8 week challenge at Orange Theory

I am weighing in today at my local gym.  There is an 8 week challenge that I've entered that runs to 3/17.  I typically do low carb, but since the holidays have let potatoes, no grain bread and desserts back into my way of eating.  I'm going to go strict keto.  I have approximately 40 pounds to lose.  I am 58 years old, and turn 59 in May.  I'd like to lose 10 to 15 in the 8 week challenge, and another 10 to 15 by my birthday.  We go on vacation to the beach in August.  I'd like to be real close by then.  I'm in the 190's, and am 5'6".  My ultimate goal is 155 lbs, or whatever weight my body is comfortable with when I get there.  

I've done WW before and I know that doesn't work.  Last year I did Whole 30 and that was when I learned about inflammation, etc. and the benefits of low carb.

Anyways, thanks for reading if you got this far.  I hope this is a welcoming and friendly forum.