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December 27, 2025
Dr. Andrea Gartenbach
Dr. Andrea Gartenbach is a specialist in internal and functional medicine and an expert in longevity. In the third part of her column on metabolic rhythm, she explains why training and protein are often not enough—and what the metabolism needs instead to work efficiently.
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Many people report persistent fatigue, stagnating training success, and noticeably slow recovery after exertion despite a protein-rich diet, regular exercise, and an overall health-conscious lifestyle.
This is irritating and often leads to the assumption that one must try harder, be more consistent, or train harder. However, the problem often lies elsewhere.
Our energy balance is a highly developed regulatory system. Its central task is to ensure survival and performance. For this, it continuously adapts to internal and external stimuli – such as movement, food intake, light, lack of sleep, or stress. These signals are processed through hormonal and neural control mechanisms, particularly through the autonomic nervous system, which unconsciously regulates heart rate, metabolic activity, and energy provision.
Simply put: In situations requiring activity, attention, and energy, the body ramps up its systems. Energy expenditure increases, stores are mobilized, and alertness rises. In phases of lower demands, these processes are throttled to save energy and enable regeneration.
The fundamental logic of this stimulus recognition and adaptation system is very old evolutionarily. In its core mechanisms, it differs little from the control processes of our early ancestors, when energy availability, movement, and rest were still closely linked to natural environmental conditions.
However, our daily life today follows different rules. Instead of clear stimuli, we experience a permanent overlap of small, sometimes contradictory impulses: persistent cognitive activation, frequent snacking between meals, evening light exposure from TV, laptops, and smartphones, as well as chronic stress. These factors influence central control variables of metabolism and recovery – including blood sugar regulation, insulin action, stress hormones like cortisol, and the nighttime release of melatonin, which is crucial for sleep quality and regenerative processes.
Each of these stimuli alone usually remains below a critical threshold. In combination, however, they create a persistent metabolic baseline activation. The body is simultaneously signaled to be ready for action, to process food, and to recover – a biologically almost unsolvable task.
In part 2 of our metabolism series, we saw how crucial muscles, protein intake, and insulin-like growth factor 1 (IGF-1) are for a stable metabolism. IGF-1 supports growth, repair processes, and the maintenance of muscle tissue. But neither muscles nor hormones respond to good intentions, discipline, or perseverance. They respond exclusively to biological signals.
The consequences of ambiguous signaling can be well observed in the laboratory. An example is cortisol levels. Cortisol should physiologically rise in the morning to initiate wakefulness, energy availability, and metabolic activation. If this rise is weakened or delayed, it indicates that the body has not received clear start signals.
Another common pattern: IGF-1 levels remain in the lower normal range despite adequate protein intake.
The body is not sick. It adaptively responds to a variety of contradictory messages.
Understanding this signaling mechanism makes it clear what metabolism still needs under modern conditions: clarity.
A reliable temporal rhythm that supports the circadian regulation of hormones, metabolic activity, and sleep-wake cycles. Sufficient gaps between meals. Quiet evening hours that signal the nervous system to transition from activation to recovery. Sleep that is as free as possible from night-time light exposure and digital stimuli. And a low level of inflammation that allows the mitochondria to efficiently produce energy instead of predominantly directing resources towards stress and defense processes.
These factors do not work in isolation but are interconnected. Sleep influences inflammatory processes, inflammation changes hormonal processes, and hormonal imbalances impede regeneration and performance. Conversely, if the system is relieved in one area, the whole benefits.
These prerequisites may seem unspectacular. However, they are crucial for the biological processes from part 2 to even take hold. A stable morning rhythm supports physiological cortisol dynamics and establishes the basis for metabolic flexibility. Longer intervals between meals facilitate fat burning and improve the utilization of consumed protein. An inflammation-low metabolism gives IGF-1 the space to fulfill its role as a growth and repair signal. And restorative night sleep creates the conditions the mitochondria need for maintenance, repair, and efficient energy production.
These changes have systemic effects. As soon as biological signaling is clear again, metabolism begins to work efficiently. Small causes can have large effects because biology is fundamentally economically organized.
For a well-functioning metabolism, we do not need to train harder or become more disciplined. What matters is whether our body receives clear and reliable signals. Only when rhythm, recovery, and metabolic relief work together again can the metabolism fulfill its actual task: providing energy efficiently instead of constantly compensating.
The three parts of this series ultimately tell a coherent story: Not about how to "optimize" metabolism, but about why it so often has to compensate today. Part 1 was about the changed conditions of our modern life, which put biological systems under constant tension. Part 2 showed how central muscles, protein utilization, and IGF-1 are for stability, adaptation, and regeneration. And Part 3 made it clear why all this only works when the body receives clear, reliable signals.
The common thread is simple and at the same time uncomfortable: Metabolism does not fail due to a lack of discipline or wrong decisions. It reacts to an environment that has become biologically contradictory. Constant activation without real breaks, energy supply without rhythm, recovery without darkness – all this forces the body into a mode where it protects instead of builds.
Modern metabolic health therefore does not begin with more effort but with more precision. With the understanding that biology responds to clarity, not perfection. If we learn to clearly separate stress and recovery again, to understand meals as a signal instead of a constant state, and to take sleep seriously as an active repair process, the system realigns. Not abruptly, not spectacularly, but reliably.
Perhaps this is precisely where the most important change in perspective lies: Metabolism is not a problem to be solved. It is an intelligent system that wants to be understood. And the better we speak its language, the less we have to work against it, and the more it can do for us.
Metabolism is not a system that wants to be optimized – but one that needs to be understood.
You can find all columns by Dr. Andrea Gartenbach here!
