L-carnitine is an amino acid (building block for protein),that helps the body to produce energy; the nutrient is also important for proper heart and brain function, muscle movement, and a number of other body processes.  Stuart Galloway, from the University of Stirling (Scotland), and colleagues enrolled 8 lean and 8 overweight/obese men in a 14-day study.   The men received either three grams of L-carnitine, or three grams of glucose per day with their meals. Subjects then underwent an oral glucose tolerance test (OGTT), which involved feeding them 75 grams of glucose, and then measuring the effects.  The team found that blood sugar levels were significantly lower in the L-carnitine group of lean men, as compared to the glucose fed lean men 30 minutes after ingestion.  As well, blood glucose levels were higher in the overweight/obese subjects at 90 minutes after ingesting L-carnitine, as compared to placebo.