There are many myths behind how weight gain occurs.  The energy balance that is achieved when maintaining the  body has been often quoted as the first law of thermodynamics.  This is that energy in equals energy out.  But this may need to be refined as it needs to take into consideration metabolism.  Because a person that is overfeeding will not explode to 1000kg in body weight.  There is another mechanism in place.  It looks at the balance between the three macros and weight gain.


The Three Macros and Weight Gain


The three macros and weight gain that we will consider are carbs, protein and fat.  These consist of all the energy intake we have throughout the day.  We can add another source of energy and that is alchol.  Alcohol doesn’t add any nutrients to the body and can be considered empty calories.


Carbohydrate Balance


We have seen in a previous post (see post) that an increase in carbs does not lead to an increase in body fat.  Only under extreme circumstances (greater than 85% of daily intake) will the body turn carbs into fat.  It is not an efficient process and doesn’t occur very often.  Carbohydrates either get burnt up or stored as glycogen in the liver and muscles.  Daily intake of carbs makes up 50-100% of stored carbs.  Carbohydrate balance is tightly regulated and controlled.


Protein Balance


We have seen in a previous post (see post) that an increase in protein does not lead to an increase in body fat.  Like carbs protein storage is tightly regulated.  The daily intake of protein makes up only 1% of the total protein that is stored.  Eating more protein doesn’t mean that you will put more muscle on.  The only way to put more muscle on is through growth stimuli such as growth hormone or through strength training.


Alcohol Balance


Like your vino?  Well it just so happens that alcohol does not get stored as fat in the body.  It is burnt up just like carbs.  However, it promotes fat storage and inhibits the burning of fat in the body.  This means that when you’re out drinking, it’s not the alcohol that is making you put on weight,.  It comes from the fat from the fries, chicken wings, cheese or all the deliciously fatty foods that you eat when having your wine.


Fat Balance


Daily fat intake only makes up less than 1% of the amount of stored fat in the body.  However, the energy that comes from fat is 6 times that of carbs and protein.  If there is an energy imbalance, that is you eat to much food then it is fat that is stored.  Similarly, if their is a daily deficit of 200kj/day then this will come from the fat stores.

So how come we don’t just keep putting on weight if we over indulge every day?  Why are there no 1000kg people in the world?  That is because the fat in the body increases the amount of fat that is burnt.




There is tight regulation between the type of food that we eat and how much fat we will put on.  The body is very efficient at putting weight on and very ineffective at losing weight.  At least we can see that reducing (but not excluding) the amount of fat in the diet will lead to the body maintaining a healthy weight.  The three (or four including alcohol) macros and weight gain is only influenced by fat and the power that alchol exerts over the burning of fat.




J Galgani, E Ravussin, ‘Energy metabolism, fuel selection and body weight regulation’, Int J Obes (Lond). 2008 Dec; 32(Suppl 7): S109–S119



%d bloggers like this: