Light as a drug: My big trip

Landing in another time zone means a big adjustment to our body clock. But Fenella Frost managed to beat jet lag by controlling her intake of light.

Fenella Frost on how she beat jet lag – using light


For most of us, knowledge about the non-visual effects of light on humans comes only from reading the latest research. While I have been presenting and writing about this research for years, true confidence in the science comes when you can prove to yourself that these theories work in your own real life.

Central to the research into these effects is an understanding of how light entrains our circadian rhythm, or body clock. A recent midwinter trip to Hong Kong gave me an opportunity to be my own guinea pig and put theory into practice.

The question was: Using light in the correct dose and at the correct time, could I rapidly shift my own body clock to avoid jet lag, and still function day to day? Could I force myself into a circadian phase that suited my needs?

Hong Kong is eight hours ahead of GMT and my flight was booked from Heathrow on Thursday evening at 10pm, arriving on Friday at 5.45pm local time. I had to work full days running up to the trip, and had a full programme of events in HK from Saturday morning, so I had to keep super sparkly and alert from 8am to 5pm every day in both time zones.

According to those who advise Nasa on jet lag, the key to controlling your circadian phase is getting lots of light during the day and as little as possible at night. The colour and amount of light are key to the efficacy of any circadian rhythm programme, (whether the programme is used to adjust or maintain the rhythm). My trip was during the dark British midwinter, so any light in my experiment would have to be electric. Three other tools helped me avoid light and stimulation: sunglasses, eye shades, ear plugs. I will admit I also used caffeine to really boost my programme.

Conventional wisdom says that after a long-haul journey, we should force ourselves to get up and function in the new time zone from the very start. New research, and our own experience, says that while this may work in some cases, it can also make it impossible for you to adjust as you may be exposed to light at completely the wrong time, and so shift your body clock in the wrong direction. For many people – sports stars, business executives or just tourists trying to make the most of their break, feeling your best immediately is highly beneficial.

The primary rule of circadian phase shifting is that light after 6pm will advance your phase (for travelling east) and light before 6am will delay your phase (for travelling west). Remember that this doesn’t mean 6am on your watch, it means 6am according to your body clock – as your body clock adjusts, so your plan must also adjust.

Obviously there are a lot of factors at play, but unless you’re a top sports star with a jet lag adviser on speed dial, this is a good basic rule. There are also lots of phone apps and gadgets (I used a wristband that monitored my activity and sleep) to help you create your own plan. Caffeine and exercise also help.


No weekend lie in today – alarm at 7am and all the lights on full as there is no daylight. Breakfast, strong coffee and a light workout. From 7pm I only used very low levels of lighting and avoided any screen time or caffeine. No trouble sleeping at 11pm.



Alarm at 6.30am, and to my surprise I was ready to wake up because my body believed it was 7am. All lights on full immediately and on to a normal work day. I avoided screens and kept lights dim from 6.30pm. Ready for sleep by 10.30pm.



I woke up before my alarm just before 6am, with my body believing that it was 7am. Lights on and a very early start at work with lots of coffee. Absolutely no screen time or caffeine after leaving the office and very dim lights. Asleep at 9.45pm – earlier than planned.



Awake again before the alarm at 5.30am, so used the gym with all the lights on full before work. Another productive day. I couldn’t wait until 1pm for lunch so gave in to hunger at 11.30am. Finished work promptly and packed bags during the evening under dim light. Struggled to stay awake until 9.30pm.



Wide awake at 4.30am, but waited until 5am to put all the lights on (just in case I unintentionally broke the 6am rule). At my desk by 7am and wanting lunch by mid-morning. Early dinner at work. At the airport in the evening,  I wore my darkest sunglasses (looking a bit like a rock star, except that I was flying economy). The 10pm flight boarded 30 minutes early, which suited me as I was now very tired. But Cathay Pacific followed conventional wisdom and kept the lights off for much of the second half of the flight so that people could sleep, and then put them all on full about 45 minutes before landing. This was the exact opposite of what I needed. So I told the cabin crew not to disturb me, put on my eye mask and ear plugs and fell soundly asleep before take-off. At 12.30pm (Hong Kong time) my wrist activity monitor woke me up as it had picked up my lighter phase of sleep. With several hours’ flying time to go, the plane was now in darkness with everyone asleep, so I went to the brightly lit bathroom and spent 10 minutes reading an eBook on my iPad, then tracked down some food and chatted to the cabin crew in their (brightly lit) kitchen.



After landing at 5.45pm, I headed to my sister’s apartment in central Hong Kong – she was shocked how I immediately slotted into her routine. We chose a dimly lit restaurant for dinner. 



My alarm woke me at 7am, which felt more like 5am. I put my sunglasses on, even inside, as it was before 6am in body clock terms. I felt great, having had a solid eight hours sleep and a strong coffee. At 10am I took off the glasses and made the most of the daylight to phase shift me even earlier. It was a busy day and I felt normal – no jet lag at all.



I had a lie-in according to my Hong Kong time watch and set my alarm for 7.30am. Again I had to avoid light for an hour until I was sure that my body clock was past 6am. I felt 100 per cent on local time.



I managed to continue performing 100 per cent in both locations, and – apart from the disruption of the flight itself – I had a full eight hours’ sleep every night, felt refreshed every morning and had no trouble falling asleep before or after the flight.

Light is a drug – use it wisely, take it as prescribed and make sure you complete the course.


  • Fenella Frost is group marketing and business development director at PhotonStar LED Group

  • Lux is hosting a special Lighting for Health and Wellbeing conference in London on Thursday 22 September. It’s free for all those associated with the management of buildings services. To view the details and register for a place, click on the conference logo .