Gerald Cleveland, 90, left, and his brother, Robert, 85, diabetics since childhood.

When Robert Cleveland was a boy, in place of a birthday cake his mother wrapped an oatmeal box in colored paper and put candles on top. "I never had any sweets as a child," he said. "Never."

Since he was 5, he has lived within the strict boundaries imposed by diabetes, knowing that if he loosened his grip on the disease it would ravage his body - the terrifying complications, the shortened life span. For years, the only diabetic he knew was the principal of his grammar school, who lost one leg to the disease, and then the other, "and I remember wondering how long it would be before I lost mine."

Then his big brother, Gerald, got diabetes at age 16 and also adopted a set of meticulous lifelong habits. He scribbles sugar readings and insulin doses in a logbook, tests the level of sugar in his system seven or eight times a day, avoids desserts and simple starches, exercises and has always stayed reed-thin. "Even so, I never expected to live to be 50," he said.

Both brothers have done a bit better than that: Gerald turned 90 this month, and Robert will be 86 in March, and they are in fairly good health for their ages. Experts say that they know of no other childhood diabetic who has lived to be as old as Gerald, and no one who has survived with the disease as long as Robert has - almost 81 years.

"My main reason to stay alive," Gerald said, "is to prove to young people there's a way to live with diabetes, to live well."

As diabetes poses a rapidly rising threat to Americans' health, the lives of these brothers from Syracuse offer the ultimate diabetic success story, with telling insights into what is possible, and at what cost. The Clevelands have lived long and healthy lives in part through extraordinary discipline in diet and exercise, but they have also suffered medical complications and harrowing close calls.

Scientists who have tracked the brothers and other long-term diabetes survivors say that while they almost certainly have some genetic advantages, what sets them apart just as clearly are vigilance, hard work, self-sacrifice and determination.

"They're a little bit obsessive about their records and their diets," said Dr. George L. King, research director of the Joslin Diabetes Center in Boston and a professor at Harvard Medical School. He heads a study of people who have lived with diabetes for at least 50 years - more than 400 of them, so far.

They arrive at the center, he said, carrying "years and years of records, sometimes decades," showing medical tests, blood sugar readings, insulin doses, exercise, even daily food consumption. "Most of them do quite a bit of exercise, they are more careful about their health than even most diabetics, and they also have a very positive outlook."

Nearly all of these patients have Type 1 diabetes, also known as juvenile diabetes, which usually develops in childhood. But the lessons learned from them also apply to Type 2 diabetes, a much more common ailment that usually begins in adulthood and is closely associated with obesity, poor diet and lack of exercise. As Americans grow heavier and more sedentary, Type 2 has become the nation's fastest-growing major disease.

Controlling diabetes still demands a rigorous set of daily tasks and choices, but they have become vastly easier in the last few decades, and millions of people manage them well. But millions of others do not, greatly increasing their risk of crippling complications and early death.

Even when the Clevelands were small, doctors understood that a rigidly controlled diet and regular exercise could stabilize blood sugar and reduce the amount of insulin needed. Many people had neither the means nor the mind-set to follow such instructions, but the Clevelands' mother, Henrietta, did, and she taught her boys well.

"The doctor prescribed the diet I should be on, and my mother was most careful about sticking to it," Robert Cleveland said. "There were very few carbohydrates, a quart and a half of milk every day, and there were lots of vegetables and proteins. She weighed everything I ate on a scale. I could have 20 grams of bread at breakfast, which meant I couldn't have a complete slice."

Gerald calls himself a compulsive reader of food ingredient labels, appalled at both the contents of packaged foods and the ignorance of consumers. "I get so frustrated with some people, even some people with diabetes," he said. "They don't look at the labels, they don't know what a carbohydrate is or even really what a sugar is, and they don't understand how the body uses food. You have to understand these things."

Gerald recalls that for his parents, his two brothers, his sister and him, "life revolved around Bob and his diabetes, and all the work that was involved, and the fear and the need to watch out for him."

What makes the longevity of the Clevelands and some other diabetics all the more remarkable is that they lived most of their lives in the dark ages of diabetes care. When they were young, the disease was expected to lop 20 years off their lives. There was none of the modern gadgetry for measuring and controlling it, and the reasonable expectations for diabetics were amputations, blindness, kidney failure and heart disease. 

