Age is just a number. Nobody should let the arbitrary year they happened to be born in define them.
However, as you age your body changes - that's just science.
Here are some of the things that happen when you hit the big three-oh.
Slowed down metabolism
Ever wondered why as a teenager you could chomp down three bowls of pasta a day and not gain a pound?
Well, according to The American Council on Exercise, your basal metabolic rate will drop roughly one or two percent per decade.
As your body is producing less human growth hormone, turning 30 means your muscle tone will decline and you'll gain weight more easily.
Weight gain in the early thirties is also largely due to the majority of people that age having sedentary jobs, leading to them burning fewer calories. The American Council on Exercise also says that the number of calories you burn a day decreases by around 150 calories per decade.
That might not seem like a lot but it adds up. There are roughly 3,500 in a pound of fat. Assuming your diet stays roughly the same between the ages of 20 and 30, 150 fewer calories burned a day would lead to an extra pound gained every 23 days - or 16 pounds a year.
Other lifestyle factors also drive up stress, leading to a release of hormones which encourage you to store fat.
Decreased libido for men, increased libido for women
Turning 30 can lead to a decreased sex-drive due to lower levels of testosterone in men. This is mostly due to lifestyle stresses rather than ageing.
Men's libido decreases about one per cent every year, according to Livestrong.
On the contrary, women's sex drive actually increases.
According to a study from the University of Texas, women aged between 27 and 45 are significantly more sexual compared to those in their early 20s.
Women's fertility starts to decline around 30, by 32 a woman’s fertility rate begins to decrease gradually and by 35 the decline falls faster.
Equally, male fertility begins to drop, and sperm mobility decreases continually between the ages of 20 and 80, meaning it can be harder for couples to conceive.
But it's not all bad, you might actually be happier
Around the age of 30, our personalities are more settled and and people are more comfortable with themselves.
The cerebellum is still developing well into the early 20s - due to that and life-altering experiences, people tend to be more comfortable with who they are by the time they reach 30.