Why on earth would you starve yourself down to 150? I personally haven't weighed 150 since I was 13. I can't imagine being that thin.
By starving yourself, you train your body how to be a fat-storing machine, which is an idiotic thing to do. That's why fat people fail so badly on repeated diets, and then make excuses about having bad genes, being full-figured, big-boned, etc. They train their bodies how to be fat-storing machines via caloric deprivation, eating the wrong things, at the wrong times, and having meal sizes that are to large at each sitting.
On one hand, and I have to be honest here, being underweight (if you're sedentary) can help you live longer, but, on the other hand, the more muscle you build the easier it is to stay lean because every pound of muscle gobbles up calories just sitting there, and you'll have all the benefits of being a machine that's well-oiled, sexy at the primal level, and not "rusty." One should not just go off and die, as so many fat folks to, at age 18, or even before. That's a waste of a good body. Use it, or lose it.
It's always in your best interest, barring a medical condition, to engage in resistance exercise. Your bones will be stronger, your brain will work better, you'll have a higher base metabolism (resistance exercise is the ONLY exercise that does that), and you'll grow stronger, and more muscular, AS YOU GROW OLDER. Don't hinder what should be a natural process by not eating, and engaging in needless weight management. Let your body do what it wants to do on its own under a positive stimulus: grow.
Anything worth doing should be worth doing well, including lifting weights / resistance exercise.
Don't worry, you won't get to big (LOL). That takes time, money, genes, smarts, desire, and a lot of hard work, which most folks can't muster.
Remember: more muscle = a faster engine. A faster engine means it's easier to stay lean, and you burn more calories. Strong bones, a good brain, a good heart, are all great side effects. It's just a common sense thing when you study the science of it all.
And, while some are quick to make the disclaimers of "I don't wanna' be big", and so on. Many folks are attracted to hunky vs skinny. That's not delusional...that's primal, and hard-wired into our brains.
Some things you have to understand about folks on mags:
1. These guys train all day.
2. They take the best of the best meds / supps, and know how to use them.
3. They only look like that for a few days at a time.
4 They are genetically gifted in many cases for a certain look.
Balance. Wax on, wax off.
Looking like your reside in a third world country isn't really something that I would do, but, it's your game, and you play it as you will.