Yet against immense odds, the Clevelands endured, even thrived, living to have careers, long marriages, children, grandchildren and great-grandchildren.

"To live as long as the Cleveland brothers, through those times when things were so much worse than they are now, is incredible," said Aaron J. Kowalski, scientific program manager at the Juvenile Diabetes Research Foundation. "Yes, it's genetics, but it's discipline, too. It shows what you can do."

The Clevelands arrived at the right time in history, but barely. When they were born, Type 1 diabetes was still a death sentence - within weeks or months in most cases, or in a few years on what amounted to a starvation diet. Type 2 could often be controlled with diet and exercise, but otherwise, it usually led to years of debilitating illness and a shortened life.

Then, in 1922, scientists at the University of Toronto isolated insulin in a form that was effective and safe enough for human use. Suddenly, thousands of people were delivered from the brink of death, but the lives ahead of them were hard. Controlling diabetes was hard and painful work in the early decades, and what would be considered good control today was simply out of reach.

Disposable sterile syringes with fine-gauge needles did not exist; diabetics injected themselves with glass syringes and thick steel needles, reused again and again, and boiled each time to kill germs. Many people developed infections and abscesses from imperfectly sterilized syringes.

"I remember my mother sharpening the needle each time on a whetstone," Robert Cleveland recalled. "But sometimes it was like getting stuck with a knitting needle."

In the early years, the insulin, which was made from ground-up pancreases of pigs and cows, was so loaded with impurities that the doses needed were several times as large as those used today - and the bigger the dose, the more it hurt. The strength of the insulin was also inconsistent at first. Even after a few years, when the product became purer and more predictable, some people suffered serious adverse reactions to it.

Diabetics suffered a roller-coaster effect of blood sugar highs and dangerous lows. Until the development years later of long-acting insulins that allowed more stability, doctors advised patients to interrupt their sleep to inject themselves, rather than let their sugar levels climb through the night.

Though medical laboratories could test blood samples for sugar content, patients and most doctors' offices could not. Instead, they relied on urine tests, which were far less accurate. For decades, the Clevelands and millions of other diabetics heated urine on kitchen stoves, then added a chemical solution that turned various colors depending on the amount of sugar.

Any diabetics who were aggressive about controlling the illness ran a serious risk of taking too much insulin, which can push blood sugar low enough to cause a coma or death. The alternative was to let sugar levels run abnormally high, which over years damages many parts of the body.

Both brothers remain devout about diet and exercise, and have stayed remarkably active. Robert, a former accountant, is still an avid bicyclist. Gerald, who was the assistant schools superintendent in Syracuse, no longer plays tennis, but he regularly attends an exercise class for the elderly.

Despite their caution, diabetes has given them frequent troubles and scares. When Gerald was in his 20's, a fever caused his blood sugar to soar, which, in turn, hindered his body's ability to heal and fight infection. He nearly died before doctors gave him a new drug, penicillin.

Forty years ago, Robert went into a coma from low blood sugar and came near death after a hike in the Colorado Rockies. Just a few weeks ago, Gerald's blood sugar dipped low enough that he grew dizzy and fell in his apartment, and needed five stitches to close a gash on his head.

The Clevelands have developed some of the circulatory and nerve problems in the feet that are so common to diabetics, and both have had some toes amputated. Gerald has undergone several operations for a rare condition, most prevalent in diabetics, that causes the hands to ball into fists.

They also give much of the credit for their longevity to their wives, who helped them stick to the regimen and saved them from low-blood-sugar episodes. Robert's wife of 58 years, Ruth, is a nurse. "She probably knows more about diabetes than anybody I know," he said.

Gerald's wife, Mildred, died in 2002, after 62 years of marriage, but even as she was dying, he said, she kept the habit of checking his skin during the night for the profuse sweat that might signal low blood sugar. "One time when she had basically been bedridden for weeks, she found the strength to get up and go to the kitchen, and she poured orange juice and brought it back and made me drink it," he said.

Both brothers make a point of meeting with younger diabetics, giving them hope and encouragement.

"It hasn't been easy," Gerald said, "but I've had a wonderful life."