Obesity and cancer third most important risk factor for cancer in the United States, just behind tobacco and diet (see Figure). Obesity is the source of about 15% of all preventable cancers. In 2018, Chinese researchers performed a systematic review and comprehensive quantitative meta‐analysis of cohort studies reporting body mass index (BMI) and the risk of 23 cancer types, providing epidemiological evidence supporting the association between BMI and cancer risk. The strongest positive association between BMI and cancer risk was found among patients in North America. The mechanisms by which obesity may increase the risk of cancer are not well understood, but it
Tropical rainforest Tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as "lowland equatorial evergreen rainforest". True rainforests are typically found between 10 degrees north and south of the equator (see map); they are a sub-set of the tropical forest biome that occurs roughly within the 28 degree latitudes (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). Within the World Wildlife Fund's biome classification, tropical rainforests