – is the central energy source of our body. Every single cell is dependent on precisely this energy: the brain, the nervous system, the muscles. Depending on how high the energy requirement is – for example during physical exertion or intensive mental work – the need for glucose also increases. Without glucose, survival would not be possible.
Why is a stable blood sugar level so important for our daily well-being, our performance and even our mood?
Strong fluctuations lead to rapid drops in energy. This manifests itself in poor concentration, irritability, loss of performance and cravings. High insulin levels followed by low blood sugar levels are particularly problematic – this triggers real food cravings. Stable blood sugar, on the other hand, ensures consistent energy, mental clarity and physical performance.
What processes control blood sugar regulation in everyday life, and why do so many people today react sensitively to fluctuations?
The regulation is quite complex, in simple terms two hormones play the main role: insulin and glucagon. Insulin lowers blood sugar by enabling the cells to absorb glucose. Glucagon has the opposite effect and increases blood sugar by releasing glucose from the liver. Stress hormones such as cortisol and adrenaline also have a regulating effect. It is easy to explain why so many people react more sensitively today: the main causes are high sugar consumption, white flour products, frequent snacking, chronic stress, lack of exercise and lack of sleep. I see this in many patients.
At what fluctuations does one speak of an imbalance – and how does this manifest itself in concrete terms?
After a meal, blood sugar should rise slowly and then slowly fall again within about three hours. This is physiologically normal. We speak of an imbalance when the blood sugar rises very quickly and falls again just as quickly. Typical consequences are ravenous appetite, trembling, loss of concentration, tiredness and irritability. These symptoms are often diet-related, but are also exacerbated by stress and lack of sleep.
What role do readily available carbohydrates, sugar and highly processed foods play in chronic fatigue?
Sugar consumption has risen massively over the last 100 years. In the past, sweets were eaten on special occasions – such as Christmas or birthdays. Today, sugar is practically everywhere, even in products where you wouldn’t expect it. Industrialization has contributed significantly to this. This permanently high intake acts almost like a drug. At the same time, we are seeing an enormous increase in overweight and obesity. The constant availability and high consumption promote blood sugar fluctuations – and therefore also chronic fatigue.
Why do many people experience the typical afternoon slump?
A very carbohydrate-rich lunch can lead to a sharp rise in blood sugar. In combination with a sumptuous meal, this results in the well-known “midday coma”. Blood sugar rises quickly and then drops again rapidly – resulting in tiredness and a drop in performance.
How important are protein, fats and fiber for stable blood sugar levels – and are there practical guidelines?
A balanced diet is crucial. Not all fats are the same – high-quality fats are healthy and important for the body. Practical guidelines for a meal can be around 20 to 30 grams of protein, combined with moderate amounts of carbohydrates – ideally in the form of vegetables or high-fiber options. Fiber supports a slower rise in insulin. The goal is a moderate, not excessive blood sugar level.
How much does exercise affect blood sugar levels immediately after eating?
Exercise is extremely effective. Just 10 to 20 minutes of walking after eating can make a big difference. Climbing stairs or going for a walk is completely sufficient – you don’t need to run a marathon.
From a medical point of view, what helps sustainably against constant tiredness?
It is always a combination of several factors: a balanced diet, a regular eating rhythm, sufficient exercise and consistent stress and sleep management. If you stabilize these areas, you create the basis for a balanced blood sugar level – and therefore more energy in everyday life.
Our expert
Dr. Philipp Sabanas is an American-Austrian general practitioner and senior partner at Doctorum2 in 1020 Vienna. The primary care center was opened in January 2025 under the direction of Dr. Sabanas and Dr. Roman Spitzmüller and offers comprehensive general medical care. Dr. Sabanas places particular emphasis on nutritional advice and supporting his patients with diets.
Website: https://www.doctorum2.at
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