¹Department of Medicine III, Okayama University Medical School, Okayama, Japan

²Faculty of Education, Okayama University, Okayama, Japan

³Okayama Southern Institute of Health, Okayama, Japan

⁴Department of Public Health, Okayama University Medical School, Okayama, Japan

Correspondence to: J Wada, Department of Medicine III, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan. E-mail: junwada@md.okayama-u.ac.jp

OBJECTIVE: To investigate whether the changes in IGF-I concentrations after weight reduction in Japanese overweight men are associated with changes in visceral and subcutaneous fat.

DESIGN: Cross-sectional and longitudinal clinical intervention study with exercise education.

SUBJECTS: One-hundred and twelve Japanese overweight men aged 30-59 y (body mass index (BMI) 28.4±2.5 kg/m²) and 33 normal-weight men aged 30-39 y (BMI 22.1±1.5 kg/m²) at baseline. From the participants, 56 randomly selected overweight men (BMI 28.8±2.8) were further enrolled into a 1 y exercise program.

MEASUREMENTS: Fat distribution was evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography scanning at umbilical levels, metabolic parameters and hormones including insulin, leptin and IGF-I at baseline and after 1 y.

RESULTS: In 112 overweight subjects at baseline, insulin (10.5±5.0 µU/ml) and leptin (6.4±3.7 ng/ml) significantly correlated with both V (r=0.260, P=0.0073; r=0.410, P<0.0001) and S areas (r=0.377, P<0.0001; r=0.613, P<0.0001), respectively. IGF-I (156.8±48.7 µU/ml) significantly and negatively correlated with V area (r=-0.242, P=0.0125) and age (r=-0.192, P=0.0480). In normal-weight men aged 30-39 y (n=33) and age-matched subjects (n=30) selected from the 112 overweight men, the serum IGF-I further tightly correlated with V area (r=-0.467, P<0.0001). Visceral fat area and age were independently related to serum IGF-I levels by multiple regression analysis. By intervention with exercise education, 56 overweight subjects showed an increase in daily steps (6224±2781 to 7898±4141 steps/day) and reduction of BMI (28.8±2.8 to 27.7±2.9). IGF-I significantly correlated with V area (r=-0.432, P=0.0009) but not with S area or BMI.

CONCLUSION: The present study indicated a negative correlation between IGF-I levels and visceral fat at baseline as well as an association between the reduction in visceral fat and increase in IGF-I levels after an exercise intervention.

International Journal of Obesity (2002) 26, 361-369. DOI: 10.1038/sj/ijo/0801899

insulin-like growth factor-I (IGF-I); visceral fat; exercise