Intermittent fasting can promote weight loss and may improve metabolic health over time, via effects on nutrient signaling, circadian biology and the gut microbiome. These effects can take time. Weight loss studies of IF typically involve interventions that last three to six months. For most people in these studies, it takes two to three months to lose 10 pounds, Dr. Krista Varady says. For diabetic or pre-diabetic individuals seeking to change their A1C or blood glucose levels, it usually takes at least three months to see these levels meaningfully change.
In a 2016 study of time-restricted feeding (all calories consumed in an 8-hour window each day) in conjunction with resistance training in healthy males, research participants who followed the fasting program for eight weeks experienced a decrease in fat mass with no significant change in muscle mass. Fasting individuals also experienced a decrease in IGF-1 and an increase in adiponectin, a hormone that can be an insulin sensitizer in the liver and muscle and help improve glucose and fat metabolism.
It’s important to find a diet or metabolic lifestyle intervention that you can incorporate into your lifestyle long term, given the negative impacts of “yo-yo dieting” for most people. Many people would benefit from continuing intermittent fasting long term if possible, Varady says.