"Hey, I am interested in getting a tattoo on my outer upper arm, but it goes to part of my inner arm. I have light stretch marks on the inside of my arm and I am about 35 pounds over weight (but I am on my way down); could this affect my tattoo?" -Luke
I'm kind of in the same situation as you - I've been losing weight, but I've got a lot of stretch marks that I don't think will ever completely go away. Even though I still have more weight to lose, I went ahead and got my arm tattooed.
First, I'm very pleased with how nicely the tattoo ink covers the light stretch marks. It was, however, very painful getting tattooed in this area because the skin is loose and thin. I would swell and bruise after each session, but it healed nicely and now it's beautiful.
Even if I lose more weight, my arms aren't going to change that much and I'm guessing that will probably be the same for you. As long as you don't get anything with tiny details all very close together, you should be fine. The tattoo will shrink and adjust as you lose weight, but even 35 pounds will cause very little change in your arm. Even if you work out and bulk up the muscle in that area, your tattoo should handle it just fine. Just be sure to communicate with your artist what your plans are so they tattoo you with these changes in mind.