Does strength training work better against high blood sugar than cardio?

In people with type 2 diabetes and a normal weight (BMI below 25), strength training outperformed cardio alone. In a nine-month study with 186 participants, blood sugar (measured via HbA1c) fell by an average of 0.44 percentage points in the strength training group. That was statistically significant. The cardio group saw a drop of 0.24 percentage points, but that was not significant. Strength training also improved the ratio of muscle to fat mass, which is itself associated with better blood sugar regulation.

In people with overweight or obesity the picture is different. An intensive training schedule of two days per week, combining interval and strength training, did not lower blood sugar significantly more than ordinary lifestyle counselling over twelve weeks. Muscle mass was better preserved, but for blood sugar regulation an energy-restricted diet (5:2) was more effective in this study. With excess weight, it is therefore not a given that training alone will strongly improve blood sugar.

Cardio and strength training together appears to be a broader approach than either type of training on its own. A meta-analysis of 20 studies in people with diabetes and overweight found improvements in HbA1c, blood pressure and inflammatory markers with combined training. The researchers themselves emphasised that the quality of evidence is low and that more rigorous studies are needed. In a shorter study of adults with high cardiovascular risk, no single type of training significantly improved blood glucose in eight weeks, although combined training had the broadest effect on other cardiovascular risk factors.

Strength training works partly through increased glucose transporters in muscle cells, reduced abdominal fat and improved insulin sensitivity. These are plausible mechanisms, but the evidence for them comes mainly from review articles without a statistical summary, not from large clinical trials. How strong this effect is in practice varies between studies.

The conclusion, then, is that strength training has an advantage over cardio alone, but specifically in people with a normal weight. If you have excess weight, the combination of exercise and diet appears to improve blood sugar the most. For the most reliable approach, it is worthwhile to discuss with your healthcare provider which form of training suits your situation and weight.