The estimated number of people with type 2 diabetes worldwide was approximately 415 million people in 2015, and that number should reach more than 642 million in 2040 (IDF Diabetes Atlas, 7th edition), thus prevention of type 2 diabetes is a major challenge for public health professionals throughout the world. In Japan, approximately 7.8 million Japanese were estimated to have type 2 diabetes in 1990, and the number gradually increased to reach more than 22.1 million in 2007. Subsequently, however, the number decreased though by a small margin, and was estimated to be approximately 20.5 million in 2012 according to the Ministry of Health, Labor and Welfare. The apparent break in the rise of the prevalence of diabetes in Japan is probably related to the tokutei kenshin, formally called tokutei kenko shinsa; that is, annual medical check‐up, which was legislated in 20081, 2, 3. The tokutei kenshin is an annual medical examination in Japan that was established with a special focus on metabolic syndrome, namely visceral fat syndrome. Under this system, when the results of clinical examination and laboratory tests show that the examinee has or is at high risk of metabolic syndrome, s/he receives assistance in reviewing her/his lifestyle for improvement (specific health guidance), which is called tokutei hoken shido. The purpose of this educational program is lifestyle intervention that can lead to prevention of potential lifestyle‐related diseases, such as diabetes, hypertension, dyslipidemia and cardiovascular diseases. Type 2 diabetes results from both genetic predisposition and environmental risk factors, such as obesity, visceral fat accumulation and physical inactivity. Therefore, lifestyle interventions, especially those designed to reduce bodyweight, are thought to be effective in preventing or delaying the onset of the disease. In fact, several large‐scale intervention trials in the USA and Europe have concluded that lifestyle interventions designed to reduce bodyweight prevent or delay the onset of type 2 diabetes in subjects with impaired glucose tolerance (IGT). However, most of the participants in the aforementioned studies were obese, and especially in the Diabetes Prevention Program4, the mean body mass index (BMI) of the participants was more than 30 kg/m2 at baseline, which makes them very different from the Japanese population. One Japanese study5 that analyzed the correlation between weight reduction and change in glycemic control in men suggested that bodyweight reduction is an effective strategy for prevention of type 2 diabetes in men with visceral fat accumulation. The study showed that in Japanese men with glycated hemoglobin (HbA1c) levels of 5.6–6.4%, who are considered prediabetics, reduction in bodyweight within 1 year correlated positively with the change in HbA1c in men with visceral fat accumulation, but not in those without visceral fat accumulation, irrespective of BMI (whether BMI was ≥25 kg/m2 or not). This suggests that weight reduction could be effective in preventing diabetes, especially in individuals with visceral fat accumulation, and that assessment of visceral fat, rather than BMI, seems more important in identifying those individuals that would benefit most from lifestyle intervention. In this context, the tokutei hoken shido, which focuses on metabolic syndrome (visceral fat syndrome), is reasonable and should be effective in preventing diabetes. Then, to what extent should bodyweight be reduced to prevent the development of type 2 diabetes? In the Diabetes Prevention Program in USA, a randomized clinical trial designed to prevent the development of diabetes in patients with IGT4, the incidence of type 2 diabetes was reduced by 58% after 2.8 years with an average weight reduction of 5.6 kg (loss of approximately 6% of bodyweight) in the intensive lifestyle intervention group compared with the placebo group, with an average weight loss of 0.1 kg. In the same study, loss of more than 5–7% of bodyweight reduced the risk of type 2 diabetes by more than 90%. Similarly, a Japanese observational study6 showed that in Japanese men with visceral fat accumulation and HbA1c level of 5.6–6.4%, a weight loss of ≥4.3% significantly reduced the risk of diabetes by approximately 80% compared with the bodyweight gain group (mean weight gain, 2.8%) during the 3‐year study period, whereas weight loss of