Unfortunately, I’m both. Keeping my calorie intake below 1000 just slows down the rate of gain. At one point I managed to get my intake below 450/day for 2 weeks, but that isn’t something I can do long-term.
Intermittent fasting, not starvation, is the better approach. I eat 600 calories on Monday/Thursday and 1250 the other days. Staying too low for too long signals starvation and a conservation metabolism takes over. My calorie targets on the 1250 days are aimed at sufficient protein for my lean muscle mass. 93 grams gets the job done. I shoot for 30% calories from protein, 40% calories from carbs, 30% calories from fat. My lean body mass and activity drive the protein target. The proportions hail from the "zone" diet. (93 x 4) / 0.30 = 1240 calories total. (1240 * 0.40) / 4 = 124 grams of carbs. (1240 * 0.30) / 9 = 41 grams of fat. I put those targets into MyFitnessPal and track everything I eat during the day. When I hit my targets, I stop eating for the day. The numbers are proportionately reduced for the Monday/Thursday timeframe.
There are lots of good electronic scales that will give you body fat % and water weight to track proper hydration. You can derive your lean body mass from the scale and set personal targets suitable for your own configuration. Protein sufficient is the aim. Shorting protein can have adverse effects on your heart.
I'm currently 17% body fat. At 145 lbs, it was 13.7%. Women need a higher body fat percentage to be healthy.