Recently I've started working at the Supermarket, in the checkout section. Lame I know, but it pays well whilst I'm at Uni, and the experience is awesome. Having to start a conversation and make a new friend every 10 minutes has given me a lot of confidence.
Having a passion for health, and studying Nutrition I pretty much know the nutritional and energy value of most things in the store. So when people come through the checkout, without even looking at the customer I could tell you what the customer looks like by they have by the foods they've bought.
You're probably sitting there going "duh, donuts make you fat, etc", but its more than that. People that come through with a lot of fresh vegetables and whole grains just look healthier, they're also often happier and more willing to chat. Their skin glows, their hair is healthier, everything.
Another thing I've noticed is smokers. Due to recent law changes, banning smoking in pubs and clubs, most younger smokers have quit, but the older one still buy them. It is painfully obvious which ones smoke, their skin is terrible, they're wrinkled, they look older than they actually are (well, I don't ask their age, but you can often tell a persons age by the age of their friends, partner or kids), and a ton other minor differences.
Just something I thought you guys might find interesting. Next time you're at the Supermarket have a peek at other people's trolleys and see if they relate to the person's size/health.