CHRONO:MEDICINE – Détails, épisodes et analyse

In collaboration with the organizers of the 18th Congress of the European Biological Rhythms Society (EBRS) (taking place in Lübeck in Northern Germany from the 24th to 28th of August 2025), three congress speakers are interviewed to talk about their research. As the first spotlight, Prof. Michael Hastings (MRC Laboratory of Molecular Biology, Cambridge) talks about his research journey from circatidal rhythms in marine organisms to circadian and circaannual rhythms in mammals. Our main focus is on the neurochemistry within the central clock of the suprachiasmatic nucleus (SCN) enabling it to tell time. We discuss the most relevant factors that support the SCN in telling time, and what means the SCN has to synchronize other clocks within our body. With respect to melatonin, we discuss its role in sleep versus informing our body about the current season. We also talk about supplementing melatonin for specific populations. Lastly, Michael shares memories from attending previous EBRS congresses and why you should consider joining it this year.

Chapters:

(00:00:39) Introducing the EBRS 2025 spotlights

(00:03:51) Michael Hastings

(00:07:17) Circatidal rhythms

(00:14:38) The central clock or SCN

(00:24:47) Different zeitgebers

(00:35:17) Melatonin

(00:46:14) Melatonin as a sleeping aid

(00:51:38) EBRS congress experience

(00:58:22) Career advice

(01:10:02) Funny anecdote

(01:13:54) Outro

Studies that Michael refers to:

Reviews on circatidal rhythms

https://doi.org/10.1016/j.cub.2008.06.041

https://doi.org/10.1016/j.tig.2024.01.006

Prevalence of mutations in clock genes to make the period length shorter or longer than approx. 24 hours, rare familial sleep disorders

https://doi.org/10.1038/s41386-019-0476-7

Mice mutations support that the same enzymes are involved as in the human sleep disorders

https://www.nature.com/articles/s41583-018-0026-z

Period genes in the SCN are activated by light

https://doi.org/10.1016/S0092-8674(00)80494-8

Caffeine can phase shift the circadian clock

https://doi.org/10.1126/scitranslmed.aac5125

Manipulation of NPY and serotonin can shift the SCN clock

https://doi.org/10.1152/ajpregu.00320.2022

Human cortisol levels increase before awakening in anticipation of wake

https://doi.org/10.1677/JOE-07-0378

Temperature in the physiological range can act as a zeitgeber to entrain peripheral clocks

https://doi.org/10.1016/S0960-9822(02)01145-4

When interfering with neuropeptide levels within the SCN, you can entrain the SCN with temperature cycles

https://doi.org/10.1126/science.1195262

High levels of estradiol make the SCN run faster

https://doi.org/10.1126/science.557840

Melatonin is a transplacental zeitgeber

https://pubmed.ncbi.nlm.nih.gov/3780553/

https://doi.org/10.1177/074873049701200603

Martha Gillette and others applied melatonin to brain slides containing the SCN, showing that this could shift the SCN clock, the sensitivity of the SCN to this melatonin effect was found to occur during daytime (when melatonin is not released naturally)

https://link.springer.com/article/10.1007/s00441-002-0576-1

GWAS papers: variance of melatonin receptor are related to the type 2 diabetes andmetabolic disorders

https://www.nature.com/articles/ng.277

https://www.nature.com/articles/s41574-018-0130-1

Contacting Michael Hastings:

Homepage: https://www2.mrc-lmb.cam.ac.uk/group-leaders/h-to-m/michael-hastings/

Email: ⁠mha@mrc-lmb.cam.ac.uk⁠

EBRS homepage:

https://ebrs-online.org

In this second part, Dr. Christian Benedict (Department of Pharmaceutical Biosciences, Research and Pharmacology at Uppsala University, Sweden) explains how our sleep changes with aging and upon different challenges of adult life. We discuss the so-called gold-standard method for measuring sleep (Polysomnography, PSG) and how modern wearable technologies perform compared to PSG. In this context, Christian evaluates the potential value of measuring heart rate variability (HRV) to assess sleep quality. He also emphasizes the health threat through obstructive sleep apnea (OSA) and how to use simple self-monitoring technologies to determine if you may be affected by OSA yourself. Lastly, we acknowledge poor sleep as a general health risk but also discuss limitations and problems that can arise from overstating this.

