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Nutritional Anthropology's Bible:
Looking at our genetic programming is a powerful technique for identifying the optimum way to feed ourselves. This same technique can be applied to other aspects of our lifestyles too. One of these is exercise. What is our genetic programming for exercise?
the millions of years of evolution, what were the patterns of physical
activity practised by our species?
will that tell us about the amount of exercise we should be getting
we can work out a lot about the physical activity of our Pleistocene
ancestors. First of all we know how they must have foraged for food, how
far they travelled, how fast, and even their muscular development.
by studying contemporary forager tribes, we can see how they organised
themselves on a daily basis.
typical Pleistocene group consisted of thirty-five to forty five people,
roughly equally divided between men and women. This group would camp in
one place for a few days and then move on make another camp 10 to 20
miles away. They carried very little with them, but they still had to
walk all the way! They moved, not for the fun of it, but because they
had to. The terrain would be open savannah-type grassland in the tropics
of East Africa.
camped, each day the group would split up to forage for food. The women,
children and old men went off in one party, foraging for roots, fruits,
tubers, berries and easily caught bugs and animals. This party, on
average covered about 5 miles. They leisurely walked and rested from
time to time. After about four to five hours they were done. The
children walked too and, a lot of the time, scampered about and chased
each other as well as the lizards and beetles. Babes in arms of course
is estimated that the average adult female energy expenditure was 600
kcal per day on physical activity. This compares to 230 kcal for
today’s sedentary female office worker.
able-bodied men went off, chiefly looking for small game, but would also
be collecting other edible matter on an opportunistic basis. This party
would cover more ground during the day - 9 to 12 miles on average. Part
of the time they would be running or jogging, to chase and trail
potential game. Most of the time, they too would be finished after about
four to five hours. However on rarer occasions they may be away for as
much as 48 hours tracking a wounded animal.
is estimated that their daily expenditure of energy was over a 1,000
kcal. Compare this to the 306 kcal of the average sedentary male office
are therefore two patterns, one for each gender:
would pass their lives exercising to a moderate extent, and low
started their lives with the female pattern, graduated to the masculine
pattern for most of their lives (vigorous and more sustained physical
activity) and then tapered off to feminine levels again in old age.
does this chime with what we know about human biology today? It fits
very well. Evidence is that women do not need to exercise so long or so
hard as men to maintain their health. Men need more vigorous physical
activity to maintain health. From the world of track athletics we know
that men are better built for endurance running.
happened to our ancestors in old age? What is striking is that old
people stayed physically active until their very last days. They were
athletes right to the end. The end would come when they could no longer
keep up with the group when it moved camp some 10 miles away. The infirm
person would be left behind, propped up under a bush, to await the
arrival of the jackals and other predators. In this harsh existence,
there was no room for people who put the survival of the group at risk.
what are we to make of this? Everything we know about peoples or
individuals who get this amount of physical activity demonstrates that,
as a result, they have better health than they would otherwise have had.
Note the qualification ‘than they would otherwise have had’.
Exercise by itself is not enough. Other lifestyle activities can be even
more important in determining good health, notably non-smoking and good
big question is, are there any vital body functions that depend
on physical activity? Yes, indeed there are. Studies, going from those
on bed-ridden people to astronauts, all point to a number of conditions
brought about by a lack of physical activity. We are not like the bear
for example that can stay immobile for 6 months (while hibernating)
without suffering health consequences.
are the consequences for human health then, of physical inactivity?
Let’s look at some of them.
and Health Factors
demineralisation and fractures
condition is multi-faceted, but all the evidence suggests that regular
physical activity improves bone structure, its volume and thereby
resistance to fracture. Elderly women can benefit from as little as one
hour per week of lower-intensity activity - 42% lower risk of hip
fracture and 33% lower risk of vertebra fracture.
