TDEE - 20% or Calorie-based deficit?

duckiec

Knowing that all the calculators, tools, etc, are all estimates at best, the process is not linear or exact... which method is preferred, in terms of overall health, success, and goal of losing fat, keeping lean mass? TDEE - 20%, or TDEE - 500-1000 calories a day?

For example, I use a Fitbit to calculate TDEE (yes, I know, estimate). My average TDEE = 2200/day. It was actually a little higher, but I had some extra long workouts I won't be doing every week. 5ft 37yo female with about 30lbs left to lose.

TDEE - 20% = 1760, for a deficit of 440 cal/day. That's only a little under a deficit of 500/cal a day, probably statistically the same.

But I've been agressive, and been shooting for closer to -1000/cal day. This is easier, too, when my Fitbit puts my TDEE around 2500-2800 on busy days (never thought little ole me was so active!).

TDEE - 20% would be slower, I suspect, but is there any strong argument (besides getting to eat more food) to go with that vs. the 500-1000 calorie/day deficit?

FWIW, since i've been tracking with for about 3 wks with my Fitbit, maintaining the average 1000ish cal a day deficit, I HAVE NOT lost an average of 2lbs/week. Not a plateau yet, but it's not coming off as "according to the numbers." Perhaps having too many days with over 1000/cal deficit is contributing, as I've heard that over 1000 cal/day deficit is a key component in slowing one's metabolism.

Just curious if there's any research, opinions, etc, that make either strategy come out over the other. Thanks!

jody664

Bump.

I'm interested too. Ironically I *just* now calculated my TDEE (based on FitBit's estimate) and it was almost identical to yours! My average burn per day is 2126/day. I'm finding it confusing. I don't know if I should trust MFP's calories left for the day or FitBit's.

deksgrl

Because a straight -500 or -1,000 calories may put you below your Basal Metabolic Rate. Your goal should be to lose fat reasonably without creating too much of a deficit so as to preserve lean body mass.

The appropriate % cut from TDEE should vary depending on how much weight you have to lose. Very obese people may be able to go as much as a 30% cut. Someone with 10-15 pounds to lose should be at a 10% cut.

The other benefit is that your exercise calories are included in TDEE and so you don't have to track (and trust) MFP estimated calorie burns. Keep in mind that MFP does not calculate your TDEE with exercise included, it only estimates what your calorie needs are for existing and normal daily activities, not working out. MFP's estimated calorie needs are going to be lower than what you will get with other TDEE calculators, so you already have a deeper deficit to start with, then subtracting a flat amount of calories can be too deep a cut and you sacrifice LBM.

duckiec

Interesting points, thank you!

To clarify - I've got an HRM so I'm not using MFP to calculate my exercise burns (I know, another estimation tool- nothing is exact), and my TDEE is coming from my Fitbit, so the 500-1000 deficit a day is based on those reports, not overall MFP's estimate.

I did not, however, consider my BMR at around 1400. Lean mass is at risk when you drop below that, right? Not necessarily at -1000 cal/day, but just that -1000 cal/day risks going below BMR. Fitbit guidance/reports are definitely lacking in that area- they don't give you a minimum.

I guess so long as I'm between -1000 /day (but over BMI) and TDEE-20%, I'll be at a deficit and should be losing... now if the scale would only cooperate!

deksgrl

-1,000 is too deep a cut. Your -20% should be plenty sufficient to produce results. If your TDEE is around 2200, then a 1,000 calorie deficit would be like a 46% cut. Really unsafe for anyone, even if you were truly obese, which you are not. This is probably why your scale is not moving, you are producing too much stress which releases cortisol, which prevents weight loss as a survival mechanism.