Some thoughts on "starvation mode". Eating one 1000 calorie meal will not put you into this but eating that way for several days will.
I, personally, think that varying the number of calories consumed is OK as long as one doesn't consistently go over the number of calories burned or under the number needed for basic metabolism. If under one will burn muscle.....not good! If over one will gain.
For me, it seems to work best if I keep my calorie level at 10x goal weight. I try for 70% fat, 25% protein, and 5% carbs.
I usually am around 1300 to 1400 cals.