However, studies on twins support the existence of an important role of susceptibility genes. Environmental factors would then act to unmask latent tendencies to develop obesity. The role of such factors has been evidenced by time trends in obesity as well as studies on migrant populations. Undoubtedly, the best public health approach is to prevent obesity, keeping in mind that a progressive fattening of the population is not inevitable. This requires education on healthy diets and encouragement of lifelong, regular exercise.
Much research is still necessary to clarify what a healthy diet is.
Every year there are about 160,000 new cases of colon cancer in the USA with 58,000 fatalities, making this form of cancer the second most common cause of cancer deaths. Several lifestyle factors have been implicated in colorectal carcinogenesis. These include diet, smoking, alcohol consumption, sedentary habitudes and obesity. Several epidemiologic studies have shown that weight gain in middle age leading to abdominal obesity increases the risk of colon adenomas, and consequently of colon cancer. Overweight has long been recognized as a risk factor for hormone-related and other cancers such as colorectal cancer.