Why “Calories In” Don’t Always Equal “Calories Out”…

By Tim Bean

For years we’ve been told that if we eat the same number of calories as we burn, our weight will stay the same.  We will neither lose weight, nor gain it. This presumption is, however, false, and very likely one of the reasons people who follow this flawed logic struggle with their weight to this day.  Like me many years ago, you may be one of them…

It’s been calculated (reasonably accurately) that the average man at rest might burn around 2400 calories a day in metabolic, or thermal, activity, although this will vary widely from individual to individual.

A calorie (or more correctly, a kilo-calorie) is a unit of heat energy, and our bodies produce lots of heat through the many metabolic functions that go on all the time in the body.  This heat is either retained, radiated, convected or conducted away from our bodies.

It is known that you cannot create or destroy energy – it exists. This is physics, and it is said then that if you eat 2400 calories and you burn 2400 calories, you have neither a surplus nor a deficit for your metabolic requirements, and so you will neither lose, nor gain, weight.

So far, so good.

EXCEPT the calorie figures assigned to the various foods we eat have been obtained by incinerating different foods in a Bomb Calorimeter in a lab, where the food is totally consumed leaving nothing but ash.

Unfortunately (or fortunately, for we would otherwise die quite quickly) our bodies do not operate like that, so this calculation is, in fact, quite irrelevant.

You see, not everything we eat is burned up as fuel. 

Foods contain proteins, fats, minerals and so forth, that are broken down and utilised in cellular replacement and repair. Fats coat themselves with proteins (lipo-proteins) to carry cholesterol – the material your brain is largely made up of, and from which most of your hormones are manufactured.

Other proteins repair and restore muscle tissue, bone tissue, cell wall structures and support other organs in your body.

Some of the calories we eat never even make it to the bloodstream – we pass about 600-800 calories a day in excrement (dead bacteria, cellulose, etc), depending entirely on where those calories came from in the first place, and how efficient our digestive systems are.

So here’s the bottom line:  Controlling weight gain or loss by balancing the listed calories from food and drink we take in against the calories we burn, whilst correct in a laboratory setting, in a living bio-organism such as ours is a nonsense.

It is a law of physiques, yes, but it doesn’t apply completely here – the calculative assumption is wrong.  And besides there are just far too many other variables.

Our best bet is to concentrate on the quality of a nutritionally-dense intake, and control our weight, if necessary, through manipulation of that against the exercise we take.