The 25-year-old, who battles with Type 2 diabetes, reported to training camp weighing just 203lbs compared to 219lbs last season following a summer of strict diet and exercise.
That has seen a change in attitude from opposing coaches this season, says Peterson.
Peterson has been thrown at just 12 times through the first four games, allowing just 85 passing yards – the fifth best in the NFL this season for cornerbacks who played at least 60 percent of their team’s defensive snaps.
“I feel now that I’m in a position that I wasn’t in last year to make those plays because I felt that I was just a little bit too heavy,” Peterson added.
“As a cornerback, you have to be as light as possible on your feet. You have to make sure you have fluent hips and a great change of direction.
“When I put that weight on last year, I wasn’t able to do some of the things that I wanted to do in the year prior. So now that I am down to my lowest weight since I’ve been in the NFL, I feel unbelievable.”
However, Peterson is keen to assert that increased athleticism alone cannot explain his outstanding early-season form.
“I think now that I am in year five [with the team], I feel like I really, really turned the corner this year.
“I believe that I had an eye-opening year last year relying on athletic ability seven out of 10 times on the field. Now, it’s all mental.
“I definitely take my preparation more serious than I did over the past first four years. I think that’s the biggest difference.”