the Body Clock Guide to Better Health

Listening to the pulse of your own rhythms.

The Body Clock Guide to Better Health – How to use your body’s natural clock to fight illness and achieve maximum health (2000) by Michale Smolensky and Lynn Lamberg

1. It’s about TIME

p5-6 “We report evidence from studies at leading medical centers worldwide showing that:

  • Many illnesses disrupt body rhythms.
  • The signs and symptoms of many illnesses vary across the twenty-four-hour day over the month, and around the year.
  • Time of day patterns help identify causes of many illnesses.
  • Chronotherapy, or timed treatment, aims to correct these underlying causes or reduce their adverse impact.
  • Glitches in the body clock itself may undermine health.
  • The time of day you take diagnostic tests or undergo medical procedures alters the results.
  • Time-of-day norms are known for many rhythms.
  • The time you take medicine matters.
  • Nondrug treatments may help correct underlying disturbances in the body clock.
  • How you organize your daily life, with respect to sleep, meals, exercise, and other factors may make  symptoms better or worse, and hasten or slow your recovery.

p9 “…the way your body absorbs, uses, and excretes drugs varies over the day. The same dose of medicine may be too much at one time, and too little at another. It may not even work at all.”

2. Your body is a Time Machine

p13 “In any one person, in all of us, body temperature, blood pressure, pulse and breathing rates, concentrations of hormones in the blood, hand dexterity, sensitivity to pain, and all other bodily functions differ markedly over the twenty-four-hour day. These variations are not random. They occur in synchrony with our habitual daily pattern of activity and rest.”

The Best of Times

p19 “Drug studies typically are conducted in the daytime for the convenience of both scientists nd subjects. Tests often begin early in the morning so they can be completed by the end of the normal workday. Ludicrous as it may seem, even some sleeping pills undergo testing this way.”

4. How Your Body Clock Works

p33 “The time at which the body is most sensitive to light comes when body temperature is lowest, around 4 AM to 5 AM.”

p35 “Signals from the eyes travel on two pathways to the brain in humans and other animals. Conscious vision travels by one route, and circadian vision, the other… Some blind people also function well on a twenty-four-hour day. They may not consciously recognize light, but still may receive circadian clock-setting light information…”

p36 “Light tells us it is daytime. The hormone melatonin tells us it is night. both day- and night-active species secrete melatonin mainly in the dark.”

“Melatonin is produced by the pea-sized pineal gland just behind the hypothalamus. Dusk tells the SCN to tell the pineal to turn melatonin secretion on, and at dawn to turn it off. We secrete melatonin longer in the long nights of winter, and for a shorter time in the short nights of summer. Changes from day to day alert animals that days are growing shorter or longer and, if they breed only in certain seasons, that it is the right or wrong time to breed. Melatonin may play a role in human reproduction, too.”

5. Are You a Lark, an Owl, or a Hummingbird?

[note: Lark = early bird, owl = night owl, hummingbird = in between, in a ratio of 1:2:7]

p41 “Some of us think of ourselves as night people, but humans can’t truly claim the night as home territory. We are programmed to function best in the daytime. We can’t see in the dark.”

“Lark and owl traits influence many aspects of daily life, including when we feel most alert, or when we sleep best. These traits determine when we most enjoy meals, exercise, sex, and other activities.”

p48-9 How Larks and Owls Differ




Most alert (self-report) Around noon Around 6 PM
Most productive (self-report) Late morning Late morning and late evening
Most active Around 2:30 PM Around 5:30 PM
Best mood Between 9 AM and 4 PM Steady rise from about 8 AM to 10 PM
Temperature highest Around 3:30 PM Around 8 PM
Age Most persons over age 60 Most college students and twentysomethings
Bedtime Go to bed two hours earlier than owls; fall asleep faster More variable bedtimes, stay up later on weekends and holidays
Waketime Awaken at desired time Awaken about same time as larks on workdays, 1-2 hours later on days off
Use of alarm clock Don’t need it Need multiple alarms
Temperature lowest Around 3:30 AM Around 6 AM
Quality of sleep Lifelong: sleep more soundly; wake up more refreshed, usually 3.4 hours after temperature minimum, daily low point on body clock Lifelong: get less sleep wake up sleepier, usually 2.5 hours after temperature minimum
Nap Rarely Take more and longer naps; fall asleep more easily in daytime
Mid-sleep time Around 3:30 AM Around 6 AM
Favorite exercise time Morning Evening
Peak heart rate Around 11 AM Around 6 PM
Lowest heart rate Around 3 AM Around 7 AM
Mood  Mood declines slightly over day Mood rises substantially over day
Morning behavior Chatty Bearish
Evening behavior Out of steam Full of energy
Mealtimes Eat breakfast 1-2 hours earlier than owls Often skip breakfast; eat other meals at same times as larks on workdays, 90 minutes later on days off
Favorite meal Breakfast Dinner
Daily caffeine use Cups Pots
Personality More introverted?(still debated) More extroverted?(still debated)
Shift-work adaptability Work best on day shifts Work best on evening shifts; tolerate night and rotating work better
Travel More jet lag Adapt faster to time-zone changes, particularly going west
Peak melatonin secretion About 3:30 AM About 5:30 AM

