As your body shifts to burning fat as its main source of energy, Dr. Arad explained that your insulin levels are very low. Conversely, "hormones like adiponectin (which regulates sugar and fat metabolism) and growth hormone and epinephrine (commonly referred to as adrenaline) are very high," he said.
Because your insulin levels are low, "our blood vessels expand so there is more flow of nutrients and oxygen to the blood or to the working muscle or to the organs in general. And there are all those different hormones that are increasing just to mobilize fat to provide for energy," Dr. Arad explained.
Dr. Arad said researchers don't know too much about adiponectin yet and explained "it affects the cells' ability to take in sugar and fat and use it for energy, and it affects how and where we store fat." According to Dr. Arad, "Adiponectin levels are affected by lifestyle, namely bodyweight, nutrition, and exercise." He further explained that low adiponectin levels are associated with weight gain, and weight loss is one of the best ways to increase your adiponectin levels.
"All of those hormonal changes that involve, or are associated with, fasting seem to be healthy," said Dr. Arad. Although it isn't definitive as to whether fasting will greatly improve your metabolic rate, some research has shown that it may improve your metabolic rate.
If you're still undecided about beginning intermittent fasting and want to improve your metabolic rate, Dr. Arad said that as long as you follow a healthy diet, don't eat too much, and eat real food, you can reap the health benefits — fasting or not. "On the contrary, people who fast, and do it smartly, can certainly gain a lot of benefits." According to Dr. Arad, "There are a lot of positive effects associated with fasting, as long as it's done very wisely."
Be sure to consult your primary care physician before making any changes to your diet.