Impact of Carbohydrate Intake on Obesity in Japanese Patients with Type 2 Diabetes—An Analysis of the JDCP Registry

While the clinical relevance of a low carbohydrate diet for obese patients with diabetes is still a matter of debate, the optimal amount of carbohydrates has not yet been elucidated. Therefore, we investigated the association between obesity and the carbohydrate intake while considering the physical activity (PA) levels in patients with type 2 diabetes. Japanese patients with type 2 diabetes in a nation-wide registry who completed a lifestyle survey, but were not administered insulin therapy (N=1111, mean age 61.7 y, mean BMI 24.4 kg/m²) were included in this cross-sectional study. The carbohydrate intake and PA were evaluated by the Brief-type self-administered Diet History Questionnaire and the International Physical Activity Questionnaire, respectively. Participants were stratified into two groups according to whether they were above or below the PA of 1380 MET min/week which is the level recommended by the Japan Diabetes Society and WHO, as well as into tertiles according to their carbohydrate intake. The odds ratio (OR) for obesity (defined as BMI ≥25 kg/m²) in each combined category was determined by a multivariate logistic regression model. The mean daily intake of energy, carbohydrate, protein, and fat was 1695 kcal, 233g, 69g, and 44g, respectively, and the median PA was 1386 MET min/week. ORs for obesity in participants whose carbohydrate intake was in the top tertile (≥ 253g/day) and a PA of <1380 MET min/week compared to those whose carbohydrate intake was in the bottom tertile (< 196 g/day) and a PA of ≥ 1380 MET min/week was 1.8 (95% CI, 1.2-2.9, p=0.01). However, the association became non-significant when adjusted by energy intake instead of the amount of fat and protein.

In conclusion, a daily carbohydrate intake of more than approx. 250 g was significantly associated with obesity in combination with an inactive state in Japanese patients with type 2 diabetes, even though the energy intake might have as strong impact as carbohydorate intake.