I had been lifting for several years before I started using it and I noticed it had a minor-but-noticeable effect on my ability to lift; I could get maybe 1-2 more reps and maybe go up in weight a little bit. I think it may have also made me look a little bigger than before. So it's a very minor effect compared to the difference you'll see from actually starting to track your calories and go to the gym. But it's better than not having it.