Leaving aside the cosmetic problem of being over-weight, you should know that obesity is the commonest predisposing cause, for the following problems:

Diabetes Mellitus (Excess blood sugar)
Hypercholesterolaemia (High Blood Cholesterol)
Hypertension (High Blood -Pressure)
Ischaemic heart disease (Heart attack)
Osteoarthritis of weight bearing joints (Hips, Knees & Ankles)
Lumbar and Cervical spondylosis
Varicose veins (dilated, tortuous veins in the legs)
Hernais, particularly incisional hernia, after abdominal operations
Gall bladder stones.