Post-holiday fatigue: understanding low energy levels and boosting your vitality
In January, many of us feel exhausted, drained, and lacking in energy. Is there really a link between winter and low energy levels? What are the reasons behind this feeling? Is Blue Monday a marketing myth, or is there a real dip in mood during winter?
Why we feel more tired in winter (and especially after the holidays)
Spoiler alert: Winter fatigue is not "all in your head": it is based on several well-documented mechanisms.
1) Less light = a disrupted biological clock
In winter, exposure to natural light decreases. However, light is a major signal for synchronizing the circadian rhythm (sleep/wake cycle). When this signal is missing, some people experience a shift in their sleep patterns (falling asleep later, difficulty waking up) and feel more drowsy and have lower energy levels. This mechanism lies at the heart of biological explanations for winter fatigue and seasonal affective disorder.
2) Less restful sleep (and post-holiday "sleep debt")
The holiday season often involves late nights, early mornings, travel, screen time, heavy meals, and more. The result is often sleep debt and "social jet lag" (the difference between weekday and weekend rhythms), both of which are associated with circadian dysregulation and an impact on immunity and recovery.
3) Alcohol ≠ quality sleep
Alcohol may seem to help you fall asleep, but it alters your sleep patterns and tends to reduce the quality of the second half of the night (fragmentation, less restful sleep). The next day, fatigue, mental "fog," and decreased motivation are common.
4) Rich meals: postprandial inflammation and energy slump
Meals that are very fatty and/or very sweet can trigger an unfavorable postprandial response (oxidative stress, inflammatory markers, temporary decline in endothelial function), which can contribute to feelings of heaviness and low energy—especially when this is repeated over several days, as is often the case during the holiday season.
“Blue Monday”: myth or reality?
1. The origin: a publicity stunt, not a scientific discovery
“Blue Monday” is generally presented as “the most depressing day of the year” (often the third Monday in January, which will be January 19 in 2026). But the idea comes from a marketing campaign associated with a formula that has been widely criticized as unscientific.
2. What we can honestly say
- No, science does not validate the existence of a universal "most depressing day" that can be calculated using an equation.
- Yes, January can be difficult for many people, but for mundane and variable reasons: lack of rest during the holidays, returning to work, gloomy weather, low light, sleep debt, financial constraints, unrealistic goals, etc.
Our tips for staying fit in winter
1) Take care of your sleep (top priority for combating fatigue)
Lack of sleep or poor sleep quality is one of the leading causes of fatigue.
Health authorities recommend:
regular bedtimes and wake-up times,
avoiding alcohol and stimulants in the evening,
getting enough sleep according to one's needs.
2) Get some natural light every day
Daylight is essential for regulating the biological clock (sleep/wake cycle).
In winter, the lack of light can increase drowsiness and low energy levels.
Even on gray days, going outside every day helps you wake up more easily and improves alertness.
3) Exercise regularly, even moderately
Regular physical activity helps to:
reduce fatigue,
improve sleep quality,
maintain energy on a daily basis.
It is not necessary to engage in intensive sports: daily walking and reducing the amount of time spent sitting are already beneficial.
4) Eat a balanced diet and stay hydrated
A varied diet and regular meals help to limit fatigue.
Dehydration, even mild, can also increase feelings of tiredness.
Our PharmaSmile tips for boosting your vitality in winter
As part of post-holiday winter fatigue, certain PharmaSmile dietary supplements can be incorporated into your routine to help support energy levels.
Formula combining vitamin C, vitamin D3, zinc, and echinacea extract to contribute to the normal functioning of the immune system and reduce fatigue.
Our vitamin C uses liposomal encapsulation technology that contributes to the stability of the vitamin in the antioxidant formulation, helping to protect cells from oxidative stress and reduce fatigue.
A combination of essential multivitamins and minerals, this dietary supplement is designed to support nutritional intake and help reduce fatigue.
A combination of chelated magnesium, taurine, and vitamin B6, which help reduce fatigue and contribute to the normal functioning of the nervous system.
These dietary supplements are part of a healthy lifestyle and should not replace medical treatment or a balanced diet.
Conclusion
Winter fatigue after the holidays is not inevitable: it can be explained by well-identified mechanisms such as lack of light, sleep deprivation, overeating, and returning to a busy schedule. Even though January can be more physically and mentally challenging, the famous "Blue Monday" actually has no scientific basis.
To regain energy in winter, the key factors remain: quality sleep, daily exposure to natural light, regular physical activity, and a balanced diet with adequate hydration.
In addition to these basics, some of our dietary supplements PharmaSmile can support you during this period by providing nutrients that are beneficial for normal bodily function and reducing fatigue.
Sources and references
Hannah K. Dollish, Mariya Tsyglakova, Colleen A. McClung, Circadian rhythms and mood disorders: Time to see the light, Neuron, Volume 112, Issue 1, 2024. https://www.sciencedirect.com/science/article/pii/S0896627323007109
Faraut B, et al. Immune disruptions and night shift work in hospital healthcare professionals: The intricate effects of social jet lag and sleep debt. Front Immunol. 2022 https://pmc.ncbi.nlm.nih.gov/articles/PMC9509137/
Katie S McCullar, Altered sleep architecture following consecutive nights of presleep alcohol, Sleep, 2024 https://pubmed.ncbi.nlm.nih.gov/38205895/
Ian M Colrain, et al. Alcohol and the Sleeping Brain, Handb Clin Neurol, 2018 https://pmc.ncbi.nlm.nih.gov/articles/PMC5821259/
Mazidi et al. (2021), Meal-induced inflammation: postprandial insights from the Personalized Responses to Dietary Composition Trial (PREDICT) study in 1,000 participants, ScienceDirect, 2021 https://www.sciencedirect.com/science/article/pii/S0002916522004269
Health Insurance – Fatigue: the right reflexes (ameli.fr)
https://www.ameli.fr/assure/sante/themes/asthenie-fatigue/bons-reflexes-cas-faut-consulter
Department of Health – Sleep and biological rhythms (sante.gov.fr)
https://sante.gouv.fr/prevention-en-sante/sante-des-populations/sante-environnementale/article/sommeil
ANSES – Physical activity and health
https://www.anses.fr/fr/content/activite-physique-et-sante
