Moderate to vigorous physical activity is associated with improving insulin resistance in overweight and obese adults. However, effect of light physical activity on insulin resistance remains to be fully elucidated. The purpose of this study was to investigate the effect of light physical activity on insulin resistance in overweight and obese men. Thirty-seven overweight and obese middle-aged men (28.9 ± 1.8 kg/m², 51.0 ± 8.8 years) participated in this study. They took part in the lifestyle intervention (calorie restricted diet and exercise) for 12 weeks. Anthropometric parameters, fasting glucose, HbA1c, fasting insulin, and HOMA-IR were assessed at baseline and post intervention. Physical activity was objectively measured using a triaxial accelerometer at baseline and during intervention. Light physical activity (+17.7 min/day) and moderate-vigorous physical activity (+33.2 min/day) increased significantly, while body weight (-12.4 kg), fasting glucose (-9.5 mg/ml), fasting insulin (-4.2 μU/ml), and HOMA-IR (-1.1) decreased significantly. The change in light physical activity from baseline to during intervention were inversely related to change in fasting insulin (r = 0.18, P = 0.02) and change in HOMA-IR (r = -0.16, P = 0.03), after adjustment for several confounders. These results suggest that an increase of light physical activity improves insulin resistance in overweight and obese men.

This study described 1-year changes in body weight and metabolic syndrome components in middle-aged obese Japanese men participating in a 6-month weight loss program. This study comprised two phases: 6-month weight loss program and 12-month weight maintenance. Data were collected at Tsukuba, between July 2009 and February 2011. Overweight or obese Japanese men aged 40-64 years without any cardiovascular disease history participated. The primary outcome was the 18-month weight change. Secondary outcomes were 18-month changes in metabolic syndrome components. Primary analyses included all participants who had provided baseline data, and all missing follow-up values were replaced with their baseline data. Of the 58 participants, 39 (67.2%) completed all measurement visits. Their body weight decreased significantly immediately after the 6-month weight loss program (-8.0 kg; 95% confidence interval [CI]: -10.2 kg, -5.8 kg). However, it increased significantly, by 3.7 kg (95% CI: 1.4 kg, 6.0 kg), at Month 18 (a year after the program ended). The 18-month weight loss was 4.3 kg (95% CI: 2.1 kg, 6.5 kg). Among the metabolic syndrome components, visceral fat area, systolic blood pressure, and high-density lipoprotein cholesterol levels improved significantly at Month 18. The other components did not improve over the 18 months. In this study, the obese, middle-aged Japanese men experienced modest weight regains after its substantial reduction. Unlike other ethnicities, factors associated with long-term weight loss maintenance remain understudied among Japanese adults. Therefore, accumulating evidence from Japanese studies with longer follow-up is necessary in the future.

It has been reported that physical fitness of breast cancer patients is relatively lower due to the cancer treatment such as surgery, chemotherapy, or endocrine therapy. Previous studies have revealed that not only cardiorespiratory fitness but also muscle strength is lower among breast cancer patients than no disease women and these symptoms may aggravate the health-related quality of life. However, there is no study which has focused the physical fitness level in Japanese breast cancer survivors. The purpose of this study was to investigate the physical fitness level and the relationship between exercise habituation and physical fitness level in Japanese breast cancer survivors. Fifty breast cancer survivors participated in this study. Participants were assigned to either exercise habituation group (n=25) or non-exercise group (n=25). We evaluated exercise habituation using an original questionnaire and examined various physical fitness level. Body weight, body mass index, and percent body fat were significantly lower in the exercise habituation group than non-exercise group. T-score of cardiorespiratory fitness was significantly higher in the exercise habituation group than average Japanese women. These results suggested that exercise habituation is relative to body weight and cardiorespiratory fitness level in Japanese breast cancer survivors.