Some people just don’t look their age. Sometimes they look young, and sadly sometimes they look old. We — especially those of us who are women — are bombarded daily by ads for products that are supposed to make us look younger, but what exactly does that mean? What makes someone look old?

A recent study of 102 Danish twins and 162 British women set out to ask those questions. They found that some of the things that make people look old are obvious, like grey hair and wrinkles. Others were more subtle, such as lip height and receding hairlines. Here’s what the researchers had to say:

Hair graying, recession of hair from the forehead and lip height were influenced mainly by genetic factors whereas environmental factors influenced hair thinning. These findings indicate that women who look young for their age have large lips, avoid sun-exposure and possess genetic factors that protect against the development of gray hair and skin wrinkles. The findings also demonstrate that perceived age is a better biomarker of skin, hair and facial aging than chronological age.

Now, obviously many of these factors are inherited and largely out of our control. However, there are things you can do to help look younger. The most important of these is right there in the quote: avoid sun exposure. Avoiding excess sun will also put you at lower risk for skin cancers. Wrinkles are easier to prevent than to fix, but a combination of avoiding sun exposure and the regular use of moisturizers will help. Some wrinkles can be made less visible with treatments such as photo-facials, chemical peels, fillers, or Botox. It is also possible to do something about gray hair, as long as you don’t mind regular use of hair color. For those who are concerned about harsh chemicals, temporary colors, rinses, and henna preparations will also work.

We talk a lot about how your food and activity choices can effect how you age. Few of these things will actually help you live longer, but they will help you look younger as you age.

Her Take: I am one of those lucky ones who looks young. I was carded almost up to the day I turned 40. Some of it is genetic factors, but I still try to take good care of my skin and use a moisturizer with sunscreen every day. I also go very light on the make-up, because it can make you look older. However, a good quality foundation that is the right type for your skin can hide sun damage and other imperfections.