The rhythmic jolting associated with walking/jogging, excites the bone
building cells (osteoblasts) into raising their tempo. In young people
the bone builders work faster than the bone strippers and bone mass
increases. Even in older people the bone builders will work harder and
fall less far behind the bone strippers.
arthritis and joint stiffness
activity of the kind practised by our Pleistocene ancestors encouraged
cartilage maintenance, lubrication and renewal of the wearing surfaces.
Dysfunctional joints are due in large part to not giving them enough to
do. If you don’t use it, you lose it!
is the collective name given to a quarto of ‘diseases of civilisation’:
high blood pressure, coronary artery disease, obesity and diabetes. They
all have a common link - high insulin levels. Yes, our old nemesis of
insulin rears its ugly head. Low exercise levels mean that more insulin
has to be secreted to handle a given glucose load. Result: more insulin
floating around creating mischief. (See Chapter Five.) Exercise is
essential to maintain optimum resistance to diabetes, obesity,
hypertension and heart disease.
is an artery that passes through the ball of the foot. As you walk or
run this artery gets alternately compressed and released. The general
effect is that of a pump. Walking/running helps pump blood through the
lower leg. Without it the lower leg gets poor circulation and is prone
to deep vein thrombosis.
you one of those people who, after a little while sitting at a desk or
table, find their knees jogging up and down? This too, is a natural
reflex helping to maintain lower leg circulation.
handmaiden to our blood circulation, we have a secondary system of
circulation, known as the lymphatic system. This is responsible, in
part, for transporting the products of digestion to other parts of the
body; bringing immune system killer cells to parts of the body under
attack and flushing away debris and toxic matter. Unlike the blood,
which is pumped around the body by the heart, the lymphatic system does
not have a pump of its own. It relies on the general flexing of muscles
to do the job. Lack of physical activity means sluggish lymphatic
circulation and a host of maladies linked to that.
are all, every single one of us, descended in an unbroken chain of
ancestors who have all successfully found a mate and reared their
children. Couples who got together to have children and didn’t, failed
for a number of reasons. Accidents, sickness, infertility all take their
toll. But the bottom line is that they didn’t have any offspring.
follows that we are descended from people who have been successful in
having children. They were successful because they were lucky and
because they were healthy. Not much can be done about luck, accidents
and so on, but over the long term our ancestors will have been slightly
better at picking healthy mates. We are programmed to recognise a healthy prospective mate. That, to a large
extent, is the substance of the ‘chemistry’ that sparks between two
people who are attracted to each other. ‘Looking good’ is an
important part of successful human reproduction.
if you are not looking for a mate, ‘looking good’ gives pleasure to
others. Film stars make their fortunes out of people’s hunger to cast
their eyes on good looking people. The exact nature of the good looks
changes with the mood of the times, but the fundamentals do not. No one
is going to make it as a heart throb if they are giving off an air of
general ill health. Glowing complexion, vibrant muscle tone and an
energetic demeanour are attractive in their own right. We are
genetically programmed to find them so.
the world of our ancestors, they did a lot of walking and running
because they had to. It was a matter of survival. It was the means by
which they got their dinner. If they were unsuccessful in getting
dinners they became dinner for
today’s world such automatic sanctions for lack of physical fitness
are rare. It is quite possible to live a lifetime as a couch potato and
never be embarrassed by a situation where your physical abilities are
found wanting. But just think about this: in an air crash, do you want
to be the last one to get out of the emergency door?
carefully controlled Finnish studies
over many years on identical twins have demonstrated what many people
have long suspected, that physically fit people live longer than those
who are not.
this study, it was found that in any given period, ‘Sedentary’
people were 1.3 times as likely to die as the ‘occasional’
exercisers and nearly twice as likely to die as the ‘conditioning’
exercisers. The figures were the same for both men and women.
exercise criteria were extremely modest
exercisers exercised for a minimum of 30 minutes, 6 times a month.
exercised even less than the ‘conditioners’ but did some regular
people claimed not to exercise at all.
do not know the effect on longevity if regular physical activity is
raised to the level of our prehistoric ancestors, but the suspicion has
to be that it is yet further improved.
depression and mood
evidence is now confirmed by an understanding of human biochemistry.
Physical exercise has a beneficial effect on a whole range of hormones
that regulate mood.
modulates hormones that act on serotonin receptors helping to lift
depression. It brakes the production of stress hormones such as cortisol
and adrenaline. Reducing these two hormones not only reduces feelings of
panic and stress, it also reduces the knock-on effect, production of
insulin and all the damage that follows.
carried to an extreme, endurance runners reach a ‘high’ where their
bodies are producing morphine-like substances, giving them a tremendous
feeling of well-being.
just like for eating, it is possible to identify the most favourable
pattern of exercise for human beings.
read the foregoing you will not be surprised to hear what the ideal
level of physical activity is:
children and old men - walk five miles per day, every day.
bodied men - walk and run 9 to 12 miles per day every day.
the studies confirm that these exercise patterns are the optimum for
good health. Indeed anyone doing that today is considered to have a high
level of fitness. For our ancestors, it was just the norm for everyone.
what are we to do in the modern world? For most of us it is just not
practicable to spend four hours a day exercising. Is it really necessary
to exercise so much? Are other forms of exercise more helpful?
hard answer is that you get out what you put in. The good news is that
the response is not linear. At the start you get a lot of benefit from a
relatively small increase in exercise. As you increase the level, the
benefits improve too, but not in proportion. It is the law of
is even possible to exercise too much. World class endurance athletes
are more prone to infectious diseases. In addition, they distort their
dietary habits for maximum performance - to the detriment of their
what is a reasonable compromise between what is desirable and what is
can put together the foregoing paleo-anthropological argument with the
studies and recommendations made by various authorities.
recommended physical activity is :
to 5 days per week of aerobic exercise at moderate to moderately high
to 60 minutes each session.
is the laconic specification. Let us look at what that means in
intensity aerobic exercise’ is one that raises your heart rate to 40%
of its maximum. Women, children and older men should aim to do this.
of moderate physical activity include
cycling, playing basketball or volleyball, swimming, water aerobics,
dancing fast, pushing a stroller, raking leaves, shovelling snow,
washing or waxing a car, washing windows or floors, gardening, golf and
to high intensity aerobic exercise’ is one that raises your heart rate
to 85% of its maximum. Able-bodied males should aim to do this.
of moderate to high intensity physical activity include
squash, hard swimming, vigorous cycling, manual labouring and weight
forget that the above are minimums! Nothing to stop a women playing
squash if she wants, or indeed a centenarian jogging 10 miles if he is
today’s modern America, the problem is the opposite. Many children and
young adults get out of breath just changing the channels on the remote
word of warning. Anyone who has a history of smoking, is or has been
severely overweight, is middle-aged or more, is under constant stress,
has a family history of heart disease – should get a check up for
potential problems. Advanced heart disease can have no symptoms. Even
regular exercisers who fit into the above categories can be struck down
Fixx, who wrote The Complete Book
Of Running and thereby set off the jogging craze, was such a case.
He had been a heavy smoker and had been very overweight He had a poor
family history, his father dying of a heart attack at the age of 43.
Fixx quit smoking, lost 50 pounds of surplus weight and started running
60 to 70 miles a week. Everything was all right for 15 years. Then at
the age of 52 he suffered a massive heart attack while running and died.
His coronary arteries were hopelessly blocked. They were almost
certainly far gone when he started his fitness regimen, but he didn’t
know - he had never had a check-up. And just being physically fit,
contrary to what he thought, was not enough to stop his arteries getting
worse. Rather, physical fitness is just one of the elements necessary to
health and well being.
about other forms of exercise? Callisthenics, muscle building,
stretching and so on? Yes, they are all helpful. Indeed the
recommendation is that everyone should be using stretching exercises at
least three times a week. Elderly people are particularly recommended to
do muscle building exercises and joint suppleness training every day.
This will ensure that they arrest the loss of muscle mass and keep their
Exercising for Weight Loss
people exercise to lose weight. We can use a knowledge of our
biochemistry to make sure this happens in the most efficient way.
we exercise moderately (40% of max heart rate), then the source of
energy that the body mostly uses comes from the triglyceride fats that
are floating around in the blood stream. These are the fats that we want
to burn! The body has to replace them from stores in the fat tissues.
however, we step up the exercise rate, then the body starts to prefer
energy from carbohydrates stored in the liver, muscles and blood. The
body will replace these later from what we eat.
good news then, is that moderately intense exercise is better than high
intensity exercise for fat reduction. This effect is particularly marked
if no carbohydrates have been consumed before, during or after the
exercise. So, go for your brisk, early morning walk on an empty stomach.
Avoid all sugary drinks, and certainly don’t eat any bad
carbohydrates. If you must eat during this period, restrict it to the
‘good’ foods, some low glycemic fruit for example. You won’t feel
hungry. Less conventionally, don’t be inhibited by your cultural
conditioning: it is quite possible to have a shrimp and vegetable
stir-fry or a mixed salad for breakfast.
for Competitive Sports
in order to obtain maximum performance is the domain of specialised
sports nutrition. The only reason for broaching this topic here is to
make an important point: sports nutrition has, as its main objective,
the achievement of maximum performance.
one example: ‘carbohydrate loading’. This technique, to stoke up
energy reserves before a race, makes extensive use of high glycemic
index ‘bad carbohydrates’ that are consumed in a particular pattern
over an extended number of days. To obtain maximum performance the
technique is very good. But, this is exactly contrary to the principles
of eating for good health.
is a trade-off that is rarely explained to athletes: performance vs.
too, that the ‘savvy eating for weight loss’ procedure explained
earlier is the exact opposite to that prescribed for eating for endurance
performance. For performance, athletes are recommended to consume high
glycemic index foods (that is, bad
carbohydrates) before, during and after the competition!
is readily acknowledged by sports nutritionists that this causes
hyperinsulinemia - and they know it wreaks havoc on arteries and
scrambles hormonal responses. They know, too, that hyperinsulinemia
locks up fat and makes it unavailable for burning by the muscles. This
is a drawback. Nevertheless, the calculation they make is that this is
the lesser of two evils - the greater energy surge from the bad
carbohydrates outweighs the loss of energy generated from fat sources.
have here an example of how food is used as a drug. A
performance-enhancing drug for athletes. In various ways what and how
you eat is having a drug-like effect on thousands of important bodily
surprisingly, conventional wisdom is coming to the view that physical
exercise should be more than just an episode on various days of the
week. Physical exercise needs to be integrated into the everyday pattern
of all, try to develop hobbies, sports and interests that of themselves
give you the base-load of exercise that you need. If you play golf one
day a week, go dancing one day a week, do some gardening one day a week,
and go swimming one day a week, then you are well on the way to being
well exercised. By all means go to aerobics, play tennis, jog round the
take every opportunity to work out those muscles as you go about your
day. Why stress yourself to find a parking space right next to the
shopping mall entrance? That only helps to raise stress hormones with
all the damage that that does. Park at a comfortable distance away and
walk those extra 100 yards!
Walk up the stairs instead of taking the elevator. Carry the shopping
instead of pushing the trolley.
we are so spoilt for labor-saving devices that we have, perversely, to
seek out labor intensive activities or make them up for ourselves. Push
yourself constantly to stretch your body’s physical capacity. Never
take the easy way out when the opportunity is there to challenge your
 Gregg et al; Ann Intern Med 1998;129:81-88,133-134.
[Exercise linked to longevity]; JAMA 1998;279:440-444.