Why Weight Loss Is Not Linear
Weight loss comes in waves, not a straight line: cut calories and the body slows metabolism to defend its stores — a plateau is adaptation, not failure.
Energy balance is a real physical law, but the body does not work as a linear machine. Hormonal and neural mechanisms defend energy stores: when calorie intake drops, the body slows metabolism, intensifies hunger, and reduces spontaneous movement — this is adaptive thermogenesis. Modern living conditions erase natural rhythms: artificial light, a constant room temperature, continuous access to food, and a low movement load. As a result, the body can stay in a sustained storage mode. Fluctuating weight loss is not a failure — it is biological adaptation.
Weight loss fluctuates – the story of energy balance and biological adaptation
Energy balance does work: if you take in more energy than you use over the long run, your body weight rises. But when you cut calories, the body responds: metabolism slows, hunger increases, and spontaneous movement falls. Because of this, weight loss is not a smooth process but a sequence of cycles.
Seasonal metabolic rhythm contributes to this in part. Changes in day length shift the melatonin[G] rhythm, which through the hypothalamus[G] may affect hunger hormones and energy expenditure — an effect observed mainly in animal studies and arctic populations. Epidemiological data show that many people do gain weight in winter, but this is explained mainly by reduced physical activity and increased holiday calorie intake, not by photoperiod-driven changes in metabolic rate. The seasonal effect exists, but in urban, obese patient populations it is not the main driver of weight-loss stagnation.
Temperature also influences metabolism. In the cold, brown adipose tissue (BAT) can activate and non-shivering thermogenesis appears — a phenomenon well documented in human PET studies (Saito et al., 2009; van Marken Lichtenbelt et al., 2009). The caloric impact in adults, however, is modest: activated BAT typically burns on the order of 100–300 kcal/day at peak cold exposure, and compensatory appetite often cancels longer-term weight effects (Carpentier et al., 2018). In metabolic syndrome and obesity, the amount and activity of functional BAT are further reduced. BAT-targeted interventions (cold exposure, capsaicin, mirabegron) have not yet reached proven weight-loss status clinically. BAT activation is therefore an adjuvant, secondary tool in a weight-loss strategy, not a primary driver — regular movement and a stable meal rhythm are more reliable and more evidence-based tools for improving metabolic flexibility.
Why does weight loss stall? Adaptive thermogenesis and the traps of modern life
The modern lifestyle interrupts these signals. Constant artificial light shifts the melatonin rhythm[G]; physical inactivity impairs glucose utilization and reduces insulin sensitivity[G]. The body can remain in a “summer storage mode” all year round — leading to chronic insulin resistance.
This helps explain seasonal body-weight fluctuation. We have already mentioned the effects of reduced activity, higher calorie intake, and shorter daytime light exposure. In seasonal affective disorder, appetite and carbohydrate cravings rise. This is not a lack of willpower but a conflict between biological rhythm and environment.
The composition of the gut microbiota[G] and the short-chain fatty acids (SCFA[G]) it produces vary according to diet and lifestyle. A monotonous, processed-food-heavy modern diet reduces the variety of substrates available to the microbiota, which over the long term may affect SCFA[G] production and metabolic balance. A direct link with insulin sensitivity[G] in humans is likely, but the causal relationship is not fully proven [143].
Work with your biology – rhythm, microbiota, and sustainable body weight
Energy balance works best when hormonal regulation and the microbiological environment support it. A diet rich in protein and fiber, stable meal timing, regular movement, and microbiota[G] support improve insulin sensitivity[G]. Natural daylight and Zone-2[G] movement are especially effective from this perspective.
This is why the MicroBiome Run program does not push rapid dietary changes. It provides a system: a stable daily rhythm, the right nutrient composition, and microbiota[G] support. Once these are in place, the effect of energy balance also shows up.
If weight loss stalls or you gain weight in winter, that is not a failure. It is your body’s seasonal adaptation. Light, temperature, movement, and the microbiota[G] all influence it — and all can be tuned.
Summary of the 3-day goal: to understand that energy balance matters but is not the sole determinant; the hormonal environment and food quality also influence how body weight changes. The first energy-density[G]-based meal pattern takes shape.
- 3-day Lifestyle Journal completed with energy-density[G] tagging
- Every meal contains a protein source and a fiber source
- Eating window ≤12 hours
- ≥6,100 steps/day
- Daily fluid target of at least 1.7 liters (2×200 ml in the morning, at least 900 ml during the day, 2×200 ml in the evening)
Why does the process stall? The main causes of stagnation and cycles:
- Adaptive thermogenesis: In response to a calorie deficit, the body lowers basal metabolic rate, increases hunger (rising ghrelin[G], falling leptin[G]), and reduces spontaneous physical activity. This is well documented in the Biggest Loser phenomenon.
- Temperature and light signals: Constant artificial light shifts the melatonin rhythm[G]. Brown adipose tissue (BAT) in adults — especially in MetSyn and obesity — is limited in both amount and activity; the maximum caloric effect is on the order of 100–300 kcal/day (Carpentier et al., 2018), and compensatory appetite often cancels it out. BAT activation is therefore an adjuvant, secondary intervention, not a primary weight-loss strategy. Stable daytime light exposure and ordering the circadian rhythm[G] are clinically more reliable tools.
- Microbiota[G] and metabolism: SCFA[G]-producing bacteria need substrate (fermentable fiber). Reduced dietary diversity and a high proportion of ultra-processed foods can dampen SCFA[G] production, which may affect appetite signaling and insulin sensitivity[G].
- Seasonal effect: In winter, activity drops and calorie intake rises — this is the most common cause of weight-loss stagnation, not photoperiod-driven metabolic change. The existing seasonal rhythm is not the cause of failure, just the context.
Treatment strategy:
- Restore biological flexibility: break the sustained “storage mode”.
- Light and heat: morning sunlight (or light therapy) is the primary tool; moderate cold exposure is an optional adjuvant element to activate BAT, but is not sufficient on its own.
- Eating window: a stable 10–12 hour window to restore insulin rhythm.
- Zone-2[G] movement: low-intensity activity that directly supports fat oxidation.
“Calories matter, but not alone. Food quality also steers your hormones. Stable energy → stable appetite.”
- Lifestyle Journal: next to every food, mark low / medium / high energy density[G] (0/+/++) using the description above
- Every meal includes protein + fiber (e.g., meat/eggs + vegetables)
- Record the eating window (time between first and last meal)
- 20-minute walk after a meal
- Mental task: “When did I eat calories without satiety?” — note 2–3 specific examples.
- 3 main meals, no continuous snacking
- Every meal: protein + fiber + fluid
- Skip ultra-processed foods for 1 day
- Step count ≥6,100
- Mental task: look at yesterday’s list — what do the foods that left you quickly hungry have in common? (energy density[G]? lack of fiber? lack of protein?)
- High-protein breakfast (≥25 g protein)
- Avoid late-night eating
- 10-minute walk after meals
- Slightly increase fiber intake
- Mental task: “When was my energy level stable?”
- body weight (kg)
- meal times and contents
- post-meal walk (Y/N)
- daily protein (g)
- energy density[G]: (0/+/++)
- NOVA[G] level;
- sleep quality (1–5)
- hunger scale (1–5)
- step count;
- bedtime / wake time (00:00–23:59 format)
- stool Bristol (1–7);
- bloating
- daily stool count (occurrences)
- fluid intake (l)
- UltraBiome dose (1/2/3 caps)
- LOT identifier;
Energy density[G] indicates how many calories are contained in a unit mass of a food. For example:
- Low (0): salad, tomato, cucumber, soups, cooked vegetables
- Medium (+): chicken breast, fish, eggs, legumes, fruits
- High (++): bread, rice, cheese, nuts, sweets, fried foods
The goal is not to forbid high-energy-density[G] foods but to recognize them — so you know when you are eating a lot in a small volume.
- These 3 days stabilize the insulin response, appetite signaling, glucose variability, gut motility[G], and the nutrient supply to the microbiota[G].
References
[143] Tremaroli V, Bäckhed F. Functional interactions between the gut microbiota and host metabolism. Nature. 2012. Link
Review of mechanisms by which the gut microbiota influences host metabolism, with implications for obesity, cardiovascular disease and metabolic syndromes including type 2 diabetes. The microbiota modulates host metabolic pathways by improving energy yield from food and by altering dietary and host-derived compound bioactivity. Better mechanistic understanding will support the development of metabolic-disease treatments targeting the microbiota.