Working as a cook in a hot kitchen, Mr Mok Kai Suan used to down eight soft drinks a day to quench his thirst.

"At that time, I didn't know much about diabetes," said Mr Mok, whose late mother also had the chronic illness.

"I didn't know that I should have drunk plain water."

Mr Mok was diagnosed with diabetes when he was about 30, and cut out the sugary drinks from his diet. However, he did not make other changes to his lifestyle, believing that medication would solve the problem."I come from a poor family and we didn't always have much to eat," he said. "So, when I was working in the food business, I would just eat."

Mr Mok, who is now 60, was diagnosed with kidney failure seven years ago. It was this that really made him turn his life around.

Diabetes, which is often a silent illness, can damage the kidneys and result in kidney failure. Other complications include blindness, heart attacks, amputations and even impotence among men.

Prime Minister Lee Hsien Loong had highlighted the issue as a health crisis during his National Day Rally speech on Sunday, where he advised Singaporeans to take care of their health.

"Get a check-up, exercise more, watch your diet, cut down on sugar," Mr Lee said.

"It requires commitment and adjustments to our habits, our lifestyles and diet. But the payoff is large, and it can be done."

However, even those who have healthy lifestyles can be affected by the disease.

Mr Kevin Lim, 40, had a shock when he found out he had diabetes during a health check in June last year, as previous health checks had shown he had a healthy blood sugar level and body mass index.

He also exercised regularly by running and cycling a few times a week. "Even if you are fit and not obese, it can hit you," said the deputy director of an innovation lab at the National Gallery Singapore.

Doctors are still trying to find out the reason for his diabetes, but Mr Lim has kept up his exercise routine while reducing his sugar intake from foods containing wheat, as well as white rice and noodles, and has kept his condition under control.

For those with the condition, the key is to prevent complications by making lifestyle changes, said Dr Tan Chee Eng, an endocrinologist at Gleneagles Hospital.

"A lot (of people) think they need to go on a diet, (they think) it is a short-term thing," Dr Tan said. "But we are talking about eating this way for the rest of their lives."

In some ways, Mr Mok is a success story. Although he has to go for kidney dialysis three times a week, he no longer has problems with high blood pressure.

He now watches his diet - eating in moderation, with the occasional indulgence - and tries to jog or go for brisk walks at least thrice a week. "I used to have to take 50 types of medication a day," he said. "Now, I don't have to take even one."