Moderate calorie restriction causes temporal changes in the liver and skeletal muscle metabolism, while moderate weight loss affects muscle, reveals study on obese patients.
Led by Dr. Samuel Klein of the Washington University School of Medicine, the study has also revealed that short-term calorie restriction (CR) with a low-carbohydrate diet caused a greater change in liver fat content and metabolic function than short-term CR with a high-carbohydrate diet.
The researcher points out that insulin resistance is the most common metabolic complication associated with obesity, and is associated with an increased risk of developing non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes.
While the consumption of energy-deficit diets is considered to be very significant for obesity treatment, the most appropriate macronutrient composition of diet therapy needed to improve metabolic health remains controversial.
"Our data underscore the complexity of the metabolic effects of calorie restricition with diets that differ in macronutrient composition, and demonstrate differences among organ systems in the response to calorie restriction and subsequent weight loss," said Dr. Klein.
"Our findings help explain the rapid improvement in glucose levels observed after low-calorie diet therapy and bariatric surgery," he added.
During the study, his team randomised 22 obese patients to a high-carbohydrate or low-carbohydrate energy-deficit diet.
A euglycemic-hyperinsulinemic clamp, muscle biopsies, and magnetic resonance spectroscopy were used to determine insulin action, cellular insulin signalling and intrahepatic triglyceride (IHTG) content before the diet therapy, after 48 hours, and after 7 percent weight loss.
Dr. Klein says that his team's efforts showed that short-term CR caused a rapid decrease in IHTG content, an increase in hepatic insulin sensitivity and a decrease in endogenous glucose production rate, while longer-term CR and a moderate 7 percent weight loss improved skeletal muscle insulin sensitivity in conjunction with an increase in cellular insulin signalling.
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.
A research article on the study has been published in the journal Gastroenterology.