Daily Physical Activity After Meals -long Term Effects On Blood Glucose

Abstract

PURPOSE: The postprandial blood glucose concentration is an important risk factor for development of cardiovascular diseases and diabetes. Previous studies have shown that one bout of moderate or light post-meal physical activity effectively blunts the postprandial increase in blood glucose after carbohydrate intake. Pre-meal exercise does not generate such effect. Thus, the effect of exercise on postprandial glycemia depend on the timing of exercise. Even very light physical activity decreases postprandial glycemia when performed in the postprandial period. The purpose of this study was to investigate whether such activity performed each day for 12 weeks would influence blood variables related to glycemic control. METHODS: 40 subjects being ethnic Norwegians or of South Asian origin were randomized into an intervention or a control group. They were previously diagnosed as hyperglycemic, or with high risk of type 2 diabetes according to Ramachandran’s risc score. Control subjects were told to maintain their usual physical activity patterns during the study period, while the intervention subjects were instructed to undertake a minimum of 30 minutes of daily post-meal physical activity in addition to their usual activity patterns. Venous blood samples were taken before and after the 12 week intervention period. Plasma was analyzed for HbA1c and for fasting and 2hour (OGTT) values of glucose, insulin and c-peptide. The subjects kept a physical activity diary, answered questionnaires and used accelerometers to determine the level of physical activity. RESULTS: The intervention subjects reported an average of 1.3±0,8 bouts of physical activity each day (usual activity included), starting 29±13 min after the last meal, lasting 56±21 min, with an intensity of 11.3±1,0 on Borg RPE scale. This was an increase in post meal physical activity of 41±25 min/day compared to pre intervention (p<0.001). The control group did not change their activity habits. None of the glycemic variables changed from pre to post, neither in the intervention nor the control group (p>0.1). CONCLUSION: This study is not in support of the idea that daily post meal light physical activity might alter glycemia.