A word on calories

You might be surprised to know that a calorie isn’t a tangible ‘thing’, it is instead a unit of measurement. Although the term calorie is used most often in the lexicon of food and nutrition, it could be applied to many other things; the amount of energy required to heat water, for example, or as a unit of heat itself equal to 4.1840 joules. It can in fact be used to describe anything that carries energy – in case you ever wondered, one ton of coal contains the equivalent in energy of 7,004,684,512 calories. This is the best place to start when considering calories as it removesย  notions of calories being in any way related to what we eat (for more information see).

So, a calorie is unit of energy, and our bodies need this caloric energy in order to function. But understanding how the body uses those calories is another matter. The best place to start here is to look at the body’s primary source of energy, glycogen. Glycogen is the storage form of glucose and is what every single cell in our body requires in order to work. As a macro-molecule, glycogen is not as as energy-rich as fatty acids, meaning they hold less calories.

  • 1g carbohydrate = 4 calories
  • 1g protein = 4 calories
  • 1g fat = 9 calories

“Sounds great, I’ll just go it a cheese toastie then as that’ll give me lots of energy!” Not so fast. When drawing upon energy for sudden bursts of strenuous movement it is glycogen that your body turns to as it is readily available and metabolised by your body very efficiently. And lo-and-behold the best sources of glycogen are fruits and vegetables and starches like rice, potato, and gluten-free pasta.


The biggest myth in the business is that carbs make you fat. Of course the supermarket and fast-food corporations would like you to think that, how else would everyone queue up like good little citizens to pour money into their coffers? Sure the body can chose to store glycogen as fat, but it won’t because it is an incredibly inefficient process using nearly twice as many calories to do so. Fat, on the other hand, has no problem getting itself in there. If you have 100 extra calories in fat (about 11 grams) floating in your bloodstream, fat cells can store it using only 2.5 calories of energy; if you have 100 extra calories in glucose (about 25 grams) floating in your bloodstream, it takes 23 calories of energy to convert the glucose into fat and then store it. Given a choice, a fat cell will grab the fat rather than the carbohydrates because fat is so much easier to store.

It is true that your body has a limit of how much glycogen it can store, around 2,000 calories worth, with any extra being stored in the body’s fat cells. Which in broscience means “carbs make you fat”. However, if you are exercising regularly and eating carbs regularly this will not happen as your body is constantly needing the glycogen for fuel. But people hear the line “excess glycogen is stored as fat” and simply use that as an excuse to eat meat and cheese without taking responsibility. Fill those glycogen tanks and get the hell outside! And you don’t just need carbs to exercise; glycogen is the only source of energy for the brain and the central nervous system, which is why when you’re hungry and undercarbed you are irritable and weak. So when you’re teacher at school tells you that oily fish is healthy ‘brain food’ feel free to educate them.


Those who take part in the high-fat, low-carb ketogenic diet – whereby you force your body to rely on fat as its energy source – sing it’s praises for fat loss, which is fine, but it isn’t natural as every scrap of science says that glycogen is your body’s energy source. If you return to my previous post about carb restriction you will see that cutting your carbs can lead to dehydration as, for every gram of carbohydrate consumed, the body needs three grams of water to store it. Lose the carbs, you lose the water, resulting in unhealthy weight loss. You can also say goodbye to strenuous exercise or simply anything that is going to result in the formation of lean muscle mass.

On a high-carb, low-fat diet you’ll have so much energy that not exercising – or not just getting out and being productive – won’t be an option as you’ll have too much energy not too! You’ll be thinking clearer, moving faster, and getting healthier. What could be better than that?



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