Chapters:

(0:00:12) Intro

(0:02:20) Aging and sleep

(0:11:10) Polysomnography (PSG)

(0:22:25) Sleep wearables & HRV

(0:27:07) Obstructive sleep apnea

(0:33:10) Limitations of wearables

(0:36:41) Sleep across chronotypes

(0:44:50) Poor sleep as a health risk?

(0:55:19) Outro

Studies that Christian refers to:

Meta-analysis (2004) PSG data over the lifespan

https://pubmed.ncbi.nlm.nih.gov/15586779/

Paper on app findings of almost a million people asked on “how long do you sleep?”

https://pubmed.ncbi.nlm.nih.gov/36509747/

Studies on PSG vs. some commercial wearables ?

https://jcsm.aasm.org/doi/10.5664/jcsm.7128

Sleep apnea: Spotlight article with Jesse Cooks and Jonathan Cedernaes

https://pubmed.ncbi.nlm.nih.gov/33180697/

Lancet Respiratory Medicine review, 425 million people suffer from moderate to severeobstructive sleep apnea

https://pubmed.ncbi.nlm.nih.gov/31300334/

Ad-hoc sleep apnea screening in patients admitted to the hospital, 80% are not aware of it

https://pubmed.ncbi.nlm.nih.gov/19186102/

Australian study using a measurement pillow to track sleep apnea

https://www.atsjournals.org/doi/full/10.1164/rccm.202107-1761OC

Christian’s work (2015) those who have over 40 years regular sleep problems have an increased risk for Alzheimer’s

https://pubmed.ncbi.nlm.nih.gov/25438949/

Studies comparing people with kids and without kids, those with kids live longer

https://jech.bmj.com/content/71/5/424

How to contact Christian Benedict:

Email: Christian.benedict@farmbio.uu.se

LinkedIn: https://www.linkedin.com/in/christian-benedict-a25b1615a/

In the second part with Prof. Russell Foster (Head of the Nuffield Laboratory of Ophthalmology, and Director of the Sleep and Circadian Neuroscience Institute at the University of Oxford), contributing to the Daylight Awareness Week (13-17th of November 2023), we continue our discussion around the differential impact of daylight and electric light on health. We provide a historical perspective about human inventions that aimed to end the dependency on daylight - from fire to electric lighting. Prof. Foster further shares practical recommendations on how daylight and electric light can support health and well-being. Lastly, he gives an outlook on where the research around lighting and health is heading to in the future.

More information about the Daylight Awareness Week: ⁠https://daylight.academy/daylight-awareness-week-2023/

Chapters:

(0:00:00) Intro & Recap of Part 1

(0:02:36) History of inventing fire & candles

(0:08:22) Rise of electric light & disruption

(0:15:15) Sensitivity to light at night

(0:22:03) Dominance of LEDs nowadays

(0:23:07) Interim conclusion

(0:27:18) Practical recommendations for evening lighting

(0:30:37) Architectural dilemma with daylight

(0:33:12) Early birds vs. Night owls

(0:37:35) Jet lag

(0:40:10) Drug development for blind people

(0:42:11) Mimick seasonal changes in daylight

(0:45:29) Russell’s personal outlook

(0:55:02) Funny anecdotes

(0:59:26) Outro

Papers/books that Russell refers to:

A. Roger Ekirch's book: “At Day's Close”

Thomas Wehr's research on bimodal or polymodal sleep:

"In short photoperiods, human sleep is biphasic" (Wehr 1992)

https://doi.org/10.1111/j.1365-2869.1992.tb00019.x

Russell's group - investigation on international populations, night owls were missing morning light

