The 500 Calorie Deficit Myth
If you’ve been around the world of macro-tracking for a while, you may have heard of the “500 calorie deficit per day” rule.
The idea is:
Body fat = stored energy
We measure energy from food using calories (kcal)
1 lb of body fat is equivalent to ~3500 calories worth of energy
Therefore, in order to lose 1 lb of body fat each week we need to be in a ~3500 calorie deficit across the week, or 500 per day (3500/7).
Simple, right? Not quite.
1 lb of body fat means different things to different people.
To a 100 lb 5’0 female that’s 1% of her total bodyweight.
To a 300 lb 6’2 male that’s only 0.33%.
Should they really be dieting using the same deficit amount?
We don’t think so. Your rate of loss should be individual to you - accounting for your own individual circumstances, lifestyle and goals.
You’re better off aiming to lose a percentage of your bodyweight per week, rather than an arbitrary 1 lb.
So, what’s the right percentage?
You should aim to lose somewhere between 0.5% - 1% of your total bodyweight each week on average. Remember that is an average - the scale won’t drop linearly each week.
AIm closer to 0.5% per week if:
- This is your first time dieting;
- You’re already quite lean;
- You strongly value keeping hold of your hard-earned muscle mass.
Aim closer to 1% per week if:
- You’ve done this before;
- You prefer to suffer a little more to get the weight off quicker, to start your muscle gain phase earlier;
- You've got a decent amount of weight to lose;
- You need to get extremely lean aka bodybuilding competition, photo shoot.
Going faster than 1% could risk muscle loss, rebounding and a potentially chronically suppressed metabolism.
That’s what may have happened when Biggest Loser contestants were found in this study to have gained back most of the weight they had lost during the show.
As expected, the contestants experienced a suppressed metabolism after their weight loss (that’s normal). We would expect, however, a suppressed metabolism would up-regulate in response to gaining weight back. Unfortunately in their case, gaining the weight back did not restore their metabolism to pre-show levels!
On a side note, Dr Kevin Hall’s follow-up study pointed out that the contestants who performed the most activity even after the show, saw the greatest down-regulation in their metabolism.
Yet another nail in the coffin for those who prioritise cardio over nutrition for weight loss ⚰️
So how do you figure out how many calories you need to eat to lose bodyweight at the optimal rate?
Technically, you could track everything you eat for ~4 weeks and track your bodyweight too. Then use that data to figure out whether you’ve been in a surplus or deficit over that time (and by how much). From there you can calculate your predicted maintenance, then use another series of equations to figure out your optimal deficit to lose weight at the desired rate.