1. A decrease in muscle mass
5. Brain may not feel as happy as it used to
9. You may notice thinning hair
Science suggests that turning 40 may be one of the best things that ever happen to you. An Economist report, for example, found that people's happiness and life satisfaction rose sharply after turning 40 [1].
Most people have established themselves professionally by turning 40, have perhaps settled down with a significant other, and are enjoying family life - it is entirely fine if one does not desire those things.
The fact is that your body undergoes a significant physical shift when you reach 40, and some of it goes beyond just 'a slower metabolism.' Find out what happens to your body and physique when you reach 40-years-of-age.