I was casually walking down Blackheath high street this morning in nothing but a pair of flipflops thinking about the rugby (swing low sweet chariot…) and people were staring in wonderment and kept asking “How many calories should I be eating to look like that?”  So I thought I best share the knowledge….

To lose weight you need to be in a calorie deficit (i.e. you expend more energy than you eat on a daily basis). As a general rule of thumb for sustainable weight loss you want to be in a deficit of around 500kcal/day. This is enough to see decent progress each week, but without getting starving hungry from not eating anything and importantly not wasting away important muscle mass which will likely occur with an extreme calorie deficit.

But Joe how do I figure out how many calories I’m burning each day? This is probably one of the most frequent questions I get asked, and the answer is simply that it is different for every single individual depending on a number of factors, but most importantly your height, weight, age and your physical activity levels.

Without further ado whip out your scientific calculator (or Google “scientific calculator”) and use these formulas:

Step 1 – Calculating your Basal Metabolic Rate

Your basal metabolic rate (BMR) simply means the amount of energy used by your body during a 24-hour period if no activity is performed. In other words, if you’re inactive for 24-hours straight, you’d still “burn” the amount of calories equivalent to your BMR.

For Men

BMR = 66 + (13.7 x weight in kg) + (5 x height in cm) – (6.8 x age)

For Women

BMR = 655 + (9.6 x weight in kg) + (1.7 x height in cm) – (4.7 x age)

Step 2 – Factoring in your activity level

The more active you are the more you’ll burn fuel. To get an adequate estimation you need to multiply your BMR by an activity level

Activity level factor Activity level




Very light activity


Light activity*


Moderate activity


High activity


Extreme activity
  • By sedentary we mean doing nothing all day (sleeping and watching TV).
  • By very light activity we mean doing nothing physical. Working a desk job or on a computer and not performing any type of physical activity during your day.
  • By light activity we mean having a non-physical job (desk, computer, etc.) but performing some sort of physical activity during the day (e.g. above average walking) but no hard training.
  • By moderate activity we mean having a non-physical job, performing some sort of physical activity during the day, and including a daily workout session in your routine. This is where most of you are at.
  • By high activity we mean either training plus a physical job or non-physical job and twice-a-day training sessions.
  • By extreme activity we mean a very physical job and daily hard training.

* As a gauge most of my clients who have a sedentary job but train with me twice per week I give as 1.3 activity factor.

Your Daily Expenditure Is:

BMR x Activity Factor

Step 3 – Adjusting your Calorie Intake too your goal

For those of you looking for good sustainable fat loss, simply -500kcal from your energy expenditure. Looking to maintain you weight (remember maintaining your weight doesn’t mean you won’t be changing the way you look if your training is correct) leave the number the same. Looking to gain lean muscle mass then add 500 kcal. This is all assuming your doing your work in the gym!

To count your calories I would highly recommend the website/mobile app called MyFitnessPal.

Your friendly Blackheath Personal Trainer,

Joe Birch BSc MSc Pn-1 esq

Personal Trainer Blackheath