How bad are 1000 cal deficits, really?

I'm going to get some popcorn cooked. The replies on this one are going to be great and I've got a front row seat

What are your height/weight? A 1000 calorie deficit is fine if you have 75+ pounds to lose. After that, you run the risk of losing muscle mass along with fat.

If your doctor okays it and you feel healthy and strong, there is no reason to eat more than 1600 calories a day.

Everyone is different. You have to do what works for you!

Is this deficit a TDEE thing? I don't even know what my TDEE is, so IMO, it's not that important.

I used to run a 500 calorie deficit @1800 daily, and often hit only 1400-1500 (sometimes 900-1200 adding cardio time) so I switched over to a 750 deficit and still manage to hit my daily macros (30% protein, 45% carbs, 25% fat) without any side effects. I feel good and full (both hunger wise and energy wise) . I don't believe it will hurt you as long as you don't skip a meal and double up for it later (which I happened to do and binged on 12 oz. of breaded chicken breast , completely going over my 1400 daily limit)

I've been running a 1000 calorie deficit for a month and a half now and overall I feel great and have more energy than I ever have! I am only consuming 1600 calories a day, and generally take in 100g of protein, 54g fat, and around 130-150g of carbs.

I keep reading that people are referring to 1000 cal deficits as "starving yourself", but truthfully I just don't understand it. Are these people not eating enough protein?

As long as you are doing some vigorous weight training, it's probably fine. Keep in mind that eventually, if you lose enough weight, that approach will no longer work.

An analysis of the Minnesota Starvation Experiment data suggested that a sedentary person can mobilize at most 31 calories per day per pound of adipose tissue (http://www.ncbi.nlm.nih.gov/pubmed/15615615). Although others have pointed out the limits to that analysis, it does stand to reason that there is an upper limit to the amount of calories that a healthy person can draw from stored body fat before the body also starts to consume lean body mass to fuel itself. An obese person most likely doesn't need to worry about a 1000 calorie deficit, but if your body fat percentage is relatively low, it makes sense to lose weight less aggressively.

I'm 5'8 and weight around 150 lbs. I haven't weighed myself in a few months so I could be lower than that, I wanted to give myself some time between weighs.

I suppose I'm coming from a weird place, as even before this calorie watching I wasn't eating a lot of food, the food I was eating was unhealthy and high in calories however. Now that I've changed the quality, I seem to have no problem with the quantity. Being 150lbs at 5'8 doesn't really put me at much weight to lose, so I don't plan on doing this forever.

My goal is to combine this with intermittent fasting to get the fat off, and then I'll be looking to bulk.

A 1000 calorie deficit sounds far too aggressive for your goals, and you run the risk of losing quite a bit of muscle along with the fat. A half pound per week goal combined with adequate protein intake and heavy lifting is more appropriate for what you want to do.

Back to your initial question, a 1000 calorie deficit in and of itself is not bad, but it is more for people who have 75+ lbs to lose. When people here talk about people starving themselves, they are usually talking about a 1000 calorie intake, not deficit, because that calorie goal is too low for most people and it is difficult to get proper nutrition. That's not to say that having a deficit that is too aggressive does not have its drawbacks as well, just wanted to highlight the difference between calorie goal and deficit.

Maybe you don't burn 2600/day. Have you lost 12 lbs. in the last 6 weeks? If not, then you burn less than you think or you're eating more than you think.

With as little as you have to lose, I'd be surprised if you're able to lose 2 lbs/week reliably for that long. It's hard when you're not obese, and really hard when you're not even overweight.

dingdingdingdingding!

Maybe you don't burn 2600/day. Have you lost 12 lbs. in the last 6 weeks? If not, then you burn less than you think or you're eating more than you think.

Personally I find it a bit on the low side, and I'm sure I'm going to lose more than 2 pounds per week on 5000 kilojoules! Time will tell, I suppose

Given your stats?? Sounds like a bad idea, to me. A train wreck. And, I'd eat more fat.

I've been playing around with a few calculators, including MFP for goals, and either way I change things up I always seem to be told to eat around the same amount of calories.

The fact that the excercise levels are so general doesn't help. There's a 400 calories difference between light and moderate activity level.

If I bring my goal down to 1lb a week, and change my fitness level to low (assuming I don't burn 2600 calories), I still end up howevering around 1750 calories a day which isn't too much more than the 1600 I'm eating now.

How would you classify 5 days a week in the gym lifting weights for an hour each day? Light activity, moderate? I do computer work when I am not at the gym or walking around so I'm having a hard time telling these calculators what to do.

weight training is more on intensity level. There is no set level. Weight training does not really burn that many calories,

Unless I missed something, I think you state that you are male 5ft 8 in and 150 lbs. Why in the heck would you want to lose weight? If you want to gain muscle or increase fitness level overall this seems reasonable but you weight is considering in the low/middle range for women of your height.

Probably because he's 16 and emo, rather than 26.

If you feel great and the weight is coming off slowly, just keep up the good work. If you stop losing at all, just up the exercise and cardio slightly till the weight starts coming off again.