"Chronotype and environmental light exposure in a student population" (Porcheret et al. 2018)

https://doi.org/10.1080/07420528.2018.1482556

Charles Czeisler’s group - full-intensity kindle watching for 4 hours for 5 nights

"Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness" (Chang et al. 2014)

https://doi.org/10.1073/pnas.1418490112

Prior light exposure of 500-600 lux during the day abolished the suppressing-melatonin-effect

"The effects of prior light history on the suppression of melatonin by light in humans" (Hebert et al. 2002)

https://doi.org/10.1034%2Fj.1600-079x.2002.01885.x

Harvard group: aged humans show decreased sensitivity to light

"Decreased sensitivity to phase-delaying effects of moderate intensity light in older subjects" (Duffy et al. 2007)

https://doi.org/10.1016/j.neurobiolaging.2006.03.005

Christian Cajochen’s work on alertness, blue light is most important

"High Sensitivity of Human Melatonin, Alertness, Thermoregulation, and Heart Rate to Short Wavelength Light" (Cajochen et al. 2005)

https://pubmed.ncbi.nlm.nih.gov/15585546/

Arti Jagannath's work on jet lag:

SIK1 deletion in mice and jet lag:

"The CRTC1-SIK1 pathway regulates entrainment of the circadian clock" (Jagannath et al. 2013)

https://doi.org/10.1016/j.cell.2013.08.004

Recent review on SIK:

"The multiple roles of salt-inducible kinases in regulating physiology" (Jagganath et al. 2023)

https://doi.org/10.1152/physrev.00023.2022

How to contact Russell Foster:

Email: russell.foster@eye.ox.ac.uk

As part of the Daylight Awareness Week (13-17th of November 2023), Prof. Russell Foster (Head of the Nuffield Laboratory of Ophthalmology, and Director of the Sleep and Circadian Neuroscience Institute at the University of Oxford) talks about the differential impact of daylight and electric light on health. In the first part, we cover the basics of how daylight has shaped life on Earth and how it changes over the course of a 24-hour day. Prof. Foster further explains how light sets our inner time, the so-called circadian clock, and how light can influence sleep, alertness, cognitive performance, cardiovascular and metabolic health.

More information about the Daylight Awareness Week: https://daylight.academy/daylight-awareness-week-2023/

Chapters:

(0:00:00) Intro & Daylight Awareness Week

(0:02:20) Topics of this episode series

(0:04:34) Introducing Russell Foster

(0:11:22) Evolution through daylight

(0:16:38) Physical properties of light

(0:26:02) Discovery of how light sets the circadian clock

(0:37:01) Central & peripheral clocks

(0:41:00) Melatonin is the darkness hormone

(0:48:05) Physiological modulation by light

(0:53:05) Outro & Teaser to Part 2

Russell Foster's recently published book: "Lifetime"

Papers/books that Russell refers to:

"Spectral Sensitivity Tuning in the Deep-Sea" (Douglas et al. 2003)

https://link.springer.com/chapter/10.1007/978-0-387-22628-6_17

J. N. Lythgoe's book: "The Ecology of Vision"

"Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus)" (Nelson & Takahashi 1991)

https://doi.org/10.1113/jphysiol.1991.sp018660

"Phase-dependent shift of free-running human circadian rhythms in response to a single bright pulse" (Honma et al. 1987)

https://link.springer.com/article/10.1007/BF01945525

"Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock" (Berson et al. 2002)

https://doi.org/10.1126/science.1067262

Russell's group to demonstrate the existence of retinal ganglion cells in mice:

"Melanopsin retinal ganglion cells and the maintenance of circadian and pupillary responses to light in aged rodless/coneless (rd/rd cl) mice" (Semo et al. 2003)

https://doi.org/10.1046/j.1460-9568.2003.02616.x

Retinal ganglion cells in the macaque:

"Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN" (Dacey et al. 2005)

https://www.nature.com/articles/nature03387

Skin of frogs, melanophores --> melanopsin

"Melanopsin: An opsin in melanophores, brain, and eye" (Provencio et al. 1998)

https://pubmed.ncbi.nlm.nih.gov/9419377/

VA opsin only in fish, not in mammals

"A novel and ancient vertebrate opsin" (Soni & Foster 1998)

https://doi.org/10.1016/S0014-5793(97)00287-1

Samer Hattar’s work: projections to the hypothalamus from melanopsin

"Central projections of melanopsin-expressing retinal ganglion cells in the mouse" (Hattar et al. 2006)

https://doi.org/10.1002/cne.20970

"Circadian photoreception in the retinally degenerate mouse (rd/rd)" (Foster et al. 1991)

https://link.springer.com/article/10.1007/BF00198171

"Neural Reprogramming in Retinal Degeneration" (Marc et al. 2007)

https://doi.org/10.1167/iovs.07-0032

"Suprachiasmatic nucleus in the mouse: retinal innervation, intrinsic organization and efferent projections" (Abrahamson & Moore 2001)

https://doi.org/10.1016/S0006-8993(01)02890-6

Martin Ralph's tau mutant hamster, restore rhythms to the period of the donor:

"Transplanted suprachiasmatic nucleus determines circadian period" (Ralph et al. 1990)

https://www.science.org/doi/abs/10.1126/science.2305266

Peripheral clocks concept shown by Uli Schibler's group in fibroblasts:

"Resetting of Circadian Time in Peripheral Tissues by Glucocorticoid Signaling" (Balsalobre et al. 2000)

https://www.science.org/doi/10.1126/science.289.5488.2344

Josephine Arendt melatonin pioneer:

"Melatonin as a chronobiotic" (Arendt & Skene 2005)

https://doi.org/10.1016/j.smrv.2004.05.002

Contradictory evidence for the use of melatonin to facilitate the onset of sleep

Example meta-analysis article: "Effects of exogenous melatonin on sleep: a meta-analysis" (Brzezinski et al. 2005)

https://doi.org/10.1016/j.smrv.2004.06.004

Patients on beta-blockers produce less melatonin:

"Influence of beta-blockers on melatonin release" (Stoschitzky et al. 1999)

https://link.springer.com/article/10.1007/s002280050604

How to contact Russell Foster:

Email: russell.foster@eye.ox.ac.uk

In the second part with Dr. Jorn Trommelen (Assistant Professor, Department of Human Biology, Maastricht University, The Netherlands), we talk about Jorn's recent study on pre-sleep protein ingestion after acute endurance exercise to stimulate muscle protein synthesis. Jorn explains how these findings from acute studies relate to boosting long-term gains in strength, hypertrophy and endurance performance in response to regular pre-sleep protein ingestion. Based on his studies, Jorn shares his view on practical recommendations for pre-sleep protein in endurance- and resistance-training types of sports.

Main paper that we discuss in depth:

Pre‐sleep Protein Ingestion Increases Mitochondrial Protein Synthesis Rates During Overnight Recovery from Endurance Exercise: A Randomized Controlled Trial (Trommelen et al. 2023)

https://link.springer.com/article/10.1007/s40279-023-01822-3

Additional papers that Jorn refers to:

Long-term study on pre-sleep protein for muscle gains:

Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men (Snijders et al. 2015)

https://pubmed.ncbi.nlm.nih.gov/25926415/

How to contact Jorn Trommelen:

Twitter: @JornTrommelen

Website: nutritiontactics.com

Instagram: @nutritiontactics

LinkedIn: https://www.linkedin.com/in/jorntrommelen/

Email: jorn.trommelen@maastrichtuniversity.nl

Dr. Jorn Trommelen (Assistant Professor, Department of Human Biology, Maastricht University, The Netherlands) talks about his research on pre-sleep protein ingestion after exercise to stimulate muscle protein synthesis. In the first part, we discuss the different forms of proteins and how endurance vs. resistance training differ in their post-exercise protein demand. Jorn further explains why the sleeping period is actually not so different from the awake period with respect to protein needs. We also dive into the details of the main methodological approaches used in Jorn's group to assess muscle protein synthesis.

