Overweight and obesity have become a serious health concern in Western countries from the 1980s. Numerous weight management strategies combine lifestyle modifications regarding diet and exercise with dietary supplements. Coffee extracts, caffeinated or not, have been used as weight-reducing nutraceuticals for more than 15 years. However, few clinical studies have been performed and several clinical biases do not allow easy conclusions concerning the biological effects of this food. Meanwhile, many in vivo, in vitro or epidemiological studies have pointed out that coffee, caffeine, decaffeinated coffee or chlorogenic acids could be used as slimming agents. This chapter reviews and discusses results which could explain caffeine, coffee or decaffeinated coffee effect on body weight. Epidemiological, in vitro, in vivo and clinical studies which could explain the slimming effect were reviewed and putative mechanisms of action involved in different works are discussed.