There’s a belief in our society that aging and a decline in health inevitably go hand-in-hand. Thirty-somethings joking about not being unable to tolerate a hangover as well as a decade before or forty-somethings wondering when the heck their bones started aching every morning certainly aren’t imagining things. And then of course there are the ailments that plague older populations, such as dementia and Parkinson’s.

But according to functional medicine doctor Mark Hyman, MD, author of the new book Food Fix, it’s not impossible to get healthier as you age. It takes a conscious effort to live well, and Dr. Hyman says often comes down to common sense everyday habits such as regular exercise and a predominately healthy diet.

On the food front, Dr. Hyman offers up this important intel on how to live longer, healthfully: “A diet that helps to protect against insulin resistance is the number one factor,” he says. “The main driver of all the diseases related to aging is sugar and starch.” Minimizing consumption of these two ingredients is directly linked to aging well because they are both linked to insulin resistance as well as diabetes, heart disease, cancer, Alzheimer’s, and even depression.

If the idea of protecting against insulin resistance is totally new to you, getting acquainted with the glycemic index is a good tool to use as a guide. The glycemic index is a numerical index or ranking of carbohydrates based on how they impact blood sugar levels when eaten without any other foods. Starchy foods, like those Dr. Hyman avoids, tend to be on the high end of the glycemic index. Maintaining a healthy weight is also linked to protecting against insulin resistance.

Dr. Hyman’s big takeaway is that being mindful of the amount of sugars and starches you eat on a regular basis is the best habit someone can make in terms of healthy aging. Put this tip into practice and you’ll be thanking yourself for many years to come..

Here are some more science-backed tips linked to longevity and foods linked to living longer.