Hg (diastolic), were smaller than those seen in hypertension
drug trials and feeding trials (134, 135). However,
epidemiologic data suggest that even changes as
small as 2 mm Hg in systolic blood pressure can decrease
the risk for coronary heart disease by 6% or
stroke by 16% (136). Direct evidence from observational
follow-up of the large hypertension prevention
trials that used sodium reduction counseling suggest
that these small changes in blood pressure can result in
a 30% reduction in cardiovascular disease events and
revascularization in persons with mildly elevated diastolic
blood pressure (137). Reductions in cholesterol
level were also small (about 0.17 mmol/L [5.02 mg/dL]
in total cholesterol level). On the basis of randomized,
controlled trials in primary prevention, a sustained reduction
of 0.6 mmol/L (23.17 mg/dL) in total serum
cholesterol level—an average decrease of 10%—can reduce
coronary heart disease by about 25% (138). However,
it is unclear whether smaller reductions in total
cholesterol level due to dietary changes can affect cardiovascular
disease.
Medium- to high-intensity physical activity counseling
also resulted in small changes in self-reported
physical activity (an increase of about 40 minutes per
week). Evidence suggests that even low-intensity dietary
counseling results in moderate increases in fruit and
vegetable intake (up to 2 servings a day) and small decreases
in dietary fat intake (about 1.5% decrease in
energy intake from total fat). Evidence for low-intensity
physical counseling interventions for increasing selfreported
physical activity was mixed.
Evidence for maintenance of any behavioral or
physiologic effects beyond 12 months was very limited.
The interventions with significant benefit beyond 12
months were all high-intensity counseling interventions
with group, phone, or mail contact throughout the trial.
Most trials for high-intensity interventions that had
follow-up beyond 12 months showed persistent beneficial
changes in adiposity and lipid levels (but not blood
pressure), as well as improvements in self-reported behavioral
outcomes.
Intervention intensity was the most important factor
for differences in effect size among different trials.
However, the effects of counseling intensity could not
be fully disentangled from the risk among the populations
studied. Although trials in populations with
known traditional cardiovascular risk factors or risk
equivalents were excluded, many of the medium- to
high- intensity interventions were conducted in participants
selected for suboptimal lifestyle behaviors or factors
associated with increased cardiovascular disease
(Table 2). In multivariate meta-regression, both intervention
intensity and risk in the population predicted
larger effects. In addition, some participant populations
were volunteers. Exploratory meta-regressions suggested
that use of volunteer participants was also predictive of