Baseline diet modifies the effects of dietary change.

The Dietary Approaches to Stop Hypertension (DASH) eating pattern has been shown to reduce blood pressure (BP) in previous clinical trials. In the PREMIER study, an established behavioural intervention, with or without DASH, promoted greater weight loss than an advice-only control group, but effects of the DASH intervention on BP were weaker. In these analyses, PREMIER data were used to evaluate whether change in dairy product or fruit and vegetable (FV) intake during the first six intervention months impacted changes in weight and/or BP. Study participants were classified as having low or high intakes of dairy products (<1·5 v. ≥1·5 servings/d) and FV (<5 v. ≥5 servings/d) at baseline and 6 months. For dairy products, in particular, participants with higher baseline intakes tended to decrease their intakes during the intervention. In these analyses, subjects consuming <1·5 dairy servings/d at baseline whose intake increased during the intervention lost more weight than those whose intake decreased or remained low throughout (10·6 v. 7·0 pounds (4·8 v. 3·2 kg) lost, respectively, P = 0·002). The same was true for FV intake (11·0 v. 5·9 pounds (5·0 v. 2·7 kg) lost, P < 0·001). We also found synergistic effects of dairy products and FV on weight loss and BP reduction. Specifically, subjects who increased their intakes of dairy products and also consumed ≥5 servings of FV/d lost more weight and had greater reductions in BP than other groups; in addition, higher FV intakes had the greatest benefit to BP among those consuming more dairy products. These results provide evidence that the DASH pattern was most beneficial to individuals whose baseline diet was less consistent with DASH.