They are calorie restrictors, eating only specific amounts of foods that are high in nutrition but low in calories -- foods like vegetables, fruits, and beans.
At almost every meal, they weigh their food and keep detailed records on their laptop of the nutrition and calories they are consuming.
Averill eats about 1,500 calories and McGlothin about 1,900 -- that's about 30 percent less than what the average American consumes.
"In almost every animal species, it has increased life significantly," said Robert N.Butler, a gerontologist, and president of the International Center for Longevity. "If you reduce by about 30 percent, you get 30 additional percent of life."
Averill and McGlothin claim the benefits of calorie restriction are astounding. They share their healthy diet and lifestyle tips as co-authors of a new book, "The CR Way " (Harper Collins).
"My heart and blood vessels are like a person many decades younger," Averill said.
McGlothin said, "Doing calorie restriction, in the way that we do, is like night and day regarding being able to function. I'm 60 years old. I have 20/20 vision. On IQ tests I've improved 30 percent over the last 14 years, it's usually just the opposite."
Some people are taking a different approach to their search for longevity.