There are a number of reasons to keep your weight in check that you're probably already aware of -- like heart disease, joint problems, and even cancer; all of which are often linked to diet and exercise. However you might not know that many eye diseases are also influenced by physical fitness.

Obesity is thought to be associated with cataracts, macular degeneration, and glaucoma -- all of which can be caused by weight-related issues, such as high blood pressure, diabetes and lack of exercise.

To combat these problems, it's important to be physically fit, and to make sure you're getting enough lutein (which protects the eye against macular degeneration) and zeaxanthin (which protects your retina from light damage) -- both of which are easily found in everyday foods, like egg yolks.

So take this as yet another reason that you should be eating right and staying active.