Main paper:

Pre‐sleep Protein Ingestion Increases Mitochondrial Protein Synthesis Rates During Overnight Recovery from Endurance Exercise: A Randomized Controlled Trial (Trommelen et al. 2023)

https://link.springer.com/article/10.1007/s40279-023-01822-3

Additional papers that Jorn refers to:

Yves Boirie, guy who invented the cow model

First study about production of the labeled milk:

Production of large amounts of [13C]leucine-enriched milk proteins by lactating cows (Boirie et al. 1995)

https://pubmed.ncbi.nlm.nih.gov/7815181/

First paper applying the model:

Slow and fast dietary proteins differently modulate postprandial protein accretion (Boirie et al. 1997)

https://pubmed.ncbi.nlm.nih.gov/9405716/

Paper from Jorn's group applying the model:

Ingestion of Free Amino Acids Compared with an Equivalent Amount of Intact Protein Results in More Rapid Amino Acid Absorption and Greater Postprandial Plasma Amino Acid Availability Without Affecting Muscle Protein Synthesis Rates in Young Adults in a Double-Blind Randomized Trial (Weijzen et al. 2022)

https://pubmed.ncbi.nlm.nih.gov/34642762/

Jorn's review on this model:

Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects (Trommelen et al. 2021)

https://pubmed.ncbi.nlm.nih.gov/33487181/

Literature for peak times in myofibrillar vs. mitochondrial protein synthesis after exercise:

"Whereas myofibrillar protein synthesis rates are typically highest during acute post-exercise recovery (0–6 h) [28, 29], mitochondrial protein synthesis rates appear to peak at ~ 24 h of post-exercise recovery [25, 27, 30]. Therefore, it could be speculated that post-exercise protein ingestion may prove to be more effective at stimulating mitochondrial protein synthesis rates when assessed over a more prolonged recovery period [31]."

!See numbered references in the main paper stated above!

Generally 20g of protein maximally stimulates muscle protein synthesis:

Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men (Moore et al. 2009)

https://pubmed.ncbi.nlm.nih.gov/19056590/

Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise (Witard et al. 2014)

https://pubmed.ncbi.nlm.nih.gov/24257722/

Presleep dietary protein-derived amino acids are incorporated in myofibrillar protein during postexercise overnight recovery (Trommelen et al. 2018)

https://pubmed.ncbi.nlm.nih.gov/28536184/

Studies of protein’s impact on sleep

Protein intake and its effect on sleep outcomes: a systematic review and meta-analysis of randomized controlled trials (Wirth et al. 2023) https://academic.oup.com/nutritionreviews/article/81/3/333/6694939?login=true

Protein Ingestion before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial (Kouwe et al. 2017)

https://pubmed.ncbi.nlm.nih.gov/28855419/

How to contact Jorn Trommelen:

Twitter: @JornTrommelen

Website: nutritiontactics.com

Instagram: @nutritiontactics

LinkedIn: https://www.linkedin.com/in/jorntrommelen/

Email: jorn.trommelen@maastrichtuniversity.nl

In the second part with Prof. Frank Scheer (Division of Sleep and Circadian Disorders, Brigham and Women's Hospital at Harvard Medical School, USA), we discuss what a night-shift worker could consider doing acutely (preceding, during, and following a shift) and chronically (when working years of shift schedules) to minimize health risks. In this context, we consider concepts like "sleep banking", when to exercise, caffeine ingestion, what to eat, light exposure strategies & more. We highlight which practical tools are supported by scientific evidence, whereas others seem promising but require further investigation. Lastly, Frank shares his view on how this research field around the health risks of shift work could in the long run achieve guideline changes for shift workers and how labor sectors that are dependent on shift work could be stimulated to improve working conditions.

