The Robert Koch Institute (RKI), the Berlin-based government health agency, made the discovery after doing two four-year studies, one in the late 1990s and the other between 2008 and 2012.
The results showed that not only were more people obese, but the number of obese young people had risen significantly.
In 1998, 19 percent of men and 22.5 percent of women had a BMI of over 30 – which officially defining them as obese.
By 2012 though, this had climbed to around 23 percent of both men and women.
“The number of young adults who are obese has gone up particularly,” said study director Bärbel-Maria Kurth on Thursday. She added that the team found that the higher a person's wage or academic qualifications, the less likely it was that they would be obese.
This part of the results prompted Health Minister Daniel Bahr to say that measures to prevent obesity must be targeted at specific demographic groups. He explained that previous campaigns to raise awareness of being overweight have worked for the higher-earners, but been less successful in talking to other social groups.
While obesity levels have risen, the amount of people classed just as overweight has decreased slightly, with 67 percent of men and 53 percent of women boasting a BMI of over 25.
Germany's widening girth is having a knock-on effect in other areas of the nation's health. Diabetes, for instance, is on the rise.
The study, which assessed 7,000 over-18s both times it was carried out, found that the percent of Germans suffering from the disease has risen from 5.2 percent to 7.2 percent. Groups most affected seemed to be women under 40 and men over 70 and 4.6 million people now live with diabetes in Germany.
Interestingly though, the number of Germans who told the RKI that they were doing exercise at least once a week had gone up considerably since 1998. Nearly 52 percent of men and 49 percent of women said that they worked up a sweat regularly.
But despite best efforts, only half of men and less than 15 percent of women who said they were exercising were meeting the World Health Organisation's recommended weekly amount – 2.5 hours.