What is an unsafe weight loss rate and why?

dolorsit

I keep reading that you should keep weight loss to under about 1%/week. Since Jan 1, I've been losing a bit over that at about 1.2% per week, half of which is a food calorie deficit and the other half is additional exercise (running and cycling). What might be the complications of losing weight too quickly, other than just putting it all back on again later at some point?

Thanks!

L1zardQueen

Maybe getting too hungry between meals. Muscle loss. Hair loss.

Lietchi

Potential complications: loss of muscle mass (the heart is a muscle too!), hair loss, brittle nails, fatigue...

wunderkindking

Weight loss too fast is also a great way to kill your gallbladder apparently. This one my doctor warned me about. Even relatively slow can set it off sometimes.

lgfrie

dolorsit wrote: »

I keep reading that you should keep weight loss to under about 1%/week. Since Jan 1, I've been losing a bit over that at about 1.2% per week, half of which is a food calorie deficit and the other half is additional exercise (running and cycling). What might be the complications of losing weight too quickly, other than just putting it all back on again later at some point?

Thanks!

There are many complications. They range in severity from a bit of hair loss to heart failure (there is a person on this board who experienced the latter). Not every person will experience them, but the complications can be unpredictable, and sudden. It is extremely unwise to exceed the commonly understood limits for healthy weight loss.

One problem that is not unpredictable and is more like "definite" is, if you lose weight excessively fast, a decent portion of that will be muscle mass. Aside from this being not good for you, it will also slow down your burn rate, such that for the rest of your life, assuming you don't add muscle mass through serious resistance training, you will burn fewer calories every day forever. And not a trivial amount, either. You could end up with hundreds of less calories burned everyday, greatly increasing the odds - bordering on certainty - that you will end up in a regain situation, and this time without the muscle mass you used to have to make further weight loss manageable. This is not theoretical; it has happened to many many millions of people.

Aside from the above, you already nailed it - excessive rate of weight loss contains the seeds of its own demise. Deprivation leads to binging. There are so few cases of people who went on extreme diets AND KEPT THE WEIGHT OFF for it to be considered a near-certainty that it won't work. Can it be done for 20 lbs? Sure. What happens after the 20, though?

Be smart about it. 2 lbs per week or 1 % of your body weight, whichever is lower, is the max, unless it's a BMI > 40 situation under a doctor's care and supervision. To lose 2 lbs per week, you must eat one thousand calories per day less than your body wants in order to fuel itself, every single day with no breaks. That is aggressive weight loss. Anything more than that is not a good idea - and even the 2 lbs/week isn't really a great idea, tbh. It can work for a couple/few months but isn't a good long term plan.

dolorsit

oh wow, this is really interesting. Thanks.
I'm actually going down from BMI 30 (currently at 26.5 or so) and doing 4000-5000 calories of exercise a week. I guess the fact that my weight loss isn't giving me a problem with running, is a good sign that I'm not losing muscle.

However, I'll review my stats and find a good middle ground.

cwolfman13

dolorsit wrote: »

I keep reading that you should keep weight loss to under about 1%/week. Since Jan 1, I've been losing a bit over that at about 1.2% per week, half of which is a food calorie deficit and the other half is additional exercise (running and cycling). What might be the complications of losing weight too quickly, other than just putting it all back on again later at some point?

Thanks!

1% isn't a hard and fast rule, but it is a reasonably good recommendation for most. Kind of like 8oz glasses of water per day to stay hydrated might not be universal as hydration needs vary...but it's a pretty good starting point.

I've known people 300-400 Lbs who do indeed lose faster than 1%, at least for a time...but they also have massive fat stores, and their TDEE is such that even that cut in calories is still a reasonable number for calorie intake. The issue is when you cut calories to very low levels to achieve fast weight loss when you don't really have the requisite fat stores for it. At that point, you are starving your body of energy (calories) which are required for basic bodily functions...breathing...heart beating...growing nails and hair...like everything your body does requires energy.

When people dramatically cut calories to very low levels and or cut calories and over exercise, it is not unusual to eventually see thinning hair...hair falling out...brittle nails...loss of menstrual cycle, loss of muscle mass, etc. These are an indication of your body shutting down "non-essential" functions in order to conserve energy as they are energy "expensive". This obviously results in a slowing of metabolism...which would be the whole point of what your body is trying to do to better match what you're actually providing your body calorie wise.

AnnPT77

dolorsit wrote: »

oh wow, this is really interesting. Thanks.
I'm actually going down from BMI 30 (currently at 26.5 or so) and doing 4000-5000 calories of exercise a week. I guess the fact that my weight loss isn't giving me a problem with running, is a good sign that I'm not losing muscle.

However, I'll review my stats and find a good middle ground.

Be careful about using how you feel as a guide. I accidentally under-ate for a while when first on MFP, and felt great (energetic, not hungry, exercise performance good as a long-time active person) . . . until, bam, suddenly I didn't. I was weak and fatigued, took several weeks to recover. Actual loss of muscle mass? Don't know, maybe not . . . but no one needs even this.

I started losing at BMI around 30, joined MFP at about BMI 25. MFP underestimates my calorie needs, it turned out. I corrected quickly as soon as I realized I was losing too fast for my own good.

IMO, unless someone has acute weight-related health compromises, it's smart to err on the side of slower loss vs. faster loss. Slow loss can be frustrating, but fast loss can increase health risk.

Best wishes!

cwolfman13

AnnPT77 wrote: »

dolorsit wrote: »

oh wow, this is really interesting. Thanks.
I'm actually going down from BMI 30 (currently at 26.5 or so) and doing 4000-5000 calories of exercise a week. I guess the fact that my weight loss isn't giving me a problem with running, is a good sign that I'm not losing muscle.

However, I'll review my stats and find a good middle ground.

Be careful about using how you feel as a guide. I accidentally under-ate for a while when first on MFP, and felt great (energetic, not hungry, exercise performance good as a long-time active person) . . . until, bam, suddenly I didn't. I was weak and fatigued, took several weeks to recover. Actual loss of muscle mass? Don't know, maybe not . . . but no one needs even this.

I started losing at BMI around 30, joined MFP at about BMI 25. MFP underestimates my calorie needs, it turned out. I corrected quickly as soon as I realized I was losing too fast for my own good.

IMO, unless someone has acute weight-related health compromises, it's smart to err on the side of slower loss vs. faster loss. Slow loss can be frustrating, but fast loss can increase health risk.

Best wishes!

Just to add to this, if you talk to anyone who has experienced some of the negative side effects of rapid weight loss or significantly cutting calories to an unreasonable level, you will mostly likely find that they all say they felt fine...until they didn't.

dolorsit

Great advice. Thanks everyone!