Coffee is a natural product, with high quality coffee having zero additives in it. It also contains caffeine. Caffeine is known to help mobilise fats from your bloodstream and increase your metabolism. It does this by causing adrenaline to be released which travels through your blood straight to your fat tissues, causing them to break down and release the fats.
However releasing fatty acids into your bloodstream does not cause you to lose weight unless you are consuming less calories than you burn. Just because the fats are there does not mean they will automatically be burnt up. There are studies showing that caffeine increases your resting metabolic rate by 3-11%. However in the long term people build up a tolerance to caffeine and this stops working. One study showed that caffeine increased fat burning by as much as 29% in lean people but only about 10% in obese people. The effect also appears to decrease with age and is greater in younger individuals.
Caffeine's affect on energy levels could also help you to lose weight. Caffeine inhibits the receptors responsible for tiredness. This helps you to feel more energised and able to exercise which will contribute towards weight loss.
If you cut out the sugar in your drink a cup of coffee is relatively low in calories, (about 15-20 calories with milk, and less without). This is much healthier than fruit juice or other sugary drinks. Drinking it wont miraculously shrink your waistline but it also won't add to it!
So coffee alone can't make you lose weight. It can however help you to lose
weight when combined with a healthy diet and regular exercise routine.