This is according to a survey carried out by the South West News Service, which worked out the average age at which various signs of ageing appeared among adults across the UK.
While a couple of signs first arise in people’s 20s, there's no escaping the trend – most types of physical change take place in their 30s.
And the pattern is reflected in the way we feel – most of the people questioned said they felt healthier in their 20s than in their 30s, with poor diet, lack of exercise and excessive consumption of alcohol being the main culprits of a decline in health.
"The research shows by the time we reach our thirties, everyday ailments like joint pain, headaches and digestive problems are more common place,” one of the researchers said.
Even those who have kept up a fitness regime throughout their twenties are often set back by problematic ankles, knees and backs.
Although their lifestyles might not always show it, Britons are concerned about the state of their health. The survey revealed that the main issues on their minds are the health of their hearts, memory problems and high stress levels.