Want to lose 30 pounds before turning 30

Hi! I'm 5'1 too. 35 years old. Started at 150 pounds, currently at 117. It took me a year and change at a defecit of 0.5 pounds/week. Sometimes I lost 1 pound a week (in the very beginning), sometimes less than 0.5 pound a week. A year isn't a long time in the span of your whole life, but when it comes to weight loss we tend to think it is too long. It's not.

What you're proposing sounds like you want to do something very difficult and suffer for 6 whole months for what would very likely amount to only a few months at your goal weight before you potentially gain it all back. Weight loss isn't psychologically easy so why make it harder on yourself by restricting your timeline? Weight loss isn't linear either so, try as you might, you won't lose 6 pounds a month every month, sometimes it'll be less, especially the closer you get to your goal. It took me 5 months to lose the last five pounds.

Imagine yourself having acheived your goal, but by the time you turn 31, you're back at your current weight because you didn't learn how to make the loss sustainable and didn't create the necessary new habits to keep you at your desired weight. You'd be back here again in a year and having to go through the whole cycle again. That's a risk you're taking with rapid weight loss and it's not one that's guaranteed to be fun or empowering.

A more sustainable goal might be losing 30 pounds by the the time you turn 31. Or if you want to make it sound cute, "lose 31 pounds by age 31." You can start that by breaking your weight loss up into small chunks so you can feel successful regularly and more than once. Set your first goal to lose just 10 pounds. Take your time. It's okay to be 140 pounds by the time you're 30 because if your goal is instead to be 125 pounds by the time you're 31, you're already well on your way. If you can keep it up, hopefully, by the time you're 32+, you've learned how to stay at 125 or whatever weight you want to be. Getting to your goal eventually is better than risking not getting to it at all or getting to it but only for a little while.

Don't make things harder for yourself. Putting tons of pressure on yourself isn't going to help you stay accountable because life will get in the way which will test your resilience and commitment. If you're going to be successful long term, you'll need to learn how to build habits that allow you to get closer to or stay at your desired weight despite whatever hardships and temptations come up. Habit building takes time and it requires things to be easy and convenient to do so that you keep doing them. Make weight loss psychologically easy and logistically convenient and set a realistic timeline and you'll create the habits to keep you successful for a long time to come. Good luck!