If you have ever read any of John Kiefer’s theories on carb back-loading, you know that he is a huge proponent of training in the morning. There is a good reason why training in the morning is advantageous: It may be the time body- builders are most insulin sensitive. In a recent study in the Journal of Diabetes, postprandial glucose turnover in 20 healthy individuals was measured after mixed meals for breakfast, lunch, and dinner at 7 a.m., 1 p.m., and 7 p.m., respectively. Physical activity was similar in all individuals and on all days. The researchers found that after break-fast, glucose was significantly lower and hepatic insulin release was significantly lower at breakfast compared with other meals. Although meal glucose appearance was similar for all meals, suppression of glucose production tended to be lower and insulin sensitivity tended to be higher after breakfast. Increased insulin sensitivity is a huge plus for bodybuilders as 
it accelerates the transport of amino acids into muscle and stimulates protein synthesis in muscles.