Short- and Long-Term Effects of Wholegrain Oat Intake on Weight Management and Glucolipid Metabolism in Overweight Type-2 Diabetics: A Randomized Control Trial

Glycemic control and weight reduction are primary goals for the management of overweight and obese type 2 diabetes mellitus (T2DM). Effective management cannot be achieved without an appropriate diet. Our study aimed to evaluate the short- and long-term effects of oat intake and develop a reasonable dietary plan for overweight T2DM patients. A randomized control trial, registered under ClinicalTrials.gov (Identification code: NCT01495052), was carried out among adult T2DM patients. A subgroup of 298 overweight subjects was selected and received a 30-day centralized intervention and 1-year free-living follow-up. Participants were randomly allocated to one of the following four groups. The usual care group (n = 60) received no intervention; the healthy diet group (n = 79) received a low-fat and high-fiber diet ("healthy diet"); the 50 g-oats group (n = 80) and 100 g-oats group (n = 79) received the "healthy diet" with the same amount of cereals replaced by 50 g and 100 g oats respectively. Anthropometric, blood glycemic and lipid variables were measured. For the 30-day intervention, significant differences in the changes of FPG (fasting plasma glucose), PPG (postprandial plasma glucose), HbA1c (glycosylated hemoglobin), HOMA-IR (homeostasis model assessment of insulin resistance), TC (total cholesterol), TG (total triglycerides), and LDL-c (low-density lipoprotein cholesterol) were observed among the four groups. Compared to the healthy diet group, the 50 g-oats group had a bigger reduction in PPG (mean difference (MD): -1.04 mmol/L; 95% CI: -2.03, -0.05) and TC (MD: -0.24 mmol/L; 95% CI: -0.47, -0.01); the 100 g-oats group had a bigger reduction in PPG (MD: -1.48 mmol/L; 95% CI: -2.57, -0.39), HOMA-IR (MD: -1.77 mU·mol/L²; 95% CI: -3.49, -0.05), TC (MD: -0.33 mmol/L; 95% CI: -0.56, -0.10) and LDL-c (MD: -0.22 mmol/L; 95% CI: -0.41, -0.03). In the 1-year follow-up, greater effects in reducing weight (MD: -0.89 kg; 95% CI: -1.56, -0.22), HbA1c (MD: -0.64%; 95% CI: -1.19, -0.09) and TG (MD: -0.70 mmol/L; 95% CI: -1.11, -0.29) were observed in the 100 g-oats group. In conclusion, short- and long-term oat intake had significant effects on controlling hyperglycemia, lowering blood lipid and reducing weight. Our study provided some supportive evidence for recommending oat as a good whole grain selection for overweight diabetics.