If diagnosed with prediabetes—high blood sugar below the diabetes threshold—delay diabetes through eating less, losing weight, and moving more, and recheck blood sugar every six months

No monetary cost, and eating less may save a little money. Do at least 150 minutes a week of moderate-intensity activity such as brisk walking, averaging just over 20 minutes a day. Eat 400–500 fewer kilocalories daily than before. The hard part is sustaining the changes and keeping weight off after losing it. Recheck with a blood test every six months; a fasting glucose test costs around ten to twenty yuan.

The Da Qing study was a clinic-randomized trial in Da Qing, Heilongjiang. It assigned 577 adults with impaired glucose tolerance, a form of prediabetes, to a control group or one of three interventions: diet alone, exercise alone, or both. The intervention lasted 6 years. Six-year cumulative diabetes incidence was 67.7% in controls, 43.8% with diet, 41.1% with exercise, and 46.0% with diet plus exercise. After adjustment for BMI and fasting glucose, diabetes risk was about 31%, 46%, and 42% lower respectively. Reductions were similar in leaner and overweight people, using BMI 25 as the cutoff. At 23 years, cardiovascular mortality in the intervention groups was about 41% lower (HR 0.59, 95% CI 0.36–0.96, the confidence interval), all-cause mortality about 29% lower (HR 0.71, 0.51–0.99), and diabetes incidence about 45% lower (HR 0.55, 0.40–0.76). At 30 years, median diabetes onset was delayed by 3.96 years. Cardiovascular events were about 26% lower (HR 0.74, 0.59–0.92); serious microvascular complications affecting the retina, kidneys, or nerves were about 35% lower (HR 0.65, 0.45–0.95); cardiovascular mortality was about 33% lower (HR 0.67, 0.48–0.94); and all-cause mortality was about 26% lower (HR 0.74, 0.61–0.89). Average life expectancy increased by 1.44 years (0.20–2.68). The US DPP trial randomized 3234 people with elevated blood sugar. The lifestyle group aimed to lose at least 7% of body weight and be active for at least 150 minutes a week. Over an average of 2.8 years, diabetes risk was 58% lower than with placebo (95% CI 48%–66%). The metformin group had a 31% reduction (17%–43%), less than the lifestyle group. At an average of 15 years, the lifestyle group still had a 27% reduction (HR 0.73, 0.65–0.83), but the gap narrowed over time. At a median of 21 years, all-cause mortality did not differ from placebo (HR 1.02, 0.81–1.28), nor did cardiovascular mortality (HR 1.18, 0.77–1.81). Finland's DPS trial randomized 522 overweight people with impaired glucose tolerance. Four-year cumulative diabetes incidence was 11% in the intervention group versus 23% in controls, a 58% risk reduction during the trial. Follow-up continued after individual counseling ended; the reduction remained 43% at a median of 7 years. At an average of 10.6 years, there was no clear difference in all-cause mortality (HR 0.57, 0.21–1.58) or cardiovascular disease (HR 1.04, 0.72–1.51). The Healthy China Action defines prediabetes as fasting glucose from 6.1 to below 7.0 mmol/L, or glucose 2 hours after a glucose drink from 7.8 to below 11.1 mmol/L. It recommends that overweight or obese people lower BMI to or near 24, or lose at least 7% of body weight; reduce total daily energy intake by at least 400–500 kilocalories; and do at least 150 minutes of moderate-intensity activity weekly. Check fasting or 2-hour post-meal glucose every six months.

Pan XR, Li GW, Hu YH, 等 (1997). Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study. Diabetes Care, 20(4), 537-544. https://doi.org/10.2337/diacare.20.4.537；Li G, Zhang P, Wang J, 等 (2014). Cardiovascular mortality, all-cause mortality, and diabetes incidence after lifestyle intervention for people with impaired glucose tolerance in the Da Qing Diabetes Prevention Study: a 23-year follow-up study. Lancet Diabetes & Endocrinology, 2(6), 474-480. https://doi.org/10.1016/S2213-8587(14)70057-9；Gong Q, Zhang P, Wang J, 等 (2019). Morbidity and mortality after lifestyle intervention for people with impaired glucose tolerance: 30-year results of the Da Qing Diabetes Prevention Outcome Study. Lancet Diabetes & Endocrinology, 7(6), 452-461. https://doi.org/10.1016/S2213-8587(19)30093-2；Knowler WC, Barrett-Connor E, Fowler SE, 等 (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. NEJM, 346(6), 393-403. https://doi.org/10.1056/NEJMoa012512；Diabetes Prevention Program Research Group (2015). Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up: the Diabetes Prevention Program Outcomes Study. Lancet Diabetes & Endocrinology, 3(11), 866-875. https://doi.org/10.1016/S2213-8587(15)00291-0；Lee CG, Heckman-Stoddard B, Dabelea D, 等 (2021). Effect of Metformin and Lifestyle Interventions on Mortality in the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study. Diabetes Care, 44(12), 2775-2782. https://doi.org/10.2337/dc21-1046（争议方）；Tuomilehto J, Lindström J, Eriksson JG, 等 (2001). Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. NEJM, 344(18), 1343-1350. https://doi.org/10.1056/NEJM200105033441801；Lindström J, Ilanne-Parikka P, Peltonen M, 等 (2006). Sustained reduction in the incidence of type 2 diabetes by lifestyle intervention: follow-up of the Finnish Diabetes Prevention Study. Lancet, 368(9548), 1673-1679. https://doi.org/10.1016/S0140-6736(06)69701-8；Uusitupa M, Peltonen M, Lindström J, 等 (2009). Ten-year mortality and cardiovascular morbidity in the Finnish Diabetes Prevention Study—secondary analysis of the randomized trial. PLoS ONE, 4(5), e5656. https://doi.org/10.1371/journal.pone.0005656（争议方）；健康中国行动推进委员会 (2019). 健康中国行动（2019—2030年），（十四）糖尿病防治行动（湖南省卫生健康委员会转载）. https://wjw.hunan.gov.cn/wjw/ztzl/knowledge/tzggzcfg/202003/t20200303_11359594.html

Controversy: all three trials found fewer people developing diabetes and later onset, but only Da Qing found lower mortality. Da Qing included only 577 people; the authors acknowledged the small sample because the trial was originally designed to assess diabetes. After the US DPP trial ended, everyone, including the placebo group, was invited to a modified lifestyle course. The Finnish authors said their sample might be too small to detect modest differences. Delaying diabetes is therefore established, while life extension remains uncertain. Mean BMI exceeded 30 in the US and Finnish trials, compared with only 25.7 in Da Qing. Da Qing advised weight loss only for those with BMI above 25, and actual weight loss was modest. The authors thought dietary change and increased activity were the main mechanisms. People who are not overweight should therefore also change their diet and move more. Start by stopping sugary drinks; see Item 7 in this section (avoid sugar-sweetened drinks). For activity, compare with Item 11 (walk 7000–8000 steps a day). For weight targets, see Item 32 (keep BMI at 20–25). For detection, see Section 1, Item 8 (get a fasting blood glucose test once). Metformin also reduces diabetes incidence, but less than lifestyle change; a doctor should decide whether you should take it. The benefit is rated large based on Da Qing's roughly 26% lower all-cause mortality, although the US and Finnish trials did not replicate it. The main beneficiary is you.