An interesting piece from innovations report: "Moderate calorie restriction causes temporal changes in the liver and skeletal muscle metabolism, whereas moderate weight loss affects muscle ... 22 obese patients were randomized to a high-carbohydrate or low-carbohydrate [calorie restricted] diet. ... insulin action, cellular insulin signaling and [liver] triglyceride (IHTG) content [were determined] ... Researchers found that short-term CR caused a rapid decrease in IHTG content, an increase in [liver] insulin sensitivity and a decrease in endogenous glucose production rate, whereas longer-term CR and a moderate 7 percent weight loss improved skeletal muscle insulin sensitivity in conjunction with an increase in cellular insulin signaling. The effect of moderate CR in obese patients with either a low-fat or low-carbohydrate diet on metabolic function is a continuum, with differential effects on specific organ systems." The same sort of result most likely holds in people of normal weight, based on what I know of past research. Some benefits of CR take effect rapidly, some not, and the precise details vary with the details of diet.