Literature underlying practical recommendations:

Banking Sleep: Realization of Benefits During Subsequent Sleep Restriction and Recovery (Rupp et al. 2020)

https://academic.oup.com/sleep/article/32/3/311/3741695

Interplay of Dinner Timing and MTNR1B Type 2 Diabetes Risk Variant on Glucose Tolerance and Insulin Secretion: A Randomized Crossover Trial (Garaulet et al. 2022)

https://doi.org/10.2337/dc21-1314

Effects of caffeine on human behavior (Smith 2022)

https://doi.org/10.1016/S0278-6915(02)00096-0

Blue-blockers reduce melatonin suppression:

Blue Blocker Glasses as a Countermeasure for Alerting Effects of Evening Light-Emitting Diode Screen Exposure in Male Teenagers (van der Lely et al. 2014)

https://www.jahonline.org/article/S1054-139X(14)00324-3/fulltext

Rods and cones also play a role for light suppression on melatonin etc.

S-cone contribution to the acute melatonin suppression response in humans (Brown et al. 2021)

https://onlinelibrary.wiley.com/doi/full/10.1111/jpi.12719

Circadian Photoentrainment in Mice and Humans (Foster et al. 2020)

https://www.mdpi.com/2079-7737/9/7/180

Exercise mitigates sleep-loss-induced changes in glucose tolerance, mitochondrial function, sarcoplasmic protein synthesis, and diurnal rhythms (Saner et al. 2021)

https://doi.org/10.1016/j.molmet.2020.101110

Prior Exercise Lowers Blood Pressure During Simulated Night-Work With Different Meal Schedules (Fullick et al. 2009)

https://pubmed.ncbi.nlm.nih.gov/19556971/

Impact of the human circadian system, exercise, and their interaction on cardiovascular function (Scheer et al. 2010)

https://www.pnas.org/doi/full/10.1073/pnas.1006749107

Timing of Moderate-to-Vigorous Physical Activity Is Associated with Improvements in Glycemic Control in Type 2 Diabetes in the Look AHEAD Study (Qian et al. 2022)

https://doi.org/10.2337/db22-537-P

Heart attacks are more common in the morning:

Circadian Variation of Ambulatory Myocardial Ischemia: Triggering by Daily Activities and Evidence for an Endogenous Circadian Component (Krantz et al. 1996)

https://doi.org/10.1161/01.CIR.93.7.1364

How to contact Frank Scheer:

LinkedIn: https://www.linkedin.com/in/frankscheer/

Email: FSCHEER@BWH.HARVARD.EDU

Prof. Frank Scheer (Division of Sleep and Circadian Disorders, Brigham and Women's Hospital at Harvard Medical School, USA) introduces us to the topic of shift work and its adverse effects on many health aspects. We define the different forms of shift work with a particular focus on night shifts by painting a picture of what the everyday life of a typical nurse in the hospital looks like, and how working night shift possibly affects her health acutely and in the long term. Thereby, we cover the diverse side-effects of shift work on our physiology and cardiometabolic system as well as associated pathologies. After this general overview, we dive into two recent clinical studies performed by Frank Scheer’s group which focus on the question at what times a shift worker could eat or fast to lower the health burden.

Correction by Frank Scheer:

"The Medical Chronobiology Program was already founded in 2005, not 2015."

Main papers that we discuss in depth:

Daytime eating prevents internal circadian misalignment and glucose intolerance in night work (Chellappa et al. 2021)

https://www.science.org/doi/10.1126/sciadv.abg9910

Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity (Vujovic et al. 2022)

https://www.cell.com/cell-metabolism/pdfExtended/S1550-4131(22)00397-7

Additional papers that Frank and I refer to:

Adaptation of the circadian rhythm of 6-sulphatoxymelatonin to a shift schedule of seven nights followed by seven days in offshore oil installation workers (Gibbs et al. 2002)

https://doi.org/10.1016/S0304-3940(02)00247-1

Adaptation of the melatonin rhythm in human subjects following night-shift work in Antarctica (Midwinter & Arendt 1991)

https://pubmed.ncbi.nlm.nih.gov/2027519/

Energy Expenditure and Changes in Body Composition During Submarine Deployment—An Observational Study “DasBoost 2-2017” (Rietjens et al. 2020)

https://www.mdpi.com/2072-6643/12/1/226

The Relationship between Working Night Shifts and Depression among Nurses: A Systematic Review and Meta-Analysis (Okechukwu et al. 2023)

https://pubmed.ncbi.nlm.nih.gov/37046864/

Circadian misalignment increases mood vulnerability in simulated shift work (Chellappa et al. 2020)

https://www.nature.com/articles/s41598-020-75245-9

Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota (Chellappa et al. 2022)

https://pubmed.ncbi.nlm.nih.gov/34861073/

Review articles on shift work and health risks:

