Don’t believe your calorie calculator

If your goal is to lose some weight and body fat, then chances are you’ve checked out one or more of the many calorie calculators available. Apart from the minor differences in the results each one gives, you may have found that your progress is minimal at best. Or you may have found that after working out the calories from one of these calculators, that your ability to stick to the insanely low numbers is more difficult than it should be and you fall off track easily.

Then possibly you have come to the erroneous conclusion that you just can’t do it and it’s not worth the effort.

But what if the calculators are at fault?

Where the problem(s) lie

1- Each calorie calculator works out your baseline calories from placing a line of best fit into the data collected from a number of participants whose weight and basal metabolic rate is known, much like in the table above. The more participants, the better the line of fit is. However, regardless of the accuracy of the line, there will always be more people above and below the line than actually on it. In fact, there are probably less than 5% of the points on the line, and that would be in a massive data set.

In other words, the result you get from a calculator is likely a very rough approximation of your daily calorie needs and that’s before we get on to the activity multipliers.

2. The calculators work out your calorie needs based on you doing nothing each day apart from being alive. Imagine being in bed all day, not moving at all, and that is what is worked out. Each calculator then uses an activity multiplier to add in daily movement, exercise and the energy demands of consuming and digesting the food you eat, to give you the calories per day you need.

Each multiplier (usually in the range of 1.1 – 2) is based on certain assumption and farily broad categories. This often puts your calorie target at the top end of what you may need. And if you are below the line of best fit, then your chances of hitting a deficit are minimal.

Secondly, we tend to overestimate our activity levels (along with underestimating our calorie intakes when we eyeball it). So if you are seated for 40+ hours a week, and train 2-3 times, and spend the rest most sedentary, then be honest and err on the side of caution.

3. Our days can often vary significantly enough to make it so that instead of a single calorie target you actually have a range of numbers depending on training, work and home activities. So you may be way under calories one day, but way over on the next.

What to do instead

You are unique, and as so your calorie expenditure and needs is also unique. So no calorie calculator can replicate the daily fluctuations of your life and lifestyle. So it’s time to become your own experiment.

Becoming your own calorie calculator

Step 1. Track everything every day for 2 weeks. And I mean everything, including your weight. Be honest and be accurate. Weigh your food, measure amounts and log accurately. If you are using myfitnesspal, then make sure the entries you use are accurate for calories and macros. Where you can, scan the barcodes on the food you have in order to get the official numbers. The key here is your accuracy over the 2 weeks. Yes it’s boring, but it needs doing.

Step 2. Work out your average calories over the 2 weeks. Assuming your weight stayed within 2-3kgs of your starting point, then this number is your maintenance number. In other words, if you kept eating this number of calories each day, you’d stay exactly as you are. Assuming, of course, your lifestyle and activities stayed the same.

Step 3 (optional, but recommended). Look for trends. Did you find that on certain days you ate more than others? Was it the weekend? Training days? You’ll use these days to manipulate your calories around your lifestyle and help make it a more sustainable process.

For example, if you always go high at the weekends, then you obviously value the freedom and social eating opportunities the weekend provides. Therefore if you try to limit these too much then you will likely fall off track. Similarly, if you eat more on training days, you may want to increase calories here and reduce them slightly on non-training days.

Like this:

how to adjust your calories based on daily needs

Step 4. Set your deficit at between 15 and 25% depending on your starting point and ability to stick to the lower calories. If you have a lot of weight to lose, then you will probably find a 25% reduction relatively easy to handle, resulting in a quicker initial drop in weight and more motivation to keep going.

Step 5. Adjust your calories over the week as per the pic above, making sure your average for the week is in line with your deficit. Then work to hit the target each day. Don’t stress if you go a little over on any given day, just aim to get as close to the target each day without it becoming a fixation and taking over your life. Remember that the target is really a range, and your results will come from what you do most often. If you fall off track you’re only ever a meal away from getting back on track.

Finally, remember that you will likely need to adjust a little as you go. This is a part of the process and completely expected. It’s rare that someone nails this at the first attempt. So give yourself a break, learn from any missteps and keep going.

If you would like some help with this, consider my online coaching program


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