Updated: Apr 25
Calories is probably one of the most demonised words in health and fitness. The thoughts that calories are bad, low calorie foods are good for you and that eating more than 2000 calories a day will make everyone fat are common place.
Calories (and for the most part nutrition) are actually super simple and nothing to be afraid of. Although the behaviour patterns of calorie consumption may be hard to fathom the actual math behind them is pretty easy.
If you want to gain weight you need to be in a calorie surplus. If you want to lose weight you need to be in a calorie deficit. But when are we in surplus and when are we in a deficit?
This will be individual to everyone and will be impacted by your weight and activity levels more than anything. We can get a pretty good idea of how many calories we need using the following formula:
Basal Metabolic Rate x Activity Level
Our Basal Metabolic Rate (BMR) is the amount of calories we need to basically exist. The minimum number we need to sit still and have our organs function, it does not support any activity. We find our BMR by multiplying our body weight in KG by 24 if you are a male and 22 if you are female.
Eg. A 85kg male would be: 85 x 24 = 2,040.
This 2,040 is the number of calories this person would need to just be. We can then multiple this by their activity level for which we use a rating between 1.1 - 1.7. The lower number being for inactive and the higher for the most active. If we assume this person is relatively active: has a somewhat physical job and exercises four times a week we might use 1.5 as their activity level number. Our equation then becomes:
2,040 (BMR) x 1.5 (activity level) = 3,060
This 3,060 is the number of calories this person would need to consume to maintain their current body mass. In order to increase their mass they would need to add a surplus and to decrease their mass (lose weight) they would need to add a deficit. You can create a surplus or deficit in two ways: add or subtract activity or add or subtract calories.
If you move more your activity level would change in the equation and your calorie requirements would increase and vice versa for less activity and decrease.
The most common approach though is to change our calorie intake. If we create a calorie deficit of around 500 calories a day we would expect to see body weight decrease by around 0.5kg (1lb) over a 7 day period. Now depending on how high your maintenance calorie number is would dictate how I think you should pick a deficit.
Someone whose maintenance number of calories is 3000 would be cutting around 16% of their calories if they had a 500 cal deficit. Someone else with a maintenance number of 2200 creating a 500 calorie deficit would be losing around 23% of their overall calorie intake. This is a huge difference in food quantity and energy intake and would need to be adjusted. As a good base creating a 10% deficit is a good start. As with everything in health and fitness it can be adjusted according to the results seen or desired.
The reverse can be applied for gaining weight. A 500 calorie surplus would roughly equate to 0.5kg of weight gain over a 7 day period.
And it really is that simple. If you are losing weight you are in a calorie deficit. If you are gaining weight you are in a surplus. If you are consistently the same you are eating the right amount of calories to do so.