Health Matters: What is intermittent fasting?
Dr. Shilpa Ravella: It’s really a way to decrease calories at certain times of the day or week. There are many different ways to do this. For example, you can have an intermittent fast that involves eating whatever you want for five days and then eating a lot fewer calories on two days out of the week. So, about 500 calories on two days and then regular meals the rest of the week. You can also fast every other day, for example, eating 500 calories every other day.
Is it healthy?
Fasting has actually been around for thousands of years and can improve health. From an evolutionary perspective, our habit of eating three meals a day and then snacking, eating while watching TV at night, and having all of these different foods during the day is pretty abnormal. For much of human history, our access to food was very sporadic. Believe it or not, we have fat tissue with energy reserves that can support the body for a week if we’re unable to have access to food.
There have been human and animal studies that have shown that fasting for just two to five days each month can reduce biomarkers (a measurable indicator of some kind of biological state or condition) for things like diabetes, cancer, and heart disease. It lowers insulin as well as a hormone called insulin-like growth factor, or IGF1, which is linked to cancer and diabetes. When you lower insulin and IGF1, cells get out of growth mode and enter a state of maintenance. This maintenance can help with the aging process and decrease disease risk factors. There are also studies that have shown that fasting can help improve symptoms in patients with autoimmune disease, for example.
You’ve talked a bit about the benefits. Any cons?
If you’re going to consume fewer calories, you want to make sure that you eat a very healthy diet to avoid malnutrition. This includes eating fruits, vegetables, whole grains, nuts, and beans. Just smaller portions, basically. And remember to stay well hydrated.
If you’re doing an intermittent fasting program where two days out of the week you’re eating 500 calories, it is not a license that on five days out of the week you can eat a lot of junk food or whatever you want. It’s important to eat a varied diet with lots of fresh fruits and veggies.