7. A Good Night’s Sleep

p66 “It is increasingly clear that good sleep, and enough of it, is critical for both mental and physical health.. Too little sleep has wide-ranging ill effects.”

p67 “Missing sleep lowers the body’s production of natural killer cells, an important part of our self-defense system. … To fight infections, we produce chemicals called cytokines that make us feel sleepy.”

p70 “Sleep gates open and shut roughly every 90 to 120 minutes… Sleep gates explain why you may find it hard to fall asleep if you go to bed early.”

p77 “When people are tired, Donald Blimise notes, they eat more, and they eat more often.”

p77-9 Timewise Tips for Good Sleep

  • regularize your schedule
  • Program yourself to sleep with daily rituals
  • Keep your bedroom dark, or wear eyeshades
  • Keep your bedroom quiet
  • Keep your bedroom cool
  • go to bed only when sleepy
  • Reserve bed and bedroom for sleep and sex
  • If you can’t fall asleep within thirty minutes, get out of bed
  • If you nap, limit time lying down to thirty minutes in midafternoon
  • Take a hot bath ninety minutes before bedtime
  • Exercise regularly
  • Avoid caffeine within five hours of bedtime
  • Don’t drink alcohol or smoke near bedtime
  • Learn relaxation techniques

9. Fitness by the Clock

p92 ” How strong you are, how fast, how accurate, how flexible, how quick-witted, how focused, and how able you are to keep going are among the numerous factors that vary over the day, some modestly and others markedly.”

“Exercising at the times your body is most suited for it has many pluses: you’ll perform better, be less likely to get hurt, and probably enjoy it more.”

“As a general rule, physical performance is best, and the risk of injuries least, in late afternoon and early evening.”

10. Time to Eat

p110 “Body rhythms call for different mixes across the day of the three essential macronutrients: carbohydrates, proteins and fats.”

11. Time for Sex

p122 “Among both married and single heterosexual couples, sex is most frequent on the eighth day of the woman’s menstrual cycle, counting from the first day of menstruation.”

“Sexual desire and fantasies in women peak about a week later, at mid-cycle, when they ovulate.”

p123 “Although popular culture links spring with romance, people have sex most often in the fall. This is true for the population as a whole, despite vacations, religious practices that either encourage or discourage sex, and similar events that may alter the frequency of sex for some individuals and groups.”

Menstrual Cycle Clock

p128 “Light exposure, crucial for strong daily rhythms, also may ensure menstrual regularity.”

“Evidence that fertility rates are lower in areas where people spend most of their time indoors suggest light’s importance. … Fertility rates are higher closer to the equator, where daylight hours are longer, than in far northern latitudes.”

“[Menstruation] starts sooner in girls who live at sea level than in those who live at higher altitudes, with higher light intensity. First menstruation also shows an annual pattern. It begins most often in the late fall and early winter, particularly in girls who live in rural settings, suggesting a tie to changing day length.”

13. Clockwatching at Work

p166-8 “…research suggests how sleep loss may have contributed to some of the twentieth century’s most grievous industrial catastrophes.”

  • the crisis at Three Mile Island nuclear power plant
  • the Exxon Valdez spill
  • the space shuttle Challenger explosion
  • the meltdown and explosion of a reactor at the Chernobyl nuclear plant
  • the chemical disaster in Bhopal, India

14. A Time to Heal

p193-4 “Charting your own body rhythms is a good first step in health maintenance and disease prevention. You need only a few simple tools.”

With a pencil and paper you can chart

  • your mood across the day
  • your alertness across the day
  • your wake/sleep cycle, and the time and type of disturbances of sleep
  • what you eat and when you eat it
  • symptoms of pain, fatigue, urinary frequency, etc…

With a wristwatch you can chart

  • your heart rate
  • your breathing rate

With a thermometer you can chart

  • body temperature over the day
  • body temperature across your menstrual cycle

With a blood pressure cuff

  • blood pressure over the day”

the Worst of Times

Health Around the Year

301 Days to Dec 21st 2012


Comments are closed.

%d bloggers like this: