The other day I heard an
interesting interview with Dr Lee Goldman on the radio. In it, he discussed how
evolution has done the dirty on us. For thousands of years those who ate all they
could and stored the excess as fat were more likely to survive, breed, and have
living children. As a result, humans have a tendency to eat more than they need
and store fat. Now, with abundant food for many, we are suffering the effects
of obesity, diabetes, heart attacks etc. And because the effects occur after
most people have already had children, there is no evolutionary pressure to
reverse the trend.
Then when asked why some people can eat as much as
they like and not put on weight, he said something
foolish:
"Calories in and Calories out.
Number of Calories you eat, if that exceeds the number of Calories you burn, in
terms of your exercise, you'll gain weight."
There are a number of
problems with this statement which made me wonder whether his main hypothesis
was flawed (must follow up sources at some stage).
What is a
"Calorie"?
A "Calorie" (big C)
is actually a kilocalorie, that is, 1000 calories (small c). That is, roughly,
the amount of energy needed to raise 1 litre of water 1°C. (I still remember measuring this for sugar in 5th
form chemistry and being rapt that my result was within experimental error of the
official value.)
It comes from the Age of Steam
when the calorific value of various fuels was important to know. But biology is
more complicated than chemistry. The first hurdle is, not everything in food
with calories is digestible by humans. So about 1990, for food labelling, the simple
bomb calorimeter method was replaced by the Atwater
system which sums the energy of the nutrients such as protein, carbohydrates,
fats etc.
Calories In
The Atwater system is an
approximation. It does not take into account the interaction between
nutrients that will affect the energy available and is out for some diets –
such as a low-fat high-fibre one.
Then let's look at
"indigestible fibre". Some people have the gut microbes that allow
them to digest it to some degree - not as much as a cow but maybe as much as 1.5
calories per gram of fibre. But it varies. People's gut flora are as
individual as a fingerprint.
In fact, some people's microbiomes
are more efficient all round. For a given amount of food some people get more
out of it. If one person with the better harvesting microbiota and another with
the inefficient type eat the same amount of food – and they are alike in every
other way – then the
person with the better microbiota is going to put on more weight.
Which bring me to the next
point. People are not made the same. One obvious difference is their sex.
Another is their soma type which is a reflection of their genetics. For
instance, in theory the best body type for a dancer is an endomorph
as they have flexibility and strength – however they also have extremely
efficient digestive systems which means they tend to put on more weight than is
commercially acceptable in an entertainer.
And added to this are a range
of diseases that affect how well food is metabolized – diabetes, Crohn's disease,
food poisoning for example. And other factors such as a lack of a gallbladder, hormone
levels, and various medications.
Finally, people's ability to
absorb food changes with time, environment, stress, age, etc.
So, the Calorie information
on the packet may be wrong in terms of how it is metabolized by the human body.
It may be wrong because of the type of gut microbes you have, genetic inheritance,
epigenetics, your sex, disease, medication, stress – to mention a few factors.
Calories Out
Again people use energy at
different rates – even when doing exactly the same thing in the same
environment.
Calories are used just to
stay alive. They are burnt in sleep as well as work, sitting, lying, or
running. Each person has their own mix of activities – and their own efficiency
in doing them ("more efficient" means you use less energy so are more
likely to put on weight).
And obviously more energy is
expended when the body is cold to maintain core temperature. What might
surprise you is that in extreme cold this can be 180%. So you can
eat almost twice as much as in a normal temperature environment.
Exercise has some effect on
the calories burnt but not as much as you might think. Doing nothing the
brain uses 20% of the body's energy.
And although cardiovascular
exercise uses calories, dance involves "exercising smarter". What is
seen as "grace" is the result of training your body to generate
movement with the least amount of muscle. If you do the same number of hours
practice, as you improve you will "exercise" less. Which is a good
reason to up your practice hours, add some folk, or cross train with something
more cardio vascular.
Summary
Unfortunately it isn't as
simple as "calories in, calories out". How the in‑calories are
digested is individual to each person and their current environment and health.
And although exercise will have an effect on how many calories you use – it may
not be as many as you might think.
But the last word from Dr Goldman
was no matter how hard it is to not put on weight, taking it off is much harder
as you struggle against millennia of evolution.
