Effects of exercise training alone vs a combined exercise and nutritional lifestyle intervention on glucose homeostasis in prediabetic individuals: a randomised controlled trial

Randomized, parallel-group controlled trial; 237 sedentary adults aged 45–75 years with impaired fasting glucose (prediabetes) and BMI 25–35 kg/m2; non-smokers; from the Durham, NC area; four 6-month intervention arms: low-amount/moderate-intensity exercise; high-amount/moderate-intensity exercise; high-amount/vigorous-intensity exercise; diet with weight loss plus exercise.

Diet plus exercise produced the strongest improvements in fasting glucose and overall cardiometabolic health; high-amount moderate-intensity exercise alone significantly improved glucose tolerance, achieving about 79% of the glucose-lowering effect of the diet-plus-exercise program; vigorous-intensity exercise alone did not significantly improve glucose tolerance when energy expenditure was matched. For improving glucose tolerance, moderate-intensity exercise was more effective than vigorous-intensity at the same energy expenditure. Among exercise groups, diet/exercise showed the largest improvements across several outcomes; overall, high-volume moderate-intensity exercise may offer a practical alternative to a diet-plus-exercise program for improving glucose homeostasis in people at risk for diabetes, while diet+exercise remains most effective for multiple cardiometabolic outcomes.

No inactive control group; dropout and funding constraints reduced final sample size; adherence varied and was not perfectly matched; differences in contact time (diet counseling) may confound comparisons; participants were preselected for prediabetes, limiting generalizability; results reflect 6-month outcomes.