The American multi-eventer, hailed by sprint king Usain Bolt as the world's greatest athlete, said his exploits had left him this year "feeling physically worn down".
"I feel like a little bit more fragile this year for some reason," Eaton, favourite to win gold at the world championships in Moscow, told a news conference at the Luzhniki stadium on Wednesday.
"I'm usually pretty robust, nothing really bothers me too much. This year, little things have here and there ... and my coach said the year after the Olympics you are kind of physically worn out.
"You see a lot of Olympic champions that are not at this (world championships) meet because it does take a toll on mind and body."
Eaton produced sensational form in 2012, setting world records in the heptathlon at the world indoor championships and also in the decathlon at the U.S. Olympic trials.
In rain-soaked conditions in Eugene, he became only the second decathlete to break the 9,000-point barrier as he eclipsed the previous mark set by Roman Sebrle with a haul of 9,039 points.
Eaton went on to claim Olympic gold in London with 8,869 points.
After a three-month layoff he returned to training in November, the 25-year-old not expecting to feel as sluggish as he did.
"It took longer to get moving and warm-up," he said.
This season he has mixed "a few personal bests earlier this year" with an injury scare when he tweaked his hamstring during high jump practice.
His preparations for Moscow, though, are back on track, and Eaton said he was in great shape in his bid for a first world title after taking silver behind compatriot and two-time winner Trey Hardee in Daegu, South Korea, in 2011.
"I feel ready to go. If something was going to happen (injury-wise), it would have," he said.
The two-day decathlon gets underway on the first morning of the championships on Saturday.
Away from the track, Eaton married Canadian heptathlete Brianne Theisen in Eugene in July. The pair met as teenagers at the University of Oregon.
"I'm way more proud of her than I am of myself, and she vice-versa for me," he said.
"It's cool to be in the same events, to be successful at the same time and be able to travel around the world together."
Theisen was 11th in the Olympic heptathlon in London but showed she could be a medal contender in Moscow after winning the prestigious Hypo meeting heptathlon in Gotzis, Austria, in May.
(Editing by Stephen Wood)
