Across 78 randomized trials (8,452 adults with metabolic syndrome and overweight or obesity), every structured exercise-only intervention lowered systolic and diastolic blood pressure versus control, and resistance training lowered fasting glucose. Among combined programs, exercise plus Mediterranean diet cut waist circumference, moderate-intensity continuous training plus caloric restriction cut triglycerides, and the same training plus a low-carbohydrate diet cut fasting glucose. Exercise and diet effects were additive for waist circumference and triglycerides only; the additive model failed for the other four outcomes.
The practical message is that metabolic syndrome is not one target. Different levers move different components: exercise reliably handles blood pressure, diet-heavy combinations handle waist and lipids, and glucose control seems to favor resistance training or low-carbohydrate pairings. The failure of simple additivity for blood pressure, glucose and HDL hints that exercise and diet interact in ways that a "do both and add the benefits" assumption misses, which matters for anyone setting expectations. The caveats are substantial, though. Certainty of evidence was low to very low for most comparisons, many diet-containing nodes rest on few trials, and the authors rightly refuse to crown a winner. Network meta-analysis leans on indirect comparisons across heterogeneous trials, and these trials measured risk factors, not heart attacks or mortality. Editorially, this is a useful map rather than a verdict: it confirms that combining exercise with dietary change is sensible and flags the specific pairings worth testing head-to-head in adequately powered trials.