How many Calories do i need to eat if i want to lose/gain weight?

The first thing you need to know in your quest to lose/gain weight is your BMR– your energy expenditure at rest (the number of Calories you’d burn if you stayed in bed all day).Once you have this figure you can calculate how many calories your body requires to maintain its current weight using another formula. Then from these figures you can either create a deficit to lose weight or a surplus, to add weight.

You use energy no matter what you’re doing, even when sleeping, so using the following equations we can calculate you’re BMR. Theses equations are influenced by gender, age, body size and composition and genetics. Caffeine and spicy foods can also increase BMR. As each year passes by, it becomes harder to eat whatever you want and stay slim, this is because your BMR decreases as you age. Likewise, depriving yourself of food in hopes of losing weight also decreases your BMR, which foils your intentions.

 However, a regular routine of resistance training to increase the muscle percentage in your body alongside cardiovascular exercise , always having a good breakfast, eating 6 smaller meals a day and drinking 6 – 8 glasses of water per day  can increase your BMR, improving your health and fitness when your body’s ability to burn energy gradually slows down.


 BMR formula:. Use the calculations below to calculate BMR, where:

 Wt = weight in kg, Ht = height in cm, A = age in years.

men: calories/day = 66 +(13.7 x Wt) + (5 x Ht) – (6.8 x Age)
women: calories/day = 655 +(9.6 x Wt) + (1.8 x Ht) – (4.7 x Age)

for example: Male 37yrs, 84kg, 182cm

66 + (1151) + (910) – (252) = 1875 CAL 

Now we have your BMR, we need to multiply it by your activity level to get your total daily energy expenditure.

Here is a great link to an online bmr calculator

Total Daily Energy Expenditure

Total Daily Energy Expenditure is the total number that your body burns each day through activity. When you know how many you burn each day through physical activity, then you know the following:

  •  How many Cal you need each day to maintain your weight
  •  How many Cal you need each day to lose/gain weight

It is often calculated using the Harris Benedict Equation which multiplies your daily BMR by an activity factor which you choose accordingly (See below). The only factor omitted by the Harris Benedict Equation is lean body mass. Remember, leaner bodies need more Calories than less leaner ones. Therefore, this equation will be very accurate in all but the very muscular (will slightly under-estimate calorie needs) and the very fat (will over-estimate calorie needs)

Exercise Level


Cal  Calculation (Daily Needs)

Little to no exercise

BMR x 1.2

Light exercise

1-3 days per week

BMR x 1.375

Moderate exercise

3-5 days per week

BMR x 1.55

Heavy exercise

6-7 days per week

BMR x 1.725

Very heavy exercise

twice per day, extra heavy workouts

BMR x 1.9

Total Daily Energy Expenditure = BMR x Activity Factor

My example = 1182 Cal  x 1.55 =         2906

Now that I know my Total Daily Energy Expenditure I know that a daily intake of this amount will help maintain my current weight.

In order to lose weight I know that I need to intake less caloriesthan I burn. This is called a deficit. And in order to gain weight I need to intake more calories than I burn– That is called a surplus. Now ½  Kg of body weight is roughly equivalent to 3500 Calso therefore if I cut my daily intake of Cal by 500 I would expect to lose ½ kg per week. If I was looking to gain weight then I would look to a surplus of 500 Kj per day. This would see me gaining ½ kg per week. This amount is seen as a healthy target for weight loss/gain. Remember though, all calories arent created equal and it is alot better for you to be getting your calories from good nutritious foods such as the ones i listed in my previous blog  – HEALTHY SHOPPING LIST

There are some great online food calculators/ diarys such as Myfitnesspal and CalorieKing which will help you to track the amount of calories you are eating. Using the settings tab you can also customise your macronutrient values/(carbs, proteins and fats) to your desired percentage split. For example, i find a split of 40 protein/ 30 carbs and30 fats works best for me when it comes to getting maintaining lean mass but dropping bodyfat

Hope this helps guys!

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