Right now I am on a very strict diet. ~1000-1300cal. I am 5'11" and 195lbs currently. So far its going pretty well. I keep an ok protein intake. About 40-60g per day from various sources.
Going to the gym, weights 3-4x per week and biking or ergometer otherwise.
Will I see muscle loss from the reduced calorie intake or lack of protein? What else can cause muscle loss? Under what conditions?
I plan to continue this diet until I am 185lbs. I have been on it from 206lbs.
Then I am taking a break, and doing it again. I am at 21% BF and plan to get to about 15% before I re-bulk... properly.
How old are you?
I won't beat around the bush either, so here goes..
1000-1300kcals is not a diet; it's starvation.
40-60g of protein per day? I inhale that much just looking at my breakfast. 50g of protein is what, 200kcals?
Yes you will experience muscle loss and probably won't lose more that 4-6lbs of fat--IF YOU'RE LUCKY--if you do this 'diet' for any length of time.
Next, you said you are going to "take a break". Don't you see the fundamental flaw in your thinking? People should not have to starve themselves or treat their body's so poorly just to get healthy.
Want to know exactly what's going to happen to your body in the coming weeks if you continue?
You're going to experience weight loss. You will lose muscle and perhaps a small amount of body fat. I'd hazard to say on the order of a 4:1 ratio, muscle:fat.
You're going to start feeling lethargic and your willpower will start to erode as you lose belief in this program. Perhaps you have iron will and you will keep starving yourself. Eventually you will be what's known as Skinny-Fat. You will look skinny, but still look flabby.
You will lose faith in your masterplan and give up on your dreams of having a fantastic body.
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What I said above is a distinct possibility, but it doesn't have to become reality.
Here are a few iron curtain rules that you should take with you to the grave.
1. 1-2g of protein per lb of bodyweight. Eat that every day.
2. Never go below 1500kcals. For you, I wouldn't go below 1900-2000.
3. 75-150g of balanced fats. Eat that every day. By balanced I mean eat a variety of: saturated, monounsaturated, omega 6, and omega 3 sources.
4. Use carbs sparingly and only when your body needs them. Keep your carbs low GI. Apricots, apples, and berries are all good choices. For grains, stick to rolled oats, brown rice, and potatoes.
5. 4L+ of water. Drink that every day.
6. 10g of fish oil. Take that every day in the form of capsules or fresh fatty fish.
7. Weight training. Do it 3-5x per week, varying intensity. Mix your rep ranges. Some days do 1-3, other days 4-6, other days 8-10, other days 10-15.
8. Cardio. Do it 4-6 times per week, BEFORE breakfast on an empty stomach. Moderate pace for 45-60 minutes.
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There are plenty of good articles in the sticky that you should read. What I wrote here is very brief, lacking in explanation, and too simple for modern man to take seriously.
One last thing.. WHEN you get a body that you're proud of, keep it for at least 6 months before doing anything different.
You'll know when you're doing the right thing. You'll get a feeling that you LIKE what you do day to day, rather than doing something that makes you feel bad.