Impact of circadian disruption on glucose metabolism: implications for type 2 diabetes (Mason et al. 2020)

https://pubmed.ncbi.nlm.nih.gov/31915891/

Impact of Circadian Disruption on Cardiovascular Function and Disease (Chellappa et al. 2019)

https://pubmed.ncbi.nlm.nih.gov/31427142/

Health consequences of circadian disruption (Sletten et al. 2020)

https://academic.oup.com/sleep/article/43/1/zsz194/5699236?login=true

Effects of circadian disruption on the cardiometabolic system (Rüger & Scheer 2009)

https://link.springer.com/article/10.1007/s11154-009-9122-8

The endogenous circadian system worsens asthma at night independent of sleep and other daily behavioral or environmental cycles (Scheer et al. 2020)

https://www.pnas.org/doi/abs/10.1073/pnas.2018486118

The two-process model of sleep regulation: Beginnings and outlook (Borbely 2022)

https://onlinelibrary.wiley.com/doi/full/10.1111/jsr.13598

Controlling for sleep as a factor in the negative effects of shift work, circadian misalignment is above and beyond sleep-disruptive effects:

Circadian Misalignment Augments Markers of Insulin Resistance and Inflammation, Independently of Sleep Loss (Leproult et al. 2014)

https://diabetesjournals.org/diabetes/article/63/6/1860/34298/Circadian-Misalignment-Augments-Markers-of-Insulin

Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans (Morris et al. 2015)

https://www.pnas.org/doi/abs/10.1073/pnas.1418955112

Adverse metabolic and cardiovascular consequences of circadian misalignment (Scheer et al. 2009)

https://www.pnas.org/doi/abs/10.1073/pnas.0808180106

Shift work studies in mice by Carolina Escobar:

Food Intake during the Normal Activity Phase Prevents Obesity and Circadian Desynchrony in a Rat Model of Night Work (Salgado-Delgado et al. 2010)

https://academic.oup.com/endo/article/151/3/1019/2456529

Shift Work or Food Intake during the Rest Phase Promotes Metabolic Disruption and Desynchrony of Liver Genes in Male Rats (Salgado-Delgado et al. 2013)

https://doi.org/10.1371/journal.pone.0060052

Timing of food intake predicts weight loss effectiveness (Garaulet et al. 2013)

https://www.nature.com/articles/ijo2012229

How to contact Frank Scheer:

LinkedIn: https://www.linkedin.com/in/frankscheer/

Email: FSCHEER@BWH.HARVARD.EDU

Dr. Cas Fuchs (Department of Human Biology, Maastricht University, The Netherlands) talks about two of his studies in which he separately investigated the effect of cold- versus hot-water immersion after exercise on recovery. In this context, Cas explains the acute physiological response to cooling and heating. We question what athletes claim or hope to achieve by applying cooling and heating strategies in practice and whether there is scientific evidence behind these claims. The primary focus of Cas' studies is how cooling and heating influence muscle protein synthesis after resistance training and he describes how muscle protein synthesis is measured in his research group. Based on his studies, Cas shares his practical recommendations on who might want to incorporate cooling or heating into his/her exercise routine with specific goals in mind.

