Lifestyle, Obesity, and Insulin Resistance
The prevention of diabetes is an urgent worldwide public health concern. The period preceding onset of type 2 diabetes is typically characterized by obesity and insulin resistance induced by overeating and physical inactivity. In the 1970s, Belloc and Breslow (1) presented evidence that physical health is associated with the following seven favorable habits: sleeping 7–8 h, eating breakfast almost every day, avoiding eating between meals, maintaining a desirable weight with respect to height, participating in active sports, limiting alcohol intake, and avoiding smoking cigarettes. We studied the relationships between unhealthy habits and the presence of obesity and insulin resistance.
Subjects consulting the health care center at the First Red Cross Hospital of Kyoto from 1998 to 1999 were recruited. The protocol was approved by the ethics committees of our hospitals. A physical examination, routine biochemical screening tests, and a 75-g oral glucose tolerance test including plasma insulin measurements were performed. We studied 453 subjects (321 men and 131 women, aged 53 ± 10 years). Subjects were free from diabetes and had a BMI of 23.4 ± 3.0. Data were gathered from a self-administered questionnaire completed by all subjects. Habitual patterns were deduced from answers on the questionnaire concerning eating (time spent eating a meal and regularity of meals, including breakfast) and sleep (bedtime and duration of sleep). Obesity was defined as BMI ≥25 kg/m2. Insulin resistance was determined using the R value of the homeostasis model assessment (HOMA) of Matthews et al. (2) and was defined as an HOMA-IR ≥2.0. Logistic regression was used to evaluate associations between lifestyle data and obesity or insulin resistance.
Subjects who ate quickly had 1.8 times the risk for obesity and 1.5 times the risk for insulin resistance compared with subjects who ate more slowly (Table 1). Irregularities in the amount of meals eaten daily (e.g., eating more or fewer than three meals a day or eating between meals) was also associated with increased risk for both obesity and insulin resistance. Skipping breakfast was relatively common among men and carried an increased risk of obesity. As for sleep, sleeplessness beyond midnight and sleeping <6 h were both significant risk factors for obesity, whereas only insufficient amounts of sleep was a significant risk factor for insulin resistance.
Breslow’s seven favorable habits appeared to show promise for the prevention of type 2 diabetes as well as for the promotion of overall physical health. In our study, erratic eating, skipping breakfast, eating between meals, and insufficient sleep (<6 h) were associated with obesity and insulin resistance. Whereas caloric restriction and physical exercise have obvious importance, we stress that actively promoting healthy habits concerning eating and sleeping should be considered for the prevention of obesity and insulin resistance. Individual lifestyle patterns should be analyzed to identify situations in which altering personal habits can counteract obesity, prevent type 2 diabetes, and promote overall good health.
Address correspondence to Hirofumi Shigeta, MD, Department of Internal Medicine, Shyakaihoken Kobe Central Hospital, 2-1-1 Sohyama-cho, Kita-ku, Kobe 651-1145, Japan. E-mail:.