Randy Stanberry says he was so obese for most of his life that there weren't enough numbers on the scale to read his true weight.
"I was a prime target for a heart attack," Stanberry said. "Emotionally, I felt like an oddity. I was out of place. My self-esteem was very low because you know people stare and they snicker and they point."
On Stanberry's 50th birthday, he and his wife Suzy embarked on a weight-loss journey together.
In just a year and a half, Randy went from an estimated 405 pounds to 230 -- a loss of 175 pounds. Suzy dropped from a size 20 to a size 6.
Their secret? Forget about quick-fix diet pills or surgery. Instead they each picked up a tiny journal and started writing down everything they ate in a food diary.
"I thought it was just the easiest thing in the world and that's the key; if it's easy we'll do it," Suzy said. "It's more than just a book. It's a way of life. This is almost like our little miracle book."
The Stanberrys were on to something. A new study by Kaiser Permanente found that keeping a food diary can double a person's weight loss.
In the study, 1,700 participants followed a diet rich in fruits, vegetables and low-fat dairy. After six months, those who kept a diary lost an average of 13 pounds; those who didn't lost only 6 pounds.
Doctors who were involved in the study said that food diaries promote increased awareness and accountability about how much dieters are actually eating and drinking.
After the food diary story aired on "GMA" earlier this month, hundreds of viewers wrote in wanting to know how to start a diary the right way.
Lisa from Hutchinson, Kan., wrote: "I know food diaries work well with weight loss but after a few days, I stop keeping one. Please help!"
Tammy from Austin, Texas, told us: "If I learn to eat better and be more aware of what I am eating maybe I can get a hold of my weight."
And viewer Shanon Koenen of Port Orchard, Wash., said her desk job and lack of exercise led to an unwanted extra 40 pounds.
"I have lost 10 pounds but I've hit a wall," she wrote. "I want to get back on track to lose the weight and become more healthy."
"GMA" sent Shanon to Kaiser Permanente in Portland, Ore., to meet with the study's lead doctor, Victor Stevens, and enroll in Food Diary 101.
Getting started is simple:
Step One: Print out a calorie chart. They're available online, in bookstores and on many restaurant Web sites. Here are a few sites to check out: Spark People Calorie Counter, WebMD Diet Assessment, My Pyramid Tracker.
Step Two: Write down everything you eat along with the approximate number of calories, but continue with your current eating habits for two weeks.
Once you have a good idea of your daily caloric intake reduce that number by 500 calories a day and begin your actual weight loss food diary.
"If you reduce your calories by about 500 a day, you'll lose about a pound a week, and that may not seem like a lot, but over six months it really adds up; and when you do it that way it's much easier to keep the weight off," Stevens said.
The average woman should consume 1,200 to 1,800 calories a day, and the average man 1,500 to 2,000 calories a day.
Stevens calls these numbers the "calorie budget" you have for the day.
"You make conscious decisions all through the day about what you will and won't eat," he said. "If you just go on autopilot throughout the day with regard to food, most people in this country gain weight, which is, unfortunately, what two-thirds of the population has done."
Tips for Keeping a Successful Food Diary
Write in a small journal so you can carry it with you.
Measuring food in cups makes it easier to estimate calories.
No need to write down low-calorie vegetables and fruits like lettuce, broccoli or grapefruit -- they don't count.
Eat more frequently but with smaller portions to help stay full.
The Stanberrys say it's important to treat yourself once in a while. And if they are eating out at a restaurant, they choose one with large portions but split them in half.
"It's a lifestyle," Randy said. "We don't call it a diet. It's a change in behavior. This is what we're going to do the rest of our lives."
Stevens says that a food diary works even better if you're dieting with a partner or friend. He also recommends forming a neighborhood group. When other people can see your diary you're more likely to try and be good.
Most importantly, honesty is crucial for this diet to work -- if you eat it, write it down.