Lots of my posts recently have highlighted that many people will restrict calories to try and achieve weight loss. But how do you know how many calories you need each day? and therefore, how can you ensure you are in a calorie deficit?
What are calories?
A calorie is a unit of energy. We use it is a measurement of the amount of energy within an item of food and drink
How can you calculate your daily calorie needs?
If you have ever looked into this you will find that there are loads of different calculators online and various websites showing you different ways to do this. So here are 7 that I have found…
W = weight in kg, H = height in cm, A = age in years
I weigh 82kg, am 180cm tall, and 32 years old, therefore…
66.47+1127.5+900-216 = 1878
However, this doesn’t account for body composition (% of my mass that is fat and muscle) or activity level. Most websites tend to agree on this next part. How to incorporate activity level into daily calorie requirements:
- BMR x 1.2 for low intensity activities and leisure activities (primarily sedentary)
- BMR x 1.375 for light exercise (leisurely walking for 30-50 minutes 3-4 days/week, golfing, house chores)
- BMR x 1.55 for moderate exercise 3-5 days per week (60-70% MHR for 30-60 minutes/session)
- BMR x 1.725 for active individuals (exercising 6-7 days/week at moderate to high intensity (70-85% MHR) for 45-60 minutes/session)
- BMR x 1.9 for the extremely active individuals (engaged in heavy/intense exercise like heavy manual labor, heavy lifting, endurance athletes, and competitive team sports athletes 6-7 days/week for 90 + minutes/session)
So you can use these generally accepted figures to work out approximate daily caloric needs. I would probably fall in the moderate exercise category. Therefore…
1878*1.55 = 2919 = my daily calorie requirement
11 calories per lb BW
I weigh 185lbs * 11 = 2035
2035*1.55 (activity level) = 3154
This is probably the easiest calculation to use, but also one of the most approximate.
The Sterling Pasmore equation
BMR= Lean body mass (lbs) x 13.8 calories
You can obtain your lean body mass from body fat measurements:
Calculate lean muscle mass vs. fat mass:
Body fat % x scale weight= fat mass
Scale weight – fat mass= lean body mass
My weight = 180lbs, fat% = 12%
Therefore, Fat mass = 21.6lbs
180-21.6 = 158.4lbs lean mass
BMR = 13.8 * 158.4 = 2186
BMR * 1.55 = 3388 calories
Body weight in lbs * 14 or * 17
180*14 = 2520 and 180*17 = 3060
Similar to method two this is very approximate. It also gives two different figures, and therefore a range, so it is hard to determine which is most appropriate.
This calculator doesn’t account for lean mass and therefore I am assuming it uses the average body fat % (which I am below), which is why my calorie needs are lower than other calculations.
370 + (21.6*lean mass in kg)
82kg * .12 = 9.8kg fat mass
72.2kg = lean mass
1930*activity level (1.55) = 2992
Try them out for yourself. Which one do you find easiest to use? Do you know of any better methods that I may have missed?
All the varying calculations above show just how difficult it is to accurately calculate daily caloric needs. My daily calorie requirements range from 2520-3388 calories per day depending on which method I use. However, using the average (2936) it is would be safe to assume my daily calorie requirements are around 3000 calories.
Now we have calculated our approximate daily calorie needs. How much of a deficit do we need or should we be in?
Many websites will suggest that you should restrict calories by 500 calories a day. This is based on the assumption that a weekly reduction of 3500 calories (500 calories a day for 7 days) will result in a lb of fat loss every week (9 calories in each gram of fat). However, this theory is very flawed and not accurate, as highlighted by research. I also shared a great video in ‘Remember, Abs are made in the Kitchen‘ that highlights why this is not correct and why it is not that simple.
It is now thought that calorie reduction as a % is far more appropriate as it accounts for individuals daily energy expenditure. Suggestions vary from 15-25%. If I used a 20% calorie deficit for example, my daily calorie intake for fat loss would be 2400 calories.
It can be found and is suggested that calorie reduction may result in muscle loss. As muscle weighs more than fat this can contribute to larger losses in weight. However, this is something that we want to avoid.
Personally, I have never really counted calories or macros because, lets be honest, it’s no fun. However, I know that when I have lived in a calorie deficit (like when I tried the keto diet) I did shed excess fat. See my picture above, which highlights my body composition after 6 weeks on the keto diet where I struggled to eat enough fat to meet my caloric needs. I really found the best results when I completely removed sugar from my diet (including alcohol) and exercised regularly (4-6 x a week). However, I struggled to maintain this as I felt tired a lot and came to the conclusion that I was not going to live this way.
What we now know and can further learn from this
- You need a maths degree to work daily calories needs. If you are going to use any of the methods I have suggested then 1) get a calculator and 2) I would suggest method 1 or 6 as they were the closest to my average. However, bear in mind it is impossible for us to work out the precise figure. Let me know which method works best for you.
- Look at the calculations… age slows down BMR and lean muscle mass increases BMR. Therefore don’t get older and get building some muscle
- A calorie deficit can possibly result in muscle loss. Therefore make sure you maintain your training and eat at least 0.8g of protein per lb of body weight to provide your body with sufficient protein to avoid this. This would be 144g of protein a day for me (I weight 180lbs). Some research suggests exceeding this 0.8g per lb of body weight, especially when in a calorie deficit AND whilst training.
- Losses in weight and reduced calorie intake = reduced BMR (metabolism) – therefore you need to keep re-calculating your daily calorie requirements as you lose weight or do something else (read Cheat Meals).
- Reduce your calories as a %. I would suggest starting with 10% and maintain this for a period of time before considering increasing your deficit.
- Counting calories, doing all of this, is not fun – so are you sure you want to do this? Surely eating and food is supposed to be enjoyable? Follow my tips in Calories versus Carbs: fat loss PART 2
- If you really want to track your calories and try ensure you are in a calorie deficit I recommend using the myfitnesspal app – this way you don’t have to add up the calories yourself as the day goes on.