Main papers that we discuss:

Postexercise cooling impairs muscle protein synthesis rates in recreational athletes (Fuchs et al. 2019)

https://physoc.onlinelibrary.wiley.com/doi/full/10.1113/JP278996

Hot-water immersion does not increase postprandial muscle protein synthesis rates during recovery from resistance-type exercise in healthy, young males (Fuchs et al. 2021) https://journals.physiology.org/doi/full/10.1152/japplphysiol.00836.2019

Additional papers that Cas and I refer to:

Review on the muscle protein synthesis approach:

The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance-Type Exercise (Trommelen et al. 2019)

https://link.springer.com/article/10.1007/s40279-019-01053-5

Studies on lowering pain after exercise through the cold:

Cold water immersion and recovery from strenuous exercise: a meta-analysis (Leeder et al. 2019)

https://paulogentil.com/pdf/Cold%20water%20immersion%20and%20recovery%20from%20strenuous%20exercise%20-%20a%20meta-analysis.pdf

Cold to maintain workload in sets:

Water Immersion Recovery for Athletes: Effect on Exercise Performance and Practical Recommendations (Versey et al. 2013)

https://link.springer.com/article/10.1007/s40279-013-0063-8

Postexercise cold water immersion benefits are not greater than the placebo effect (Broatch et al. 2014)

https://pubmed.ncbi.nlm.nih.gov/24674975/

More long-term studies on cold water immersion on muscle mass and strength being lower (group from Australia):

Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training (Roberts et al. 2015)

https://pubmed.ncbi.nlm.nih.gov/26174323/

Previous study on muscle inflammation markers after cooling, but found no differences:

The effects of cold water immersion and active recovery on inflammation and cell stress responses in human skeletal muscle after resistance exercise (Peake et al. 2016)

https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP272881

Cold on the muscle clock in mice:

Time-of-Day Effects on Metabolic and Clock-Related Adjustments to Cold (Machado et al. 2018)

https://www.frontiersin.org/articles/10.3389/fendo.2018.00199/full

How to contact with Cas Fuchs:

Twitter: @27CJ

Email: cas.fuchs@maastrichtuniversity.nl

Prof. Alexandra Johnstone (The Rowett Institute, University of Aberdeen, Scotland) talks about her recent study on the timing of calorie loading and its differential effects on weight loss and appetite control. Alex thereby investigated mechanisms behind the diet concept of "eating breakfast like a king". We further discuss the real-world implications of her findings and practical considerations for when to eat most of your calories for different populations.

Main paper that we discuss: Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity (Ruddick-Collins et al. 2022) https://www.cell.com/cell-metabolism/fulltext/S1550-4131(22)00344-8

Additional papers that Alex and I refer to:

Timing of food intake predicts weight loss effectiveness (Garaulet et al. 2013)

https://www.nature.com/articles/ijo2012229

High Caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women (Jakubowicz et al. 2013)

https://onlinelibrary.wiley.com/doi/10.1002/oby.20460

Feeding rodents during light hours makes them obese compared to feeding them during the dark period:

Circadian Timing of Food Intake Contributes to Weight Gain (Arble et al. 2009)

https://onlinelibrary.wiley.com/doi/full/10.1038/oby.2009.264

Circadian component on the thermic effect of food:

Circadian Rhythms in Resting Metabolic Rate Account for Apparent Daily Rhythms in the Thermic Effect of Food (Ruddick-Collins)

https://doi.org/10.1210/clinem/dgab654

Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity (Vujovic et al. 2022)

https://doi.org/10.1016/j.cmet.2022.09.007

Impact of Meal Timing and Chronotype on Food Reward and Appetite Control in Young Adults (Beaulieu et al. 2020)

https://www.mdpi.com/2072-6643/12/5/1506

James Bett's definition of breakfast is “within 2-3hours after waking”:

Is breakfast the most important meal of the day? (Betts et al. 2016)

https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/is-breakfast-the-most-important-meal-of-the-day/74DC8BF20CAF1D7D5E75CD46A35451F8

German bunker studies:

Human circadian rhythms: a multioscillatory system. (Aschoff & Wever 1976)

https://europepmc.org/article/med/786739

How to contact Alex Johnstone:

Twitter: @Dr_A_Johnstone

Email: alex.johnstone@abdn.ac.uk