How much should I eat?? Part 1 - calories and the bigger picture.

How much should I be eating? How many calories do I need a day? Is there a bottom line on an Excel spreadsheet? Should pineapple go on pizza?

Questions I get asked all the time. I’m going to explore the answers a little bit in this blog and give you the framework to figure out what you need from a calorific point of view.

This blog will be split into two parts, with this first part explaining how to calculate calorific requirements. The second part will be published soon after this one, and looks at how appropriately split those calories with regards to protein, carbohydrates and fats, to give you an even clearer picture of how to structure your diet.

Also, yes. Pineapple does go on pizza.

So….how many calories do you need a day? The first thing we need to do, is get our heads around a couple of different numbers;

  • BMR - this is your Basal Metabolic Rate, the number of calories you need on a daily basis to carry out all normal bodily functions (breathing, brain function, keep the heart pumping etc.) and maintain homeostasis.
  • TDEE – this is your Total Daily Energy Expenditure, which is your BMR multiplied by an activity factor. This will give you the number of calories you need to carry out the tasks in a standard day, whether that is walking, working, exercise or anything else that requires energy.

There are a lot of online calorie calculators with a variety of different equations. They will all give you a similar answer, but the formula I’m going to give you is the revised Harris-Benedict equation. I’ve found it to be the most accurate as well as the easiest to adjust for activity levels and goal amendments.

I will give you the equation and then I will give an example of how to use it.

Harris-Benedict BMR calculator


BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) - 161


BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5


We will use a customer of Next Level Nutrition’s as an example who we have been talking to, to help him figure out his TDEE. The customer is a 29 year old man who weighs 79kg and is 1.82m tall, so for him, this would look like…….

BMR = (10 x 79) + (6.25 x 182) – (5 x 29) + 5

BMR = 790 + 1137 – 145 + 5

BMR = 1787

That means, doing nothing all day other than his body performing it’s normal functions, this man would burn approximately 1787 calories per day.

That is a great starting point, the real trick is now figuring out how many calories you need to actually be active. To do this we need to multiply your BMR by an activity factor, based on your daily activity levels .

Activity level

Multiply BMR by

Sedentary job/little to no exercise


Lightly active job/exercise 1-3 times per week


Active job/exercise 3-5 times per week


Physical job/exercise most days


Physical job + intense exercise most days



This mean if the man we are using as an example has a lightly active job or exercised 3 times a week, we would multiply his BMR of 1787 x 1.375. this would give him a TDEE of 2457. These are known as ‘maintenance’ calories.

That means, on days when this person is as active as he normally is, he would burn roughly 2457 calories. Obviously if he were having an easy, relaxing day, he would burn less. If he had a very intense day, he would burn more.

If you’ve worked out your TDEE, you now know approximately how many calories your body will burn on an average day. So what next?? Well now we make any adjustments based on your goals.

  • If you wanted to maintain your current weight, you use the TDEE as it is.
  • If you wanted to lose weight, you would reduce your TDEE by 10%, a healthy aim is to lose 0.3 - 1kg per week depending on your starting point.
  • If you wanted to gain weight, you would increase your TDEE by 10%, a healthy aim is to gain 0.2 - 0.7kg per week depending on your starting point.

Now this bit is very important, so I’m putting it in bold….I’m not shouting.

Whatever calorie requirement you set yourself using any kind of formula is your starting point. Not your set in stone calorie intake for every day from here on out. You should use your calculated calories as your daily or weekly intake goal for a couple of weeks, and then you can assess how those calories have impacted your target.

If you were planning to lose or gain weight and you are happy with the progress you have made, then your calculated numbers are working for you. If you haven’t lost or gained any weight, adjust the numbers up or down in 10% increments accordingly and run with these adjusted numbers for a couple of weeks before assessing again.

Remember, this is a process, so will take time. To get where you want be whilst doing it in a healthy and sustainable way is the goal here.

Also remember (this blog isn’t disappearing so you don’t actually need to remember it….just read it again) that you may not change weight at all, but instead change body composition. You may find your clothes are fitting better than they were a couple of weeks ago and you feel better, but the scales haven’t budged. This means that the percentage of fat and muscle you are carrying has changed. You may even find yourself with a slight weight increase if you have incorporated a good resistance training programme alongside eating well and recovering properly. For this reason, don’t obsess over what your weight is. Yes, weight is an indicator of change, but also consider how you feel, how your clothes fit and how you look to gauge progress and then adjust accordingly.

You may find it easier to try to hit your calorie total on a weekly basis at least, this is because as I mentioned earlier; some days you will need less or more calories than others. This also allows flexibility for incorporating days when you might want to eat a bit more or an occasion you want to have some calories ‘banked’ without negatively impacting your long term progress. If we used our man in the above example, it might end up looking something like this;










Lightly active day

Intensely active day

Rest day

Lightly active day

Rest day

Intensely active day

Rest day


TDEE target









Actual calorie intake










You can see that adjusting calorie intake slightly for the day’s activity level allows flexibility to indulge a little on Saturday if wanted. The vast majority (at least 80%) of the calories consumed should be made up of nutrient dense, healthy choices. The remainder of the calories (at most 20%) is where you can allow yourself a small treat to help with sticking to your new goals and minimise the risk of giving up on the plan due to your diet being overly restrictive.

You will also notice the actual calories consumed is nearly 300 less than the weekly target, that only works out to be just over 40 calories a day, which is borderline insignificant.

For those wondering….yes, you can go about your normal day on only your BMR calories. This is because any energy you need that you don’t get from food, can be taken from your energy stores (muscle glycogen and fat). Don’t do this too often though as it will affect performance in exercise and is not optimal for a healthy lifestyle.

Always remember; the numbers and percentages above are just guides, a framework for you to work from. Once you have a starting point, you can assess and adjust as you go.

You are now armed with the tools you need to figure out how many calories to use as a starting point in reaching your next goal!

How and when those calories are portioned is the next piece of the puzzle. So in the next blog, I am going to explore; nutritional loading and calorie intake timing as well as macro splits.