[Column] The power of 1 year that sustains 20 years

People with slightly elevated blood sugar but not diabetes are called prediabetic. At this stage, lifestyle changes like weight loss, exercise, and dietary adjustments are typically recommended over medication. The success rate is low. In reality, only slightly over 10 percent of people manage to return their blood sugar to the normal range. However, if I successfully lower my blood sugar by carefully adjusting my lifestyle habits and become part of that small group, what health benefits would I actually gain?

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Research findings indicate that the risk of death or hospitalization due to heart disease is reduced by half after 20 years. This analysis revisited data from participants in the Diabetes Prevention Trial conducted in the U.S. from 1996 to 2001. The original study compared the effects of three interventions on preventing type 2 diabetes in prediabetic individuals: lifestyle changes including diet and exercise, the diabetes medication metformin, and a placebo. The clinical trial results showed that the intensive lifestyle program reduced the incidence of type 2 diabetes by 58 percent within three years compared with the placebo group, while metformin reduced it by 31 percent.

Researchers then followed up with the 2,402 clinical trial participants 20 years later. In the original study, approximately 11 percent of participants had returned to normal blood glucose levels after one year. Twenty years later, these individuals had a 50 percent lower risk of cardiovascular disease death or hospitalization for heart failure compared to those who did not achieve normal levels. This result was adjusted for various characteristics, including whether diabetes developed.

To validate these findings, the research team also tracked and analyzed data from 540 participants in a similar diabetes prevention clinical trial conducted in China. After six years, about 13 percent of them had their blood sugar return to the normal range. Thirty years later, these individuals also had a 51 percent lower risk of dying from heart disease or being hospitalized for it compared to those who never reached normal levels.

These results do not conclusively prove that lowering blood sugar alone halves heart disease risk. Those who achieved normal blood sugar were generally younger to begin with, had better blood sugar and inflammation levels, and tended to be more proactive about healthy behaviors. There is also the limitation that changes in weight, exercise, diet, and alcohol consumption over decades cannot be tracked. Nevertheless, the possibility remains that normalizing blood sugar contributed to reducing cardiovascular disease risk. Indeed, in the study, the group that normalized their blood sugar showed improved insulin sensitivity and a marked reduction in visceral fat and abdominal inflammation, even though weight loss was similar to that of the group that did not achieve normalization.

This study demonstrates the “legacy effect.” It suggests that just one year of focused effort to restore blood sugar to normal levels can yield positive effects lasting 20 to 30 years, potentially protecting blood vessels. Even if blood sugar rises again later or diabetes develops, adjusting lifestyle habits now for current health remains valuable. Keep up the good work in the New Year.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness, and medications. This column was originally published in Korean in Joongang Ilbo on Dec. 18, 